Rollup merge of #67744 - Centril:reduce-diversity, r=petrochenkov

parser: reduce diversity in error handling mechanisms

Instead of having e.g. `span_err`, `fatal`, etc., we prefer to move towards uniformly using `struct_span_err` thus making it harder to emit fatal and/or unstructured diagnostics.

This PR also de-fatalizes some diagnostics.

r? @estebank

Author: Centril

src/librustc_expand/mbe/macro_parser.rs

@@ -890,12 +890,12 @@ fn parse_nt_inner<'a>(p: &mut Parser<'a>, sp: Span, name: Symbol) -> PResult<'a,
     Ok(match name {
         sym::item => match p.parse_item()? {
             Some(i) => token::NtItem(i),
-            None => return Err(p.fatal("expected an item keyword")),
+            None => return Err(p.struct_span_err(p.token.span, "expected an item keyword")),
         },
         sym::block => token::NtBlock(p.parse_block()?),
         sym::stmt => match p.parse_stmt()? {
             Some(s) => token::NtStmt(s),
-            None => return Err(p.fatal("expected a statement")),
+            None => return Err(p.struct_span_err(p.token.span, "expected a statement")),
         },
         sym::pat => token::NtPat(p.parse_pat(None)?),
         sym::expr => token::NtExpr(p.parse_expr()?),
@@ -909,7 +909,8 @@ fn parse_nt_inner<'a>(p: &mut Parser<'a>, sp: Span, name: Symbol) -> PResult<'a,
                 token::NtIdent(Ident::new(name, span), is_raw)
             } else {
                 let token_str = pprust::token_to_string(&p.token);
-                return Err(p.fatal(&format!("expected ident, found {}", &token_str)));
+                let msg = &format!("expected ident, found {}", &token_str);
+                return Err(p.struct_span_err(p.token.span, msg));
             }
         }
         sym::path => token::NtPath(p.parse_path(PathStyle::Type)?),
@@ -920,7 +921,8 @@ fn parse_nt_inner<'a>(p: &mut Parser<'a>, sp: Span, name: Symbol) -> PResult<'a,
                 token::NtLifetime(p.expect_lifetime().ident)
             } else {
                 let token_str = pprust::token_to_string(&p.token);
-                return Err(p.fatal(&format!("expected a lifetime, found `{}`", &token_str)));
+                let msg = &format!("expected a lifetime, found `{}`", &token_str);
+                return Err(p.struct_span_err(p.token.span, msg));
             }
         }
         // this is not supposed to happen, since it has been checked

src/librustc_parse/parser/attr.rs

@@ -46,7 +46,8 @@ impl<'a> Parser<'a> {
                 token::DocComment(s) => {
                     let attr = self.mk_doc_comment(s);
                     if attr.style != ast::AttrStyle::Outer {
-                        let mut err = self.fatal("expected outer doc comment");
+                        let span = self.token.span;
+                        let mut err = self.struct_span_err(span, "expected outer doc comment");
                         err.note(
                             "inner doc comments like this (starting with \
                                   `//!` or `/*!`) can only appear before items",
@@ -133,7 +134,7 @@ impl<'a> Parser<'a> {
                             "previous outer attribute"
                         };
 
-                        let mut diagnostic = self.diagnostic().struct_span_err(attr_sp, reason);
+                        let mut diagnostic = self.struct_span_err(attr_sp, reason);
 
                         if let Some(prev_attr_sp) = prev_attr_sp {
                             diagnostic
@@ -156,7 +157,8 @@ impl<'a> Parser<'a> {
             }
             _ => {
                 let token_str = pprust::token_to_string(&self.token);
-                return Err(self.fatal(&format!("expected `#`, found `{}`", token_str)));
+                let msg = &format!("expected `#`, found `{}`", token_str);
+                return Err(self.struct_span_err(self.token.span, msg));
             }
         };
 
