From 789e107a8d979c03418da6379eb747fa8911655d Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Mon, 27 Jan 2025 12:32:20 -0500
Subject: [PATCH 01/15] fix unicode patches during mutation

---
 slither/core/source_mapping/source_mapping.py |  2 +-
 slither/tools/mutator/mutators/AOR.py         |  2 +-
 slither/tools/mutator/mutators/ASOR.py        |  2 +-
 slither/tools/mutator/mutators/BOR.py         |  2 +-
 slither/tools/mutator/mutators/CR.py          |  2 +-
 slither/tools/mutator/mutators/FHR.py         |  2 +-
 slither/tools/mutator/mutators/LIR.py         |  4 ++--
 slither/tools/mutator/mutators/LOR.py         |  2 +-
 slither/tools/mutator/mutators/MIA.py         |  2 +-
 slither/tools/mutator/mutators/MVIE.py        |  4 ++--
 slither/tools/mutator/mutators/MVIV.py        |  4 ++--
 slither/tools/mutator/mutators/MWA.py         |  2 +-
 slither/tools/mutator/mutators/ROR.py         |  2 +-
 slither/tools/mutator/mutators/RR.py          | 10 ++++++----
 slither/tools/mutator/mutators/SBR.py         |  4 ++--
 slither/tools/mutator/mutators/UOR.py         |  2 +-
 16 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/slither/core/source_mapping/source_mapping.py b/slither/core/source_mapping/source_mapping.py
index 355aa5538..61545c8f5 100644
--- a/slither/core/source_mapping/source_mapping.py
+++ b/slither/core/source_mapping/source_mapping.py
@@ -79,7 +79,7 @@ def content(self) -> str:
         # If the compilation unit was not initialized, it means that the set_offset was never called
         # on the corresponding object, which should not happen
         assert self.compilation_unit
-        return self.compilation_unit.core.source_code[self.filename.absolute][self.start : self.end]
+        return self.compilation_unit.core.source_code[self.filename.absolute].encode("utf-8")[self.start : self.end].decode("utf-8")
 
     @property
     def content_hash(self) -> str:
diff --git a/slither/tools/mutator/mutators/AOR.py b/slither/tools/mutator/mutators/AOR.py
index f86e7d3d4..d74c57371 100644
--- a/slither/tools/mutator/mutators/AOR.py
+++ b/slither/tools/mutator/mutators/AOR.py
@@ -74,7 +74,7 @@ def _mutate(self) -> Dict:
                             # Get the string
                             start = node.source_mapping.start
                             stop = start + node.source_mapping.length
-                            old_str = self.in_file_str[start:stop]
+                            old_str = node.source_mapping.content
                             line_no = node.source_mapping.lines
                             if not line_no[0] in self.dont_mutate_line:
                                 # Replace the expression with true
diff --git a/slither/tools/mutator/mutators/ASOR.py b/slither/tools/mutator/mutators/ASOR.py
index 2ff403b38..18beb63c5 100644
--- a/slither/tools/mutator/mutators/ASOR.py
+++ b/slither/tools/mutator/mutators/ASOR.py
@@ -48,7 +48,7 @@ def _mutate(self) -> Dict:
                             if op != ir.expression:
                                 start = node.source_mapping.start
                                 stop = start + node.source_mapping.length
-                                old_str = self.in_file_str[start:stop]
+                                old_str = node.source_mapping.content
                                 line_no = node.source_mapping.lines
                                 if not line_no[0] in self.dont_mutate_line:
                                     # Replace the expression with true
diff --git a/slither/tools/mutator/mutators/BOR.py b/slither/tools/mutator/mutators/BOR.py
index a8720a4b6..fed5319ec 100644
--- a/slither/tools/mutator/mutators/BOR.py
+++ b/slither/tools/mutator/mutators/BOR.py
@@ -31,7 +31,7 @@ def _mutate(self) -> Dict:
                             # Get the string
                             start = node.source_mapping.start
                             stop = start + node.source_mapping.length
-                            old_str = self.in_file_str[start:stop]
+                            old_str = node.source_mapping.content
                             line_no = node.source_mapping.lines
                             if not line_no[0] in self.dont_mutate_line:
                                 # Replace the expression with true
diff --git a/slither/tools/mutator/mutators/CR.py b/slither/tools/mutator/mutators/CR.py
index ebf93bf18..2c1ebc4d9 100644
--- a/slither/tools/mutator/mutators/CR.py
+++ b/slither/tools/mutator/mutators/CR.py
@@ -23,7 +23,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = node.source_mapping.start
                     stop = start + node.source_mapping.length
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     line_no = node.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
                         new_str = "//" + old_str
diff --git a/slither/tools/mutator/mutators/FHR.py b/slither/tools/mutator/mutators/FHR.py
index 028c1916c..c874b489d 100644
--- a/slither/tools/mutator/mutators/FHR.py
+++ b/slither/tools/mutator/mutators/FHR.py
@@ -22,7 +22,7 @@ def _mutate(self) -> Dict:
         for function in self.contract.functions_and_modifiers_declared:
             start = function.source_mapping.start
             stop = start + function.source_mapping.content.find("{")
-            old_str = self.in_file_str[start:stop]
+            old_str = node.source_mapping.content
             line_no = function.source_mapping.lines
             if not line_no[0] in self.dont_mutate_line:
                 for value in function_header_replacements:
diff --git a/slither/tools/mutator/mutators/LIR.py b/slither/tools/mutator/mutators/LIR.py
index fc621829f..d2ad3e5b3 100644
--- a/slither/tools/mutator/mutators/LIR.py
+++ b/slither/tools/mutator/mutators/LIR.py
@@ -36,7 +36,7 @@ def _mutate(self) -> Dict:  # pylint: disable=too-many-branches
                     # Get the string
                     start = variable.source_mapping.start
                     stop = start + variable.source_mapping.length
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     line_no = variable.node_initialization.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
                         for value in literal_replacements:
@@ -67,7 +67,7 @@ def _mutate(self) -> Dict:  # pylint: disable=too-many-branches
                             literal_replacements.append("-1")
                     start = variable.source_mapping.start
                     stop = start + variable.source_mapping.length
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     line_no = variable.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
                         for new_value in literal_replacements:
diff --git a/slither/tools/mutator/mutators/LOR.py b/slither/tools/mutator/mutators/LOR.py
index 2d1535b1a..64285ed77 100644
--- a/slither/tools/mutator/mutators/LOR.py
+++ b/slither/tools/mutator/mutators/LOR.py
@@ -29,7 +29,7 @@ def _mutate(self) -> Dict:
                             # Get the string
                             start = node.source_mapping.start
                             stop = start + node.source_mapping.length
-                            old_str = self.in_file_str[start:stop]
+                            old_str = node.source_mapping.content
                             line_no = node.source_mapping.lines
                             if not line_no[0] in self.dont_mutate_line:
                                 # Replace the expression with true
diff --git a/slither/tools/mutator/mutators/MIA.py b/slither/tools/mutator/mutators/MIA.py
index f29569f63..07946dc55 100644
--- a/slither/tools/mutator/mutators/MIA.py
+++ b/slither/tools/mutator/mutators/MIA.py
@@ -17,7 +17,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = node.expression.source_mapping.start
                     stop = start + node.expression.source_mapping.length
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     line_no = node.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
                         # Replace the expression with true and false
diff --git a/slither/tools/mutator/mutators/MVIE.py b/slither/tools/mutator/mutators/MVIE.py
index ce51792ff..983b7cf15 100644
--- a/slither/tools/mutator/mutators/MVIE.py
+++ b/slither/tools/mutator/mutators/MVIE.py
@@ -24,7 +24,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = variable.source_mapping.start
                     stop = variable.expression.source_mapping.start
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     new_str = old_str[: old_str.find("=")]
                     line_no = variable.node_initialization.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
@@ -44,7 +44,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = variable.source_mapping.start
                     stop = variable.expression.source_mapping.start
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     new_str = old_str[: old_str.find("=")]
                     line_no = variable.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
diff --git a/slither/tools/mutator/mutators/MVIV.py b/slither/tools/mutator/mutators/MVIV.py
index f9e51c553..d51414a7d 100644
--- a/slither/tools/mutator/mutators/MVIV.py
+++ b/slither/tools/mutator/mutators/MVIV.py
@@ -24,7 +24,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = variable.source_mapping.start
                     stop = variable.expression.source_mapping.start
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     new_str = old_str[: old_str.find("=")]
                     line_no = variable.node_initialization.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
@@ -43,7 +43,7 @@ def _mutate(self) -> Dict:
                 if variable.initialized and isinstance(variable.expression, Literal):
                     start = variable.source_mapping.start
                     stop = variable.expression.source_mapping.start
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     new_str = old_str[: old_str.find("=")]
                     line_no = variable.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
diff --git a/slither/tools/mutator/mutators/MWA.py b/slither/tools/mutator/mutators/MWA.py
index 9682f10ca..1ba56b3e1 100644
--- a/slither/tools/mutator/mutators/MWA.py
+++ b/slither/tools/mutator/mutators/MWA.py
@@ -18,7 +18,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = node.source_mapping.start
                     stop = start + node.source_mapping.length
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     line_no = node.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
                         if not isinstance(node.expression, UnaryOperation):
diff --git a/slither/tools/mutator/mutators/ROR.py b/slither/tools/mutator/mutators/ROR.py
index 9daae0663..aea209f4b 100644
--- a/slither/tools/mutator/mutators/ROR.py
+++ b/slither/tools/mutator/mutators/ROR.py
@@ -36,7 +36,7 @@ def _mutate(self) -> Dict:
                                 # Get the string
                                 start = ir.expression.source_mapping.start
                                 stop = start + ir.expression.source_mapping.length
-                                old_str = self.in_file_str[start:stop]
+                                old_str = node.source_mapping.content
                                 line_no = node.source_mapping.lines
                                 if not line_no[0] in self.dont_mutate_line:
                                     # Replace the expression with true
diff --git a/slither/tools/mutator/mutators/RR.py b/slither/tools/mutator/mutators/RR.py
index ba76d657f..d37f2e9b6 100644
--- a/slither/tools/mutator/mutators/RR.py
+++ b/slither/tools/mutator/mutators/RR.py
@@ -21,9 +21,11 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = node.source_mapping.start
                     stop = start + node.source_mapping.length
-                    old_str = self.in_file_str[start:stop]
-                    line_no = node.source_mapping.lines
-                    if not line_no[0] in self.dont_mutate_line:
+                    old_str = node.source_mapping.content
+                    line_no = node.source_mapping.lines[0]
+                    if not line_no in self.dont_mutate_line:
+                        if node.type == NodeType.RETURN and not old_str.lstrip().startswith("return"):
+                            continue # skip the return declarations in fn signatures
                         if not old_str.lstrip().startswith("revert"):
                             new_str = "revert()"
                             create_patch_with_line(
@@ -33,6 +35,6 @@ def _mutate(self) -> Dict:
                                 stop,
                                 old_str,
                                 new_str,
-                                line_no[0],
+                                line_no,
                             )
         return result
diff --git a/slither/tools/mutator/mutators/SBR.py b/slither/tools/mutator/mutators/SBR.py
index efbda4877..18cea69d9 100644
--- a/slither/tools/mutator/mutators/SBR.py
+++ b/slither/tools/mutator/mutators/SBR.py
@@ -64,7 +64,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = node.source_mapping.start
                     stop = start + node.source_mapping.length
-                    old_str = self.in_file_str[start:stop]
+                    old_str = node.source_mapping.content
                     line_no = node.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
                         for value in solidity_rules:
@@ -89,7 +89,7 @@ def _mutate(self) -> Dict:
             if node:
                 start = node.source_mapping.start
                 stop = start + node.source_mapping.length
-                old_str = self.in_file_str[start:stop]
+                old_str = node.source_mapping.content
                 line_no = node.source_mapping.lines
                 if not line_no[0] in self.dont_mutate_line:
                     for value in solidity_rules:
diff --git a/slither/tools/mutator/mutators/UOR.py b/slither/tools/mutator/mutators/UOR.py
index f427c2fbf..bd22f1f37 100644
--- a/slither/tools/mutator/mutators/UOR.py
+++ b/slither/tools/mutator/mutators/UOR.py
@@ -29,7 +29,7 @@ def _mutate(self) -> Dict:
                     continue
                 start = node.source_mapping.start
                 stop = start + node.source_mapping.length
-                old_str = self.in_file_str[start:stop]
+                old_str = node.source_mapping.content
                 line_no = node.source_mapping.lines
                 if not line_no[0] in self.dont_mutate_line:
                     if (

