Merge pull request #87 from justinboswell/ctad

Added support for template deduction guides

Author: virtuald

cxxheaderparser/parser.py

@@ -25,6 +25,7 @@
     Concept,
     DecltypeSpecifier,
     DecoratedType,
+    DeductionGuide,
     EnumDecl,
     Enumerator,
     Field,
@@ -1868,10 +1869,9 @@ def _parse_parameters(
     _auto_return_typename = PQName([AutoSpecifier()])
 
     def _parse_trailing_return_type(
-        self, fn: typing.Union[Function, FunctionType]
-    ) -> None:
+        self, return_type: typing.Optional[DecoratedType]
+    ) -> DecoratedType:
         # entry is "->"
-        return_type = fn.return_type
         if not (
             isinstance(return_type, Type)
             and not return_type.const
@@ -1890,8 +1890,7 @@ def _parse_trailing_return_type(
 
         dtype = self._parse_cv_ptr(parsed_type)
 
-        fn.has_trailing_return = True
-        fn.return_type = dtype
+        return dtype
 
     def _parse_fn_end(self, fn: Function) -> None:
         """
@@ -1918,7 +1917,9 @@ def _parse_fn_end(self, fn: Function) -> None:
                 fn.raw_requires = self._parse_requires(rtok)
 
         if self.lex.token_if("ARROW"):
-            self._parse_trailing_return_type(fn)
+            return_type = self._parse_trailing_return_type(fn.return_type)
+            fn.has_trailing_return = True
+            fn.return_type = return_type
 
         if self.lex.token_if("{"):
             self._discard_contents("{", "}")
@@ -1966,7 +1967,9 @@ def _parse_method_end(self, method: Method) -> None:
             elif tok_value in ("&", "&&"):
                 method.ref_qualifier = tok_value
             elif tok_value == "->":
-                self._parse_trailing_return_type(method)
+                return_type = self._parse_trailing_return_type(method.return_type)
+                method.has_trailing_return = True
+                method.return_type = return_type
                 if self.lex.token_if("{"):
                     self._discard_contents("{", "}")
                     method.has_body = True
@@ -2000,6 +2003,7 @@ def _parse_function(
         is_friend: bool,
         is_typedef: bool,
         msvc_convention: typing.Optional[LexToken],
+        is_guide: bool = False,
     ) -> bool:
         """
         Assumes the caller has already consumed the return type and name, this consumes the
@@ -2076,7 +2080,21 @@ def _parse_function(
                 self.visitor.on_method_impl(state, method)
 
             return method.has_body or method.has_trailing_return
-
+        elif is_guide:
+            assert isinstance(state, (ExternBlockState, NamespaceBlockState))
+            if not self.lex.token_if("ARROW"):
+                raise self._parse_error(None, expected="Trailing return type")
+            return_type = self._parse_trailing_return_type(
+                Type(PQName([AutoSpecifier()]))
+            )
+            guide = DeductionGuide(
+                return_type,
+                name=pqname,
+                parameters=params,
+                doxygen=doxygen,
+            )
+            self.visitor.on_deduction_guide(state, guide)
+            return False
         else:
             assert return_type is not None
             fn = Function(
@@ -2210,7 +2228,9 @@ def _parse_cv_ptr_or_fn(
                 assert not isinstance(dtype, FunctionType)
                 dtype = dtype_fn = FunctionType(dtype, fn_params, vararg)
                 if self.lex.token_if("ARROW"):
-                    self._parse_trailing_return_type(dtype_fn)
+                    return_type = self._parse_trailing_return_type(dtype_fn.return_type)
+                    dtype_fn.has_trailing_return = True
+                    dtype_fn.return_type = return_type
 
             else:
                 msvc_convention = None
@@ -2391,6 +2411,7 @@ def _parse_decl(
         destructor = False
         op = None
         msvc_convention = None
+        is_guide = False
 
         # If we have a leading (, that's either an obnoxious grouping
         # paren or it's a constructor
@@ -2441,8 +2462,15 @@ def _parse_decl(
                 # grouping paren like "void (name(int x));"
                 toks = self._consume_balanced_tokens(tok)
 
-                # .. not sure what it's grouping, so put it back?
-                self.lex.return_tokens(toks[1:-1])
+                # check to see if the next token is an arrow, and thus a trailing return
+                if self.lex.token_peek_if("ARROW"):
+                    self.lex.return_tokens(toks)
+                    # the leading name of the class/ctor has been parsed as a type before the parens
+                    pqname = parsed_type.typename
+                    is_guide = True
+                else:
+                    # .. not sure what it's grouping, so put it back?
+                    self.lex.return_tokens(toks[1:-1])
 
         if dtype:
             msvc_convention = self.lex.token_if_val(*self._msvc_conventions)
@@ -2473,6 +2501,7 @@ def _parse_decl(
                 is_friend,
                 is_typedef,
                 msvc_convention,
+                is_guide,
             )
         elif msvc_convention:
             raise self._parse_error(msvc_convention)

cxxheaderparser/simple.py

@@ -35,6 +35,7 @@
 from .types import (
     ClassDecl,
     Concept,
+    DeductionGuide,
     EnumDecl,
     Field,
     ForwardDecl,
@@ -123,6 +124,9 @@ class NamespaceScope:
     #: Child namespaces
     namespaces: typing.Dict[str, "NamespaceScope"] = field(default_factory=dict)
 