@@ -231,8 +233,7 @@ impl<'a> Parser<'a> {
 
         if !lit.kind.is_unsuffixed() {
             let msg = "suffixed literals are not allowed in attributes";
-            self.diagnostic()
-                .struct_span_err(lit.span, msg)
+            self.struct_span_err(lit.span, msg)
                 .help(
                     "instead of using a suffixed literal \
                                     (1u8, 1.0f32, etc.), use an unsuffixed version \
@@ -332,6 +333,6 @@ impl<'a> Parser<'a> {
 
         let found = pprust::token_to_string(&self.token);
         let msg = format!("expected unsuffixed literal or identifier, found `{}`", found);
-        Err(self.diagnostic().struct_span_err(self.token.span, &msg))
+        Err(self.struct_span_err(self.token.span, &msg))
     }
 }

src/librustc_parse/parser/diagnostics.rs

@@ -157,14 +157,6 @@ crate enum ConsumeClosingDelim {
 }
 
 impl<'a> Parser<'a> {
-    pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
-        self.span_fatal(self.token.span, m)
-    }
-
-    crate fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_fatal(sp, m)
-    }
-
     pub(super) fn span_fatal_err<S: Into<MultiSpan>>(
         &self,
         sp: S,
@@ -173,14 +165,6 @@ impl<'a> Parser<'a> {
         err.span_err(sp, self.diagnostic())
     }
 
-    pub(super) fn bug(&self, m: &str) -> ! {
-        self.sess.span_diagnostic.span_bug(self.token.span, m)
-    }
-
-    pub(super) fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
-        self.sess.span_diagnostic.span_err(sp, m)
-    }
-
     pub fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
         self.sess.span_diagnostic.struct_span_err(sp, m)
     }
@@ -298,7 +282,7 @@ impl<'a> Parser<'a> {
             )
         };
         self.last_unexpected_token_span = Some(self.token.span);
-        let mut err = self.fatal(&msg_exp);
+        let mut err = self.struct_span_err(self.token.span, &msg_exp);
         let sp = if self.token == token::Eof {
             // This is EOF; don't want to point at the following char, but rather the last token.
             self.prev_span
@@ -502,18 +486,17 @@ impl<'a> Parser<'a> {
             let span = lo.until(self.token.span);
 
             let total_num_of_gt = number_of_gt + number_of_shr * 2;
-            self.diagnostic()
-                .struct_span_err(
-                    span,
-                    &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
-                )
-                .span_suggestion(
-                    span,
-                    &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
-                    String::new(),
-                    Applicability::MachineApplicable,
-                )
-                .emit();
+            self.struct_span_err(
+                span,
+                &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
+            )
+            .span_suggestion(
+                span,
+                &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
+                String::new(),
+                Applicability::MachineApplicable,
+            )
+            .emit();
         }
     }
 
@@ -762,8 +745,7 @@ impl<'a> Parser<'a> {
         path.span = ty_span.to(self.prev_span);
 
         let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
-        self.diagnostic()
-            .struct_span_err(path.span, "missing angle brackets in associated item path")
+        self.struct_span_err(path.span, "missing angle brackets in associated item path")
             .span_suggestion(
                 // This is a best-effort recovery.
                 path.span,
@@ -1271,7 +1253,8 @@ impl<'a> Parser<'a> {
 
     pub(super) fn expected_semi_or_open_brace<T>(&mut self) -> PResult<'a, T> {
         let token_str = super::token_descr(&self.token);
-        let mut err = self.fatal(&format!("expected `;` or `{{`, found {}", token_str));
+        let msg = &format!("expected `;` or `{{`, found {}", token_str);
+        let mut err = self.struct_span_err(self.token.span, msg);
         err.span_label(self.token.span, "expected `;` or `{`");
         Err(err)
     }

src/librustc_parse/parser/expr.rs

@@ -283,7 +283,7 @@ impl<'a> Parser<'a> {
                     self.mk_expr(span, aopexpr, AttrVec::new())
                 }
                 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
-                    self.bug("AssocOp should have been handled by special case")
+                    self.span_bug(span, "AssocOp should have been handled by special case")
                 }
             };
 