From e31a88196d3a2fe6f33ee88cb606a61163981586 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Mon, 27 Jan 2025 12:34:33 -0500
Subject: [PATCH 02/15] fix mutation logs & RR mutator

---
 slither/tools/mutator/__main__.py    | 15 +++++++++++----
 slither/tools/mutator/mutators/RR.py |  3 ++-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/slither/tools/mutator/__main__.py b/slither/tools/mutator/__main__.py
index d97806e28..f71ef26b5 100644
--- a/slither/tools/mutator/__main__.py
+++ b/slither/tools/mutator/__main__.py
@@ -167,7 +167,10 @@ def main() -> None:  # pylint: disable=too-many-statements,too-many-branches,too
     # get all the contracts as a list from given codebase
     sol_file_list: List[str] = get_sol_file_list(Path(args.codebase), paths_to_ignore_list)
 
-    logger.info(blue("Preparing to mutate files:\n- " + "\n- ".join(sol_file_list)))
+    if not contract_names:
+        logger.info(blue("Preparing to mutate files:\n- " + "\n- ".join(sol_file_list)))
+    else:
+        logger.info(blue("Preparing to mutate contracts:\n- " + "\n- ".join(contract_names)))
 
     # folder where backup files and uncaught mutants are saved
     if output_dir is None:
@@ -240,7 +243,8 @@ def main() -> None:  # pylint: disable=too-many-statements,too-many-branches,too
 
         # perform mutations on {target_contract} in file {file_name}
         # setup placeholder val to signal whether we need to skip if no target_contract is found
-        target_contract = "SLITHER_SKIP_MUTATIONS" if contract_names else ""
+        skip_flag = "SLITHER_SKIP_MUTATIONS"
+        target_contract = skip_flag if contract_names else ""
         try:
             # loop through all contracts in file_name
             for compilation_unit_of_main_file in sl.compilation_units:
@@ -258,8 +262,7 @@ def main() -> None:  # pylint: disable=too-many-statements,too-many-branches,too
                     )
                     continue
 
-                if target_contract == "SLITHER_SKIP_MUTATIONS":
-                    logger.debug(f"Skipping mutations in {filename}")
+                if target_contract == skip_flag:
                     continue
 
                 # TODO: find a more specific way to omit interfaces
@@ -334,6 +337,10 @@ def main() -> None:  # pylint: disable=too-many-statements,too-many-branches,too
         # transfer and delete the backup files
         transfer_and_delete(files_dict)
 
+        if target_contract == skip_flag:
+            logger.debug(f"No target contracts found in {filename}, skipping")
+            continue
+
         # log results for this file
         logger.info(blue(f"Done mutating {target_contract}."))
         if total_mutant_counts[0] > 0:
diff --git a/slither/tools/mutator/mutators/RR.py b/slither/tools/mutator/mutators/RR.py
index d37f2e9b6..174daa671 100644
--- a/slither/tools/mutator/mutators/RR.py
+++ b/slither/tools/mutator/mutators/RR.py
@@ -3,7 +3,6 @@
 from slither.tools.mutator.utils.patch import create_patch_with_line
 from slither.tools.mutator.mutators.abstract_mutator import AbstractMutator
 
-
 class RR(AbstractMutator):  # pylint: disable=too-few-public-methods
     NAME = "RR"
     HELP = "Revert Replacement"
@@ -15,8 +14,10 @@ def _mutate(self) -> Dict:
             for node in function.nodes:
                 if node.type not in (
                     NodeType.ENTRYPOINT,
+                    NodeType.IF,
                     NodeType.ENDIF,
                     NodeType.ENDLOOP,
+                    NodeType.PLACEHOLDER,
                 ):
                     # Get the string
                     start = node.source_mapping.start

From 8b9590dc96e12959a5c743b79af953282b127a06 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Mon, 27 Jan 2025 13:26:03 -0500
Subject: [PATCH 03/15] skip assembly in BOR mutator

---
 slither/tools/mutator/mutators/BOR.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/slither/tools/mutator/mutators/BOR.py b/slither/tools/mutator/mutators/BOR.py
index fed5319ec..d6638daf8 100644
--- a/slither/tools/mutator/mutators/BOR.py
+++ b/slither/tools/mutator/mutators/BOR.py
@@ -35,7 +35,10 @@ def _mutate(self) -> Dict:
                             line_no = node.source_mapping.lines
                             if not line_no[0] in self.dont_mutate_line:
                                 # Replace the expression with true
-                                new_str = f"{old_str.split(ir.type.value)[0]}{op.value}{old_str.split(ir.type.value)[1]}"
+                                halves = old_str.split(ir.type.value)
+                                if len(halves) != 2:
+                                    continue # skip if assembly
+                                new_str = f"{halves[0]}{op.value}{halves[1]}"
                                 create_patch_with_line(
                                     result,
                                     self.in_file,

From 2295939b63103d96bab291829db7ac66d0dda59f Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Mon, 27 Jan 2025 15:21:58 -0500
Subject: [PATCH 04/15] fix bugs in other mutators