+    #: Deduction guides
+    deduction_guides: typing.List[DeductionGuide] = field(default_factory=list)
+
 
 Block = typing.Union[ClassScope, NamespaceScope]
 
@@ -317,6 +321,11 @@ def on_class_friend(self, state: SClassBlockState, friend: FriendDecl) -> None:
     def on_class_end(self, state: SClassBlockState) -> None:
         pass
 
+    def on_deduction_guide(
+        self, state: SNonClassBlockState, guide: DeductionGuide
+    ) -> None:
+        state.user_data.deduction_guides.append(guide)
+
 
 def parse_string(
     content: str,

cxxheaderparser/types.py

@@ -896,3 +896,21 @@ class UsingAlias:
 
     #: Documentation if present
     doxygen: typing.Optional[str] = None
+
+
+@dataclass
+class DeductionGuide:
+    """
+    .. code-block:: c++
+
+    template <class T>
+    MyClass(T) -> MyClass(int);
+    """
+
+    #: Only constructors and destructors don't have a return type
+    result_type: typing.Optional[DecoratedType]
+
+    name: PQName
+    parameters: typing.List[Parameter]
+
+    doxygen: typing.Optional[str] = None

cxxheaderparser/visitor.py

@@ -9,6 +9,7 @@
 
 from .types import (
     Concept,
+    DeductionGuide,
     EnumDecl,
     Field,
     ForwardDecl,
@@ -236,6 +237,13 @@ def on_class_end(self, state: ClassBlockState) -> None:
         ``on_variable`` for each instance declared.
         """
 
+    def on_deduction_guide(
+        self, state: NonClassBlockState, guide: DeductionGuide
+    ) -> None:
+        """
+        Called when a deduction guide is encountered
+        """
+
 
 class NullVisitor:
     """
@@ -318,5 +326,10 @@ def on_class_method(self, state: ClassBlockState, method: Method) -> None:
     def on_class_end(self, state: ClassBlockState) -> None:
         return None
 
+    def on_deduction_guide(
+        self, state: NonClassBlockState, guide: DeductionGuide
+    ) -> None:
+        return None
+
 
 null_visitor = NullVisitor()

tests/test_template.py

@@ -5,6 +5,7 @@
     BaseClass,
     ClassDecl,
     DecltypeSpecifier,
+    DeductionGuide,
     Field,
     ForwardDecl,
     Function,
@@ -2163,3 +2164,86 @@ def test_member_class_template_specialization() -> None:
             ]
         )
     )
+
+
+def test_template_deduction_guide() -> None:
+    content = """
+      template <class CharT, class Traits = std::char_traits<CharT>>
+      Error(std::basic_string_view<CharT, Traits>) -> Error<std::string>;
+    """
+    data = parse_string(content, cleandoc=True)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            deduction_guides=[
+                DeductionGuide(
+                    result_type=Type(
+                        typename=PQName(
+                            segments=[
+                                NameSpecifier(
+                                    name="Error",
+                                    specialization=TemplateSpecialization(
+                                        args=[
+                                            TemplateArgument(
+                                                arg=Type(
+                                                    typename=PQName(
+                                                        segments=[
+                                                            NameSpecifier(name="std"),
+                                                            NameSpecifier(
+                                                                name="string"
+                                                            ),
+                                                        ]
+                                                    )
+                                                )
+                                            )
+                                        ]
+                                    ),
+                                )
+                            ]
+                        )
+                    ),
+                    name=PQName(segments=[NameSpecifier(name="Error")]),
+                    parameters=[
+                        Parameter(
+                            type=Type(
+                                typename=PQName(
+                                    segments=[
+                                        NameSpecifier(name="std"),
+                                        NameSpecifier(
+                                            name="basic_string_view",
+                                            specialization=TemplateSpecialization(
+                                                args=[
+                                                    TemplateArgument(
+                                                        arg=Type(
+                                                            typename=PQName(
+                                                                segments=[
+                                                                    NameSpecifier(
+                                                                        name="CharT"
+                                                                    )
+                                                                ]
+                                                            )
+                                                        )
+                                                    ),
+                                                    TemplateArgument(
+                                                        arg=Type(
+                                                            typename=PQName(
+                                                                segments=[
+                                                                    NameSpecifier(
+                                                                        name="Traits"
+                                                                    )
+                                                                ]
+                                                            )
+                                                        )
+                                                    ),
+                                                ]
+                                            ),
+                                        ),
+                                    ]
+                                )
+                            )
+                        )
+                    ],
+                )
+            ]
+        )
+    )