---
 slither/tools/mutator/mutators/AOR.py  | 6 ++++--
 slither/tools/mutator/mutators/FHR.py  | 2 +-
 slither/tools/mutator/mutators/MVIE.py | 4 ++--
 slither/tools/mutator/mutators/ROR.py  | 2 +-
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/slither/tools/mutator/mutators/AOR.py b/slither/tools/mutator/mutators/AOR.py
index d74c57371..a9e816f9e 100644
--- a/slither/tools/mutator/mutators/AOR.py
+++ b/slither/tools/mutator/mutators/AOR.py
@@ -77,8 +77,10 @@ def _mutate(self) -> Dict:
                             old_str = node.source_mapping.content
                             line_no = node.source_mapping.lines
                             if not line_no[0] in self.dont_mutate_line:
-                                # Replace the expression with true
-                                new_str = f"{old_str.split(ir.type.value)[0]}{op.value}{old_str.split(ir.type.value)[1]}"
+                                halves = old_str.split(ir.type.value)
+                                if len(halves) != 2:
+                                    continue # skip if assembly
+                                new_str = f"{halves[0]}{op.value}{halves[1]}"
                                 create_patch_with_line(
                                     result,
                                     self.in_file,
diff --git a/slither/tools/mutator/mutators/FHR.py b/slither/tools/mutator/mutators/FHR.py
index c874b489d..c847542ca 100644
--- a/slither/tools/mutator/mutators/FHR.py
+++ b/slither/tools/mutator/mutators/FHR.py
@@ -22,7 +22,7 @@ def _mutate(self) -> Dict:
         for function in self.contract.functions_and_modifiers_declared:
             start = function.source_mapping.start
             stop = start + function.source_mapping.content.find("{")
-            old_str = node.source_mapping.content
+            old_str = function.source_mapping.content
             line_no = function.source_mapping.lines
             if not line_no[0] in self.dont_mutate_line:
                 for value in function_header_replacements:
diff --git a/slither/tools/mutator/mutators/MVIE.py b/slither/tools/mutator/mutators/MVIE.py
index 983b7cf15..be0a80daf 100644
--- a/slither/tools/mutator/mutators/MVIE.py
+++ b/slither/tools/mutator/mutators/MVIE.py
@@ -24,7 +24,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = variable.source_mapping.start
                     stop = variable.expression.source_mapping.start
-                    old_str = node.source_mapping.content
+                    old_str = variable.source_mapping.content
                     new_str = old_str[: old_str.find("=")]
                     line_no = variable.node_initialization.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
@@ -44,7 +44,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = variable.source_mapping.start
                     stop = variable.expression.source_mapping.start
-                    old_str = node.source_mapping.content
+                    old_str = variable.source_mapping.content
                     new_str = old_str[: old_str.find("=")]
                     line_no = variable.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
diff --git a/slither/tools/mutator/mutators/ROR.py b/slither/tools/mutator/mutators/ROR.py
index aea209f4b..8c13ce672 100644
--- a/slither/tools/mutator/mutators/ROR.py
+++ b/slither/tools/mutator/mutators/ROR.py
@@ -40,7 +40,7 @@ def _mutate(self) -> Dict:
                                 line_no = node.source_mapping.lines
                                 if not line_no[0] in self.dont_mutate_line:
                                     # Replace the expression with true
-                                    new_str = f"{old_str.split(ir.type.value)[0]} {op.value} {old_str.split(ir.type.value)[1]}"
+                                    new_str = f"{old_str.split(ir.type.value)[0]}{op.value}{old_str.split(ir.type.value)[1]}"
                                     create_patch_with_line(
                                         result,
                                         self.in_file,

From 5b03e0a153abf66b7ede75ec92a6ef622bfb4d85 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Mon, 27 Jan 2025 15:23:00 -0500
Subject: [PATCH 05/15] try/catch mutant generation

---
 slither/tools/mutator/mutators/abstract_mutator.py    | 11 ++++++++---
 .../tools/mutator/utils/testing_generated_mutant.py   |  4 +---
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/slither/tools/mutator/mutators/abstract_mutator.py b/slither/tools/mutator/mutators/abstract_mutator.py
index 2e99466d9..21ce52ebe 100644
--- a/slither/tools/mutator/mutators/abstract_mutator.py
+++ b/slither/tools/mutator/mutators/abstract_mutator.py
@@ -6,6 +6,7 @@
 from slither.formatters.utils.patches import apply_patch, create_diff
 from slither.tools.mutator.utils.testing_generated_mutant import test_patch
 from slither.core.declarations import Contract
+from slither.utils.colors import red
 
 logger = logging.getLogger("Slither-Mutate")
 
@@ -70,13 +71,17 @@ def __init__(  # pylint: disable=too-many-arguments
 
     @abc.abstractmethod
     def _mutate(self) -> Dict:
-        """TODO Documentation"""
+        """Abstract placeholder, will be overwritten by each mutator"""
         return {}
 
     # pylint: disable=too-many-branches
     def mutate(self) -> Tuple[List[int], List[int], List[int]]:
-        # call _mutate function from different mutators
-        (all_patches) = self._mutate()
+        all_patches: Dict = {}
+        try:
+            # call _mutate function from different mutators
+            (all_patches) = self._mutate()
+        except Exception as e:
+            logger.error(red("%s mutator failed in %s: %s"), self.NAME, self.contract.name, str(e))
         if "patches" not in all_patches:
             logger.debug("No patches found by %s", self.NAME)
             return [0, 0, 0], [0, 0, 0], self.dont_mutate_line
diff --git a/slither/tools/mutator/utils/testing_generated_mutant.py b/slither/tools/mutator/utils/testing_generated_mutant.py
index d484ff68f..d5725485b 100644
--- a/slither/tools/mutator/utils/testing_generated_mutant.py
+++ b/slither/tools/mutator/utils/testing_generated_mutant.py
@@ -109,9 +109,7 @@ def test_patch(  # pylint: disable=too-many-arguments
 
             create_mutant_file(output_folder, file, generator_name)
             logger.info(
-                red(
-                    f"[{generator_name}] Line {patch['line_number']}: '{patch['old_string']}' ==> '{patch['new_string']}' --> UNCAUGHT"
-                )
+                f"[{generator_name}] Line {patch['line_number']}: '{patch['old_string']}' ==> '{patch['new_string']}' --> UNCAUGHT"
             )
             reset_file(file)
 

From 87fb412ea0e87dceeceb7ff8c20a76a556da363a Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Mon, 27 Jan 2025 15:42:13 -0500
Subject: [PATCH 06/15] fix formatting

---
 slither/core/source_mapping/source_mapping.py | 6 +++++-
 slither/tools/mutator/mutators/AOR.py         | 2 +-
 slither/tools/mutator/mutators/BOR.py         | 2 +-
 slither/tools/mutator/mutators/RR.py          | 7 +++++--
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/slither/core/source_mapping/source_mapping.py b/slither/core/source_mapping/source_mapping.py
index 61545c8f5..59d59ad11 100644
--- a/slither/core/source_mapping/source_mapping.py
+++ b/slither/core/source_mapping/source_mapping.py
@@ -79,7 +79,11 @@ def content(self) -> str:
         # If the compilation unit was not initialized, it means that the set_offset was never called
         # on the corresponding object, which should not happen
         assert self.compilation_unit
-        return self.compilation_unit.core.source_code[self.filename.absolute].encode("utf-8")[self.start : self.end].decode("utf-8")
+        return (
+            self.compilation_unit.core.source_code[self.filename.absolute]
+            .encode("utf-8")[self.start : self.end]
+            .decode("utf-8")
+        )
 
     @property
     def content_hash(self) -> str:
diff --git a/slither/tools/mutator/mutators/AOR.py b/slither/tools/mutator/mutators/AOR.py
index a9e816f9e..1e9008efe 100644
--- a/slither/tools/mutator/mutators/AOR.py
+++ b/slither/tools/mutator/mutators/AOR.py
@@ -79,7 +79,7 @@ def _mutate(self) -> Dict:
                             if not line_no[0] in self.dont_mutate_line:
                                 halves = old_str.split(ir.type.value)
                                 if len(halves) != 2:
-                                    continue # skip if assembly
+                                    continue  # skip if assembly
                                 new_str = f"{halves[0]}{op.value}{halves[1]}"
                                 create_patch_with_line(
                                     result,
diff --git a/slither/tools/mutator/mutators/BOR.py b/slither/tools/mutator/mutators/BOR.py
index d6638daf8..2926cf1c0 100644
--- a/slither/tools/mutator/mutators/BOR.py
+++ b/slither/tools/mutator/mutators/BOR.py
@@ -37,7 +37,7 @@ def _mutate(self) -> Dict:
                                 # Replace the expression with true
                                 halves = old_str.split(ir.type.value)
                                 if len(halves) != 2:
-                                    continue # skip if assembly
+                                    continue  # skip if assembly
                                 new_str = f"{halves[0]}{op.value}{halves[1]}"
                                 create_patch_with_line(
                                     result,
diff --git a/slither/tools/mutator/mutators/RR.py b/slither/tools/mutator/mutators/RR.py
index 174daa671..1bcc12e40 100644
--- a/slither/tools/mutator/mutators/RR.py
+++ b/slither/tools/mutator/mutators/RR.py
@@ -3,6 +3,7 @@
 from slither.tools.mutator.utils.patch import create_patch_with_line
 from slither.tools.mutator.mutators.abstract_mutator import AbstractMutator
 
+
 class RR(AbstractMutator):  # pylint: disable=too-few-public-methods
     NAME = "RR"
     HELP = "Revert Replacement"
@@ -25,8 +26,10 @@ def _mutate(self) -> Dict:
                     old_str = node.source_mapping.content
                     line_no = node.source_mapping.lines[0]
                     if not line_no in self.dont_mutate_line:
-                        if node.type == NodeType.RETURN and not old_str.lstrip().startswith("return"):
-                            continue # skip the return declarations in fn signatures
+                        if node.type == NodeType.RETURN and not old_str.lstrip().startswith(
+                            "return"
+                        ):
+                            continue  # skip the return declarations in fn signatures
                         if not old_str.lstrip().startswith("revert"):
                             new_str = "revert()"
                             create_patch_with_line(

From af8e5cfb05d28a13669e54c9c118fb77c75daf98 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Mon, 27 Jan 2025 15:52:29 -0500
Subject: [PATCH 07/15] bugfixes & fix pylint

---
 slither/tools/mutator/mutators/LIR.py              | 4 ++--
 slither/tools/mutator/mutators/MVIV.py             | 4 ++--
 slither/tools/mutator/mutators/abstract_mutator.py | 1 +
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/slither/tools/mutator/mutators/LIR.py b/slither/tools/mutator/mutators/LIR.py
index d2ad3e5b3..46d816e26 100644
--- a/slither/tools/mutator/mutators/LIR.py
+++ b/slither/tools/mutator/mutators/LIR.py
@@ -36,7 +36,7 @@ def _mutate(self) -> Dict:  # pylint: disable=too-many-branches
                     # Get the string
                     start = variable.source_mapping.start
                     stop = start + variable.source_mapping.length
-                    old_str = node.source_mapping.content
+                    old_str = variable.source_mapping.content
                     line_no = variable.node_initialization.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
                         for value in literal_replacements:
@@ -67,7 +67,7 @@ def _mutate(self) -> Dict:  # pylint: disable=too-many-branches
                             literal_replacements.append("-1")
                     start = variable.source_mapping.start
                     stop = start + variable.source_mapping.length
-                    old_str = node.source_mapping.content
+                    old_str = variable.source_mapping.content
                     line_no = variable.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
                         for new_value in literal_replacements:
diff --git a/slither/tools/mutator/mutators/MVIV.py b/slither/tools/mutator/mutators/MVIV.py
index d51414a7d..1e14d1177 100644
--- a/slither/tools/mutator/mutators/MVIV.py
+++ b/slither/tools/mutator/mutators/MVIV.py
@@ -24,7 +24,7 @@ def _mutate(self) -> Dict:
                     # Get the string
                     start = variable.source_mapping.start
                     stop = variable.expression.source_mapping.start
-                    old_str = node.source_mapping.content
+                    old_str = variable.source_mapping.content
                     new_str = old_str[: old_str.find("=")]
                     line_no = variable.node_initialization.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
@@ -43,7 +43,7 @@ def _mutate(self) -> Dict:
                 if variable.initialized and isinstance(variable.expression, Literal):
                     start = variable.source_mapping.start
                     stop = variable.expression.source_mapping.start
-                    old_str = node.source_mapping.content
+                    old_str = variable.source_mapping.content
                     new_str = old_str[: old_str.find("=")]
                     line_no = variable.source_mapping.lines
                     if not line_no[0] in self.dont_mutate_line:
diff --git a/slither/tools/mutator/mutators/abstract_mutator.py b/slither/tools/mutator/mutators/abstract_mutator.py
index 21ce52ebe..1c7274407 100644
--- a/slither/tools/mutator/mutators/abstract_mutator.py
+++ b/slither/tools/mutator/mutators/abstract_mutator.py
@@ -77,6 +77,7 @@ def _mutate(self) -> Dict:
     # pylint: disable=too-many-branches
     def mutate(self) -> Tuple[List[int], List[int], List[int]]:
         all_patches: Dict = {}
+        # pylint: disable=broad-exception-caught
         try:
             # call _mutate function from different mutators
             (all_patches) = self._mutate()

From 9fbb9aa4c519391667b610091cab17ad10af7724 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Wed, 5 Feb 2025 15:20:59 -0500
Subject: [PATCH 08/15] revert byte conversion in Source.content

---
 slither/core/source_mapping/source_mapping.py | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/slither/core/source_mapping/source_mapping.py b/slither/core/source_mapping/source_mapping.py
index 59d59ad11..355aa5538 100644
--- a/slither/core/source_mapping/source_mapping.py
+++ b/slither/core/source_mapping/source_mapping.py
@@ -79,11 +79,7 @@ def content(self) -> str:
         # If the compilation unit was not initialized, it means that the set_offset was never called
         # on the corresponding object, which should not happen
         assert self.compilation_unit
-        return (
-            self.compilation_unit.core.source_code[self.filename.absolute]
-            .encode("utf-8")[self.start : self.end]
-            .decode("utf-8")
-        )
+        return self.compilation_unit.core.source_code[self.filename.absolute][self.start : self.end]
 
     @property
     def content_hash(self) -> str:

From 84011e4a52b2c465b2d383b93ce9dbbd9c83d222 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Fri, 7 Feb 2025 12:27:28 -0500
Subject: [PATCH 09/15] fix source_mapping.content to handle byte offsets

---
 slither/core/source_mapping/source_mapping.py | 11 ++++++++--
 slither/tools/documentation/__main__.py       | 22 +++++++++----------
 slither/tools/flattening/flattening.py        |  7 ++++++
 3 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/slither/core/source_mapping/source_mapping.py b/slither/core/source_mapping/source_mapping.py
index 355aa5538..afa8e83a9 100644
--- a/slither/core/source_mapping/source_mapping.py
+++ b/slither/core/source_mapping/source_mapping.py
@@ -73,13 +73,20 @@ def content(self) -> str:
         """
         Return the txt content of the Source
 
-        Returns:
+        Use this property instead of eg source_code[start:end]
+        Above will return incorrect content if source_code contains any unicode
+        because self.start and self.end are byte offsets, not char offsets
 
+        Returns: str
         """
         # If the compilation unit was not initialized, it means that the set_offset was never called
         # on the corresponding object, which should not happen
         assert self.compilation_unit
-        return self.compilation_unit.core.source_code[self.filename.absolute][self.start : self.end]
+        return (
+            self.compilation_unit.core.source_code[self.filename.absolute]
+                .encode("utf-8")[self.start : self.end]
+                .decode("utf-8")
+        )
 
     @property
     def content_hash(self) -> str:
diff --git a/slither/tools/documentation/__main__.py b/slither/tools/documentation/__main__.py
index 0244dd6c6..161b2724b 100644
--- a/slither/tools/documentation/__main__.py
+++ b/slither/tools/documentation/__main__.py
@@ -154,15 +154,15 @@ def _handle_function(
     ):
         return overwrite
     prompt = "Create a natpsec documentation for this solidity code with only notice and dev.\n"
-    src_mapping = function.source_mapping
-    content = function.compilation_unit.core.source_code[src_mapping.filename.absolute]
-    start = src_mapping.start
-    end = src_mapping.start + src_mapping.length
-    prompt += content[start:end]
-
-    use_tab = _use_tab(content[start - 1])
-    if use_tab is None and src_mapping.starting_column > 1:
-        logger.info(f"Non standard space indentation found {content[start - 1:end]}")
+    srcmap = function.source_mapping
+    src = compilation_unit.core.source_code[srcmap.filename.absolute]
+    first_char_index = len(src.encode("utf-8")[:srcmap.start].decode("utf-8")) # convert byte offset to char offset
+    prev_char = src[prev_char_index - 1] 
+    prompt += srcmap.content
+
+    use_tab = _use_tab(prev_char)
+    if use_tab is None and srcmap.starting_column > 1:
+        logger.info(f"Non standard indentation found: '{first_char}'")
         if overwrite:
             logger.info("Disable overwrite to avoid mistakes")
             overwrite = False
@@ -189,7 +189,7 @@ def _handle_function(
         if logging_file:
             codex.log_codex(logging_file, "A: " + str(answer))
 
-        answer_processed = _handle_codex(answer, src_mapping.starting_column, use_tab, force)
+        answer_processed = _handle_codex(answer, srcmap.starting_column, use_tab, force)
         if answer_processed:
             break
 
@@ -201,7 +201,7 @@ def _handle_function(
     if not answer_processed:
         return overwrite
 
-    create_patch(all_patches, src_mapping.filename.absolute, start, start, "", answer_processed)
+    create_patch(all_patches, srcmap.filename.absolute, srcmap.start, srcmap.start, "", answer_processed)
 
     return overwrite
 
diff --git a/slither/tools/flattening/flattening.py b/slither/tools/flattening/flattening.py
index 182333d3f..ace14d09d 100644
--- a/slither/tools/flattening/flattening.py
+++ b/slither/tools/flattening/flattening.py
@@ -107,6 +107,7 @@ def _get_source_code(
         :return:
         """
         src_mapping = contract.source_mapping
+        # TODO: this needs to be encoded before it gets indexed!
         content = self._compilation_unit.core.source_code[src_mapping.filename.absolute]
         start = src_mapping.start
         end = src_mapping.start + src_mapping.length
@@ -211,6 +212,12 @@ def _get_source_code(
 
         to_patch.sort(key=lambda x: x.index, reverse=True)
 
+        # Note: foundry and solc and everything else return srcmap offsets per-byte
+        # and it seems the rest of slither operates on bytes also
+        # it might just be the mutator and flattener that are incorrectly applying offsets directly to strings
+        # I think I just need to do the following (and similar for mutations)
+        # content = content.encode("utf-8")[start:end].decode("utf-8")
+
         content = content[start:end]
         for patch in to_patch:
             patch_type = patch.patch_type

From 172cdbb1eeeac09a52657f6b0317929a5efbbbb0 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Fri, 7 Feb 2025 14:18:29 -0500
Subject: [PATCH 10/15] fix source_code access in documentation + flattening
 tools

---
 slither/tools/documentation/__main__.py |  8 ++---
 slither/tools/flattening/flattening.py  | 45 ++++++++++++-------------
 2 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/slither/tools/documentation/__main__.py b/slither/tools/documentation/__main__.py
index 161b2724b..417e4f09a 100644
--- a/slither/tools/documentation/__main__.py
+++ b/slither/tools/documentation/__main__.py
@@ -155,14 +155,14 @@ def _handle_function(
         return overwrite
     prompt = "Create a natpsec documentation for this solidity code with only notice and dev.\n"
     srcmap = function.source_mapping
-    src = compilation_unit.core.source_code[srcmap.filename.absolute]
-    first_char_index = len(src.encode("utf-8")[:srcmap.start].decode("utf-8")) # convert byte offset to char offset
-    prev_char = src[prev_char_index - 1] 
+    src = function.compilation_unit.core.source_code[srcmap.filename.absolute]
+    first_char_index = len(src.encode("utf8")[:srcmap.start].decode("utf8")) # convert byte offset to char offset
+    prev_char = src[first_char_index - 1]
     prompt += srcmap.content
 
     use_tab = _use_tab(prev_char)
     if use_tab is None and srcmap.starting_column > 1:
-        logger.info(f"Non standard indentation found: '{first_char}'")
+        logger.info(f"Non standard indentation found: '{prev_char}'")
         if overwrite:
             logger.info("Disable overwrite to avoid mistakes")
             overwrite = False
diff --git a/slither/tools/flattening/flattening.py b/slither/tools/flattening/flattening.py
index ace14d09d..858a83c1f 100644
--- a/slither/tools/flattening/flattening.py
+++ b/slither/tools/flattening/flattening.py
@@ -108,9 +108,7 @@ def _get_source_code(
         """
         src_mapping = contract.source_mapping
         # TODO: this needs to be encoded before it gets indexed!
-        content = self._compilation_unit.core.source_code[src_mapping.filename.absolute]
-        start = src_mapping.start
-        end = src_mapping.start + src_mapping.length
+        src_bytes = self._compilation_unit.core.source_code[src_mapping.filename.absolute]
 
         to_patch = []
         # interface must use external
@@ -125,8 +123,8 @@ def _get_source_code(
                         + f.parameters_src().source_mapping.length
                     )
                     attributes_end = f.returns_src().source_mapping.start
-                    attributes = content[attributes_start:attributes_end]
-                    regex = re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes)
+                    attributes = src_bytes[attributes_start:attributes_end]
+                    regex = re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes.decode("utf8"))
                     if regex:
                         to_patch.append(
                             Patch(
@@ -135,13 +133,13 @@ def _get_source_code(
                             )
                         )
                     else:
-                        raise SlitherException(f"External keyword not found {f.name} {attributes}")
+                        raise SlitherException(f"External keyword not found {f.name} {attributes.decode("utf8")}")
 
                     for var in f.parameters:
                         if var.location == "calldata":
                             calldata_start = var.source_mapping.start
                             calldata_end = calldata_start + var.source_mapping.length
-                            calldata_idx = content[calldata_start:calldata_end].find(" calldata ")
+                            calldata_idx = src_bytes[calldata_start:calldata_end].find(" calldata ")
                             to_patch.append(
                                 Patch(
                                     calldata_start + calldata_idx + 1,
@@ -159,11 +157,11 @@ def _get_source_code(
                         + f.parameters_src().source_mapping["length"]
                     )
                     attributes_end = f.returns_src().source_mapping["start"]
-                    attributes = content[attributes_start:attributes_end]
+                    attributes = src_bytes[attributes_start:attributes_end]
                     regex = (
-                        re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes)
+                        re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes.decode("utf8"))
                         if visibility == "external"
-                        else re.search(r"((\spublic)\s+)|(\spublic)$|(\)public)$", attributes)
+                        else re.search(r"((\spublic)\s+)|(\spublic)$|(\)public)$", attributes.decode("utf8"))
                     )
                     if regex:
                         to_patch.append(
@@ -176,7 +174,7 @@ def _get_source_code(
                         )
                     else:
                         raise SlitherException(
-                            f"{visibility} keyword not found {f.name} {attributes}"
+                            f"{visibility} keyword not found {f.name} {attributes.decode("utf8")}"
                         )
 
         if self._private_to_internal:
@@ -184,8 +182,8 @@ def _get_source_code(
                 if variable.visibility == "private":
                     attributes_start = variable.source_mapping.start
                     attributes_end = attributes_start + variable.source_mapping.length
-                    attributes = content[attributes_start:attributes_end]
-                    regex = re.search(r" private ", attributes)
+                    attributes = src_bytes[attributes_start:attributes_end]
+                    regex = re.search(r" private ", attributes.decode("utf8"))
                     if regex:
                         to_patch.append(
                             Patch(
@@ -195,7 +193,7 @@ def _get_source_code(
                         )
                     else:
                         raise SlitherException(
-                            f"private keyword not found {variable.name} {attributes}"
+                            f"private keyword not found {variable.name} {attributes.decode("utf8")}"
                         )
 
         if self._remove_assert:
@@ -216,28 +214,29 @@ def _get_source_code(
         # and it seems the rest of slither operates on bytes also
         # it might just be the mutator and flattener that are incorrectly applying offsets directly to strings
         # I think I just need to do the following (and similar for mutations)
-        # content = content.encode("utf-8")[start:end].decode("utf-8")
+        # content = content.encode("utf8")[start:end].decode("utf8")
 
-        content = content[start:end]
+        content = src_mapping.content.encode("utf8")
+        start = src_mapping.start
         for patch in to_patch:
             patch_type = patch.patch_type
             index = patch.index
             index = index - start
             if patch_type == "public_to_external":
-                content = content[:index] + "public" + content[index + len("external") :]
+                content = content[:index].decode("utf8") + "public" + content[index + len("external") :].decode("utf8")
             elif patch_type == "external_to_internal":
-                content = content[:index] + "internal" + content[index + len("external") :]
+                content = content[:index].decode("utf8") + "internal" + content[index + len("external") :].decode("utf8")
             elif patch_type == "public_to_internal":
-                content = content[:index] + "internal" + content[index + len("public") :]
+                content = content[:index].decode("utf8") + "internal" + content[index + len("public") :].decode("utf8")
             elif patch_type == "private_to_internal":
-                content = content[:index] + "internal" + content[index + len("private") :]
+                content = content[:index].decode("utf8") + "internal" + content[index + len("private") :].decode("utf8")
             elif patch_type == "calldata_to_memory":
-                content = content[:index] + "memory" + content[index + len("calldata") :]
+                content = content[:index].decode("utf8") + "memory" + content[index + len("calldata") :].decode("utf8")
             else:
                 assert patch_type == "line_removal"
-                content = content[:index] + " // " + content[index:]
+                content = content[:index].decode("utf8") + " // " + content[index:].decode("utf8")
 
-        self._source_codes[contract] = content
+        self._source_codes[contract] = content.decode("utf8")
 
     def _pragmas(self) -> str:
         """

From 738aa96f050d6796a3b6e32bfdd142753153329f Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Fri, 7 Feb 2025 14:18:59 -0500
Subject: [PATCH 11/15] clean up utf8 strings

---
 slither/analyses/evm/convert.py                           | 8 ++++----
 slither/core/source_mapping/source_mapping.py             | 4 ++--
 slither/detectors/source/rtlo.py                          | 6 +++---
 slither/formatters/attributes/const_functions.py          | 2 +-
 slither/formatters/functions/external_function.py         | 6 +++---
 slither/formatters/variables/unchanged_state_variables.py | 2 +-
 slither/formatters/variables/unused_state_variables.py    | 6 +++---
 slither/slithir/convert.py                                | 2 +-
 slither/tools/mutator/mutators/abstract_mutator.py        | 1 -
 slither/tools/mutator/utils/testing_generated_mutant.py   | 8 ++++----
 slither/tools/read_storage/__main__.py                    | 2 +-
 slither/utils/function.py                                 | 4 ++--
 slither/utils/output.py                                   | 2 +-
 slither/utils/standard_libraries.py                       | 2 +-
 slither/visitors/expression/constants_folding.py          | 2 +-
 15 files changed, 28 insertions(+), 29 deletions(-)

diff --git a/slither/analyses/evm/convert.py b/slither/analyses/evm/convert.py
index fe294798e..cb01fbb85 100644
--- a/slither/analyses/evm/convert.py
+++ b/slither/analyses/evm/convert.py
@@ -133,12 +133,12 @@ def _get_evm_instructions_node(node_info):
     contract_file = (
         node_info["slither"]
         .source_code[node_info["contract"].source_mapping.filename.absolute]
-        .encode("utf-8")
+        .encode("utf8")
     )
 
     # Get evm instructions corresponding to node's source line number
     node_source_line = (
-        contract_file[0 : node_info["node"].source_mapping.start].count("\n".encode("utf-8")) + 1
+        contract_file[0 : node_info["node"].source_mapping.start].count("\n".encode("utf8")) + 1
     )
     node_pcs = contract_pcs.get(node_source_line, [])
     node_ins = []
@@ -169,7 +169,7 @@ def generate_source_to_evm_ins_mapping(evm_instructions, srcmap_runtime, slither
     """
 
     source_to_evm_mapping = {}
-    file_source = slither.source_code[filename].encode("utf-8")
+    file_source = slither.source_code[filename].encode("utf8")
     prev_mapping = []
 
     for idx, mapping in enumerate(srcmap_runtime):
@@ -193,7 +193,7 @@ def generate_source_to_evm_ins_mapping(evm_instructions, srcmap_runtime, slither
             # See https://github.com/ethereum/solidity/issues/6119#issuecomment-467797635
             continue
 
-        line_number = file_source[0 : int(offset)].count("\n".encode("utf-8")) + 1
+        line_number = file_source[0 : int(offset)].count("\n".encode("utf8")) + 1
 
         # Append evm instructions to the corresponding source line number
         # Note: Some evm instructions in mapping are not necessarily in program execution order
diff --git a/slither/core/source_mapping/source_mapping.py b/slither/core/source_mapping/source_mapping.py
index afa8e83a9..fbb7279a2 100644
--- a/slither/core/source_mapping/source_mapping.py
+++ b/slither/core/source_mapping/source_mapping.py
@@ -84,8 +84,8 @@ def content(self) -> str:
         assert self.compilation_unit
         return (
             self.compilation_unit.core.source_code[self.filename.absolute]
-                .encode("utf-8")[self.start : self.end]
-                .decode("utf-8")
+                .encode("utf8")[self.start : self.end]
+                .decode("utf8")
         )
 
     @property
diff --git a/slither/detectors/source/rtlo.py b/slither/detectors/source/rtlo.py
index b020f69f9..b9bc7aa74 100644
--- a/slither/detectors/source/rtlo.py
+++ b/slither/detectors/source/rtlo.py
@@ -57,16 +57,16 @@ class RightToLeftOverride(AbstractDetector):
 
     WIKI_RECOMMENDATION = "Special control characters must not be allowed."
 
-    RTLO_CHARACTER_ENCODED = "\u202e".encode("utf-8")
+    RTLO_CHARACTER_ENCODED = "\u202e".encode("utf8")
     STANDARD_JSON = False
 
     def _detect(self) -> List[Output]:
         results = []
-        pattern = re.compile(".*\u202e.*".encode("utf-8"))
+        pattern = re.compile(".*\u202e.*".encode("utf8"))
 
         for filename, source in self.slither.source_code.items():
             # Attempt to find all RTLO characters in this source file.
-            original_source_encoded = source.encode("utf-8")
+            original_source_encoded = source.encode("utf8")
             start_index = 0
 
             # Keep searching all file contents for the character.
diff --git a/slither/formatters/attributes/const_functions.py b/slither/formatters/attributes/const_functions.py
index feb404f7b..3ce5c001e 100644
--- a/slither/formatters/attributes/const_functions.py
+++ b/slither/formatters/attributes/const_functions.py
@@ -43,7 +43,7 @@ def _patch(
     in_file_str = compilation_unit.core.source_code[in_file].encode("utf8")
     old_str_of_interest = in_file_str[modify_loc_start:modify_loc_end]
     # Find the keywords view|pure|constant and remove them
-    m = re.search("(view|pure|constant)", old_str_of_interest.decode("utf-8"))
+    m = re.search("(view|pure|constant)", old_str_of_interest.decode("utf8"))
     if m:
         create_patch(
             result,
diff --git a/slither/formatters/functions/external_function.py b/slither/formatters/functions/external_function.py
index 66dbc4367..de60fa7a7 100644
--- a/slither/formatters/functions/external_function.py
+++ b/slither/formatters/functions/external_function.py
@@ -32,16 +32,16 @@ def _patch(
     old_str_of_interest = in_file_str[modify_loc_start:modify_loc_end]
     # Search for 'public' keyword which is in-between the function name and modifier name (if present)
     # regex: 'public' could have spaces around or be at the end of the line
-    m = re.search(r"((\spublic)\s+)|(\spublic)$|(\)public)$", old_str_of_interest.decode("utf-8"))
+    m = re.search(r"((\spublic)\s+)|(\spublic)$|(\)public)$", old_str_of_interest.decode("utf8"))
     if m is None:
         # No visibility specifier exists; public by default.
         create_patch(
             result,
             in_file,
             # start after the function definition's closing paranthesis
-            modify_loc_start + len(old_str_of_interest.decode("utf-8").split(")")[0]) + 1,
+            modify_loc_start + len(old_str_of_interest.decode("utf8").split(")")[0]) + 1,
             # end is same as start because we insert the keyword `external` at that location
-            modify_loc_start + len(old_str_of_interest.decode("utf-8").split(")")[0]) + 1,
+            modify_loc_start + len(old_str_of_interest.decode("utf8").split(")")[0]) + 1,
             "",
             " external",
         )  # replace_text is `external`
diff --git a/slither/formatters/variables/unchanged_state_variables.py b/slither/formatters/variables/unchanged_state_variables.py
index c7c8bf003..cb880d997 100644
--- a/slither/formatters/variables/unchanged_state_variables.py
+++ b/slither/formatters/variables/unchanged_state_variables.py
@@ -41,7 +41,7 @@ def _patch(  # pylint: disable=too-many-arguments
     old_str_of_interest = in_file_str[modify_loc_start:modify_loc_end]
     # Add keyword `constant` before the variable name
     (new_str_of_interest, num_repl) = re.subn(
-        match_text, replace_text, old_str_of_interest.decode("utf-8"), 1
+        match_text, replace_text, old_str_of_interest.decode("utf8"), 1
     )
     if num_repl != 0:
         create_patch(
diff --git a/slither/formatters/variables/unused_state_variables.py b/slither/formatters/variables/unused_state_variables.py
index 90009c7f1..5b1b391eb 100644
--- a/slither/formatters/variables/unused_state_variables.py
+++ b/slither/formatters/variables/unused_state_variables.py
@@ -22,8 +22,8 @@ def _patch(
     in_file_str = compilation_unit.core.source_code[in_file].encode("utf8")
     old_str_of_interest = in_file_str[modify_loc_start:]
     old_str = (
-        old_str_of_interest.decode("utf-8").partition(";")[0]
-        + old_str_of_interest.decode("utf-8").partition(";")[1]
+        old_str_of_interest.decode("utf8").partition(";")[0]
+        + old_str_of_interest.decode("utf8").partition(";")[1]
     )
 
     create_patch(
@@ -31,7 +31,7 @@ def _patch(
         in_file,
         int(modify_loc_start),
         # Remove the entire declaration until the semicolon
-        int(modify_loc_start + len(old_str_of_interest.decode("utf-8").partition(";")[0]) + 1),
+        int(modify_loc_start + len(old_str_of_interest.decode("utf8").partition(";")[0]) + 1),
         old_str,
         "",
     )
diff --git a/slither/slithir/convert.py b/slither/slithir/convert.py
index cc27eb286..8951707ff 100644
--- a/slither/slithir/convert.py
+++ b/slither/slithir/convert.py
@@ -196,7 +196,7 @@ def _fits_under_byte(val: Union[int, str]) -> List[str]:
         size = len(hex_val) // 2
         return [f"bytes{size}"]
     # val is a str
-    length = len(val.encode("utf-8"))
+    length = len(val.encode("utf8"))
     return [f"bytes{f}" for f in range(length, 33)] + ["bytes"]
 
 
diff --git a/slither/tools/mutator/mutators/abstract_mutator.py b/slither/tools/mutator/mutators/abstract_mutator.py
index 1c7274407..cfeee9759 100644
--- a/slither/tools/mutator/mutators/abstract_mutator.py
+++ b/slither/tools/mutator/mutators/abstract_mutator.py
@@ -47,7 +47,6 @@ def __init__(  # pylint: disable=too-many-arguments
         self.output_folder = output_folder
         self.contract = contract_instance
         self.in_file = self.contract.source_mapping.filename.absolute
-        self.in_file_str = self.contract.compilation_unit.core.source_code[self.in_file]
         self.dont_mutate_line = dont_mutate_line
         # total revert/comment/tweak mutants that were generated and compiled
         self.total_mutant_counts = [0, 0, 0]
diff --git a/slither/tools/mutator/utils/testing_generated_mutant.py b/slither/tools/mutator/utils/testing_generated_mutant.py
index d5725485b..2ea3314e6 100644
--- a/slither/tools/mutator/utils/testing_generated_mutant.py
+++ b/slither/tools/mutator/utils/testing_generated_mutant.py
@@ -75,8 +75,8 @@ def run_test_cmd(
 
     # If tests fail in verbose-mode, print both stdout and stderr for easier debugging
     if verbose:
-        logger.info(yellow(result.stdout.decode("utf-8")))
-        logger.info(red(result.stderr.decode("utf-8")))
+        logger.info(yellow(result.stdout.decode("utf8")))
+        logger.info(red(result.stderr.decode("utf8")))
 
     return False
 
@@ -96,12 +96,12 @@ def test_patch(  # pylint: disable=too-many-arguments
     function to verify whether each patch is caught by tests
     returns: 0 (uncaught), 1 (caught), or 2 (compilation failure)
     """
-    with open(file, "r", encoding="utf-8") as filepath:
+    with open(file, "r", encoding="utf8") as filepath:
         content = filepath.read()
     # Perform the replacement based on the index values
     replaced_content = content[: patch["start"]] + patch["new_string"] + content[patch["end"] :]
     # Write the modified content back to the file
-    with open(file, "w", encoding="utf-8") as filepath:
+    with open(file, "w", encoding="utf8") as filepath:
         filepath.write(replaced_content)
 
     if compile_generated_mutant(file, mappings):
diff --git a/slither/tools/read_storage/__main__.py b/slither/tools/read_storage/__main__.py
index 3baa5d351..23b98764c 100644
--- a/slither/tools/read_storage/__main__.py
+++ b/slither/tools/read_storage/__main__.py
@@ -169,7 +169,7 @@ def main() -> None:
         print(srs.table)
 
     if args.json:
-        with open(args.json, "w", encoding="utf-8") as file:
+        with open(args.json, "w", encoding="utf8") as file:
             slot_infos_json = srs.to_json()
             json.dump(slot_infos_json, file, indent=4)
 
diff --git a/slither/utils/function.py b/slither/utils/function.py
index 64c098bfd..ede9e470b 100644
--- a/slither/utils/function.py
+++ b/slither/utils/function.py
@@ -10,7 +10,7 @@ def get_function_id(sig: str) -> int:
         (int)
     """
     digest = keccak.new(digest_bits=256)
-    digest.update(sig.encode("utf-8"))
+    digest.update(sig.encode("utf8"))
     return int("0x" + digest.hexdigest()[:8], 16)
 
 
@@ -23,5 +23,5 @@ def get_event_id(sig: str) -> int:
         (int)
     """
     digest = keccak.new(digest_bits=256)
-    digest.update(sig.encode("utf-8"))
+    digest.update(sig.encode("utf8"))
     return int("0x" + digest.hexdigest(), 16)
diff --git a/slither/utils/output.py b/slither/utils/output.py
index 176b250e3..59bfa1872 100644
--- a/slither/utils/output.py
+++ b/slither/utils/output.py
@@ -411,7 +411,7 @@ def __init__(
         self._markdown_root = markdown_root
 
         id_txt = "".join(_convert_to_id(d) for d in info)
-        self._data["id"] = hashlib.sha3_256(id_txt.encode("utf-8")).hexdigest()
+        self._data["id"] = hashlib.sha3_256(id_txt.encode("utf8")).hexdigest()
 
         if standard_format:
             to_add = [i for i in info if not isinstance(i, str)]
diff --git a/slither/utils/standard_libraries.py b/slither/utils/standard_libraries.py
index 525771187..82defd51a 100644
--- a/slither/utils/standard_libraries.py
+++ b/slither/utils/standard_libraries.py
@@ -68,7 +68,7 @@ def is_openzeppelin(contract: "Contract") -> bool:
 
 
 def is_openzeppelin_strict(contract: "Contract") -> bool:
-    source_hash = sha1(contract.source_mapping.content.encode("utf-8")).hexdigest()
+    source_hash = sha1(contract.source_mapping.content.encode("utf8")).hexdigest()
     return source_hash in oz_hashes
 
 
diff --git a/slither/visitors/expression/constants_folding.py b/slither/visitors/expression/constants_folding.py
index ddadb77a1..65574df67 100644
--- a/slither/visitors/expression/constants_folding.py
+++ b/slither/visitors/expression/constants_folding.py
@@ -276,7 +276,7 @@ def _post_call_expression(self, expression: expressions.CallExpression) -> None:
         args = [get_val(arg) for arg in expression.arguments]
         if called.name == "keccak256(bytes)":
             digest = keccak.new(digest_bits=256)
-            digest.update(str(args[0]).encode("utf-8"))
+            digest.update(str(args[0]).encode("utf8"))
             set_val(expression, digest.digest())
         else:
             raise NotConstant

From b3a226e10ee9f1242a35290b21e20a60c3420d07 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Fri, 7 Feb 2025 14:28:23 -0500
Subject: [PATCH 12/15] bugfix Makefile

---
 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 17697385e..6c6955fa7 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ PY_MODULE := slither
 TEST_MODULE := tests
 
 ALL_PY_SRCS := $(shell find $(PY_MODULE) -name '*.py') \
-	$(shell find test -name '*.py')
+	$(shell find tests -name '*.py')
 
 # Optionally overridden by the user, if they're using a virtual environment manager.
 VENV ?= env
@@ -85,4 +85,4 @@ package: $(VENV)/pyvenv.cfg
 
 .PHONY: edit
 edit:
-	$(EDITOR) $(ALL_PY_SRCS)
\ No newline at end of file
+	$(EDITOR) $(ALL_PY_SRCS)

From 8dee964d1f4471b4ab45dc1655450c99bd3ea0e8 Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Fri, 7 Feb 2025 14:53:17 -0500
Subject: [PATCH 13/15] fix formatting

---
 slither/core/source_mapping/source_mapping.py |  4 +-
 slither/tools/documentation/__main__.py       |  8 ++-
 slither/tools/flattening/flattening.py        | 61 ++++++++++++-------
 3 files changed, 46 insertions(+), 27 deletions(-)

diff --git a/slither/core/source_mapping/source_mapping.py b/slither/core/source_mapping/source_mapping.py
index fbb7279a2..7a6cdae41 100644
--- a/slither/core/source_mapping/source_mapping.py
+++ b/slither/core/source_mapping/source_mapping.py
@@ -84,8 +84,8 @@ def content(self) -> str:
         assert self.compilation_unit
         return (
             self.compilation_unit.core.source_code[self.filename.absolute]
-                .encode("utf8")[self.start : self.end]
-                .decode("utf8")
+            .encode("utf8")[self.start : self.end]
+            .decode("utf8")
         )
 
     @property
diff --git a/slither/tools/documentation/__main__.py b/slither/tools/documentation/__main__.py
index 417e4f09a..dccdabba4 100644
--- a/slither/tools/documentation/__main__.py
+++ b/slither/tools/documentation/__main__.py
@@ -156,7 +156,9 @@ def _handle_function(
     prompt = "Create a natpsec documentation for this solidity code with only notice and dev.\n"
     srcmap = function.source_mapping
     src = function.compilation_unit.core.source_code[srcmap.filename.absolute]
-    first_char_index = len(src.encode("utf8")[:srcmap.start].decode("utf8")) # convert byte offset to char offset
+    first_char_index = len(
+        src.encode("utf8")[: srcmap.start].decode("utf8")
+    )  # convert byte offset to char offset
     prev_char = src[first_char_index - 1]
     prompt += srcmap.content
 
@@ -201,7 +203,9 @@ def _handle_function(
     if not answer_processed:
         return overwrite
 
-    create_patch(all_patches, srcmap.filename.absolute, srcmap.start, srcmap.start, "", answer_processed)
+    create_patch(
+        all_patches, srcmap.filename.absolute, srcmap.start, srcmap.start, "", answer_processed
+    )
 
     return overwrite
 
diff --git a/slither/tools/flattening/flattening.py b/slither/tools/flattening/flattening.py
index 858a83c1f..518e36717 100644
--- a/slither/tools/flattening/flattening.py
+++ b/slither/tools/flattening/flattening.py
@@ -107,8 +107,9 @@ def _get_source_code(
         :return:
         """
         src_mapping = contract.source_mapping
-        # TODO: this needs to be encoded before it gets indexed!
-        src_bytes = self._compilation_unit.core.source_code[src_mapping.filename.absolute]
+        src_bytes = self._compilation_unit.core.source_code[src_mapping.filename.absolute].encode(
+            "utf8"
+        )
 
         to_patch = []
         # interface must use external
@@ -123,8 +124,8 @@ def _get_source_code(
                         + f.parameters_src().source_mapping.length
                     )
                     attributes_end = f.returns_src().source_mapping.start
-                    attributes = src_bytes[attributes_start:attributes_end]
-                    regex = re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes.decode("utf8"))
+                    attributes = src_bytes[attributes_start:attributes_end].decode("utf8")
+                    regex = re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes)
                     if regex:
                         to_patch.append(
                             Patch(
@@ -133,7 +134,7 @@ def _get_source_code(
                             )
                         )
                     else:
-                        raise SlitherException(f"External keyword not found {f.name} {attributes.decode("utf8")}")
+                        raise SlitherException(f"External keyword not found {f.name} {attributes}")
 
                     for var in f.parameters:
                         if var.location == "calldata":
@@ -157,11 +158,11 @@ def _get_source_code(
                         + f.parameters_src().source_mapping["length"]
                     )
                     attributes_end = f.returns_src().source_mapping["start"]
-                    attributes = src_bytes[attributes_start:attributes_end]
+                    attributes = src_bytes[attributes_start:attributes_end].decode("utf8")
                     regex = (
-                        re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes.decode("utf8"))
+                        re.search(r"((\sexternal)\s+)|(\sexternal)$|(\)external)$", attributes)
                         if visibility == "external"
-                        else re.search(r"((\spublic)\s+)|(\spublic)$|(\)public)$", attributes.decode("utf8"))
+                        else re.search(r"((\spublic)\s+)|(\spublic)$|(\)public)$", attributes)
                     )
                     if regex:
                         to_patch.append(
@@ -174,7 +175,7 @@ def _get_source_code(
                         )
                     else:
                         raise SlitherException(
-                            f"{visibility} keyword not found {f.name} {attributes.decode("utf8")}"
+                            f"{visibility} keyword not found {f.name} {attributes}"
                         )
 
         if self._private_to_internal:
@@ -182,8 +183,8 @@ def _get_source_code(
                 if variable.visibility == "private":
                     attributes_start = variable.source_mapping.start
                     attributes_end = attributes_start + variable.source_mapping.length
-                    attributes = src_bytes[attributes_start:attributes_end]
-                    regex = re.search(r" private ", attributes.decode("utf8"))
+                    attributes = src_bytes[attributes_start:attributes_end].decode("utf8")
+                    regex = re.search(r" private ", attributes)
                     if regex:
                         to_patch.append(
                             Patch(
@@ -193,7 +194,7 @@ def _get_source_code(
                         )
                     else:
                         raise SlitherException(
-                            f"private keyword not found {variable.name} {attributes.decode("utf8")}"
+                            f"private keyword not found {variable.name} {attributes}"
                         )
 
         if self._remove_assert:
@@ -210,12 +211,6 @@ def _get_source_code(
 
         to_patch.sort(key=lambda x: x.index, reverse=True)
 
-        # Note: foundry and solc and everything else return srcmap offsets per-byte
-        # and it seems the rest of slither operates on bytes also
-        # it might just be the mutator and flattener that are incorrectly applying offsets directly to strings
-        # I think I just need to do the following (and similar for mutations)
-        # content = content.encode("utf8")[start:end].decode("utf8")
-
         content = src_mapping.content.encode("utf8")
         start = src_mapping.start
         for patch in to_patch:
@@ -223,15 +218,35 @@ def _get_source_code(
             index = patch.index
             index = index - start
             if patch_type == "public_to_external":
-                content = content[:index].decode("utf8") + "public" + content[index + len("external") :].decode("utf8")
+                content = (
+                    content[:index].decode("utf8")
+                    + "public"
+                    + content[index + len("external") :].decode("utf8")
+                )
             elif patch_type == "external_to_internal":
-                content = content[:index].decode("utf8") + "internal" + content[index + len("external") :].decode("utf8")
+                content = (
+                    content[:index].decode("utf8")
+                    + "internal"
+                    + content[index + len("external") :].decode("utf8")
+                )
             elif patch_type == "public_to_internal":
-                content = content[:index].decode("utf8") + "internal" + content[index + len("public") :].decode("utf8")
+                content = (
+                    content[:index].decode("utf8")
+                    + "internal"
+                    + content[index + len("public") :].decode("utf8")
+                )
             elif patch_type == "private_to_internal":
-                content = content[:index].decode("utf8") + "internal" + content[index + len("private") :].decode("utf8")
+                content = (
+                    content[:index].decode("utf8")
+                    + "internal"
+                    + content[index + len("private") :].decode("utf8")
+                )
             elif patch_type == "calldata_to_memory":
-                content = content[:index].decode("utf8") + "memory" + content[index + len("calldata") :].decode("utf8")
+                content = (
+                    content[:index].decode("utf8")
+                    + "memory"
+                    + content[index + len("calldata") :].decode("utf8")
+                )
             else:
                 assert patch_type == "line_removal"
                 content = content[:index].decode("utf8") + " // " + content[index:].decode("utf8")

From 78fe705920ae0b79277447c4065b34a867d689df Mon Sep 17 00:00:00 2001
From: bohendo <bo.henderson@trailofbits.com>
Date: Mon, 10 Feb 2025 11:41:34 -0500
Subject: [PATCH 14/15] bugfix naming_convention formatter

---
 slither/formatters/naming_convention/naming_convention.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/slither/formatters/naming_convention/naming_convention.py b/slither/formatters/naming_convention/naming_convention.py
index 8b3c40df4..56fdf86b7 100644
--- a/slither/formatters/naming_convention/naming_convention.py
+++ b/slither/formatters/naming_convention/naming_convention.py
@@ -339,7 +339,7 @@ def _is_var_declaration(slither: SlitherCompilationUnit, filename: str, start: i
     :return:
     """
     v = "var "
-    return slither.core.source_code[filename][start : start + len(v)] == v
+    return slither.core.source_code[filename].encode("utf8")[start : start + len(v)].decode("utf8") == v
 
 
 def _explore_type(  # pylint: disable=too-many-arguments,too-many-locals,too-many-branches

From 277f011a7b62e1c1f04980810a9ae3371a980d9e Mon Sep 17 00:00:00 2001
From: bohendo <8527067+bohendo@users.noreply.github.com>
Date: Mon, 10 Feb 2025 12:40:39 -0500
Subject: [PATCH 15/15] fix formatting

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 slither/formatters/naming_convention/naming_convention.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/slither/formatters/naming_convention/naming_convention.py b/slither/formatters/naming_convention/naming_convention.py
index 56fdf86b7..ebb6b7f5b 100644
--- a/slither/formatters/naming_convention/naming_convention.py
+++ b/slither/formatters/naming_convention/naming_convention.py
@@ -339,7 +339,10 @@ def _is_var_declaration(slither: SlitherCompilationUnit, filename: str, start: i
     :return:
     """
     v = "var "
-    return slither.core.source_code[filename].encode("utf8")[start : start + len(v)].decode("utf8") == v
+    return (
+        slither.core.source_code[filename].encode("utf8")[start : start + len(v)].decode("utf8")
+        == v
+    )
 
 
 def _explore_type(  # pylint: disable=too-many-arguments,too-many-locals,too-many-branches