@@ -822,7 +822,11 @@ impl<'a> Parser<'a> {
         } else {
             // Field access `expr.f`
             if let Some(args) = segment.args {
-                self.span_err(args.span(), "field expressions may not have generic arguments");
+                self.struct_span_err(
+                    args.span(),
+                    "field expressions may not have generic arguments",
+                )
+                .emit();
             }
 
             let span = lo.to(self.prev_span);
@@ -1133,7 +1137,7 @@ impl<'a> Parser<'a> {
     pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
         self.parse_opt_lit().ok_or_else(|| {
             let msg = format!("unexpected token: {}", super::token_descr(&self.token));
-            self.span_fatal(self.token.span, &msg)
+            self.struct_span_err(self.token.span, &msg)
         })
     }
 
@@ -1446,9 +1450,7 @@ impl<'a> Parser<'a> {
         self.struct_span_err(sp, "missing condition for `if` expression")
             .span_label(sp, "expected if condition here")
             .emit();
-        let expr = self.mk_expr_err(span);
-        let stmt = self.mk_stmt(span, ast::StmtKind::Expr(expr));
-        self.mk_block(vec![stmt], BlockCheckMode::Default, span)
+        self.mk_block_err(span)
     }
 
     /// Parses the condition of a `if` or `while` expression.
@@ -1915,8 +1917,7 @@ impl<'a> Parser<'a> {
             return;
         }
 
-        self.diagnostic()
-            .struct_span_err(self.token.span, "expected `:`, found `=`")
+        self.struct_span_err(self.token.span, "expected `:`, found `=`")
             .span_suggestion(
                 field_name.span.shrink_to_hi().to(self.token.span),
                 "replace equals symbol with a colon",

src/librustc_parse/parser/item.rs

@@ -306,8 +306,7 @@ impl<'a> Parser<'a> {
                 // possible public struct definition where `struct` was forgotten
                 let ident = self.parse_ident().unwrap();
                 let msg = format!("add `struct` here to parse `{}` as a public struct", ident);
-                let mut err =
-                    self.diagnostic().struct_span_err(sp, "missing `struct` for struct definition");
+                let mut err = self.struct_span_err(sp, "missing `struct` for struct definition");
                 err.span_suggestion_short(
                     sp,
                     &msg,
@@ -335,7 +334,7 @@ impl<'a> Parser<'a> {
                 };
 
                 let msg = format!("missing `{}` for {} definition", kw, kw_name);
-                let mut err = self.diagnostic().struct_span_err(sp, &msg);
+                let mut err = self.struct_span_err(sp, &msg);
                 if !ambiguous {
                     self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
                     let suggestion =
@@ -375,7 +374,7 @@ impl<'a> Parser<'a> {
                     ("fn` or `struct", "function or struct", true)
                 };
                 let msg = format!("missing `{}` for {} definition", kw, kw_name);
-                let mut err = self.diagnostic().struct_span_err(sp, &msg);
+                let mut err = self.struct_span_err(sp, &msg);
                 if !ambiguous {
                     err.span_suggestion_short(
                         sp,
@@ -446,9 +445,7 @@ impl<'a> Parser<'a> {
         // FAILURE TO PARSE ITEM
         match visibility.node {
             VisibilityKind::Inherited => {}
-            _ => {
-                return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
-            }
+            _ => return Err(self.struct_span_err(self.prev_span, "unmatched visibility `pub`")),
         }
 
         if !attributes_allowed && !attrs.is_empty() {
@@ -466,7 +463,7 @@ impl<'a> Parser<'a> {
             _ => "expected item after attributes",
         };
 
-        let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
+        let mut err = self.struct_span_err(self.prev_span, message);
         if attrs.last().unwrap().is_doc_comment() {
             err.span_label(self.prev_span, "this doc comment doesn't document anything");
         }
@@ -536,7 +533,6 @@ impl<'a> Parser<'a> {
         //        ^^ `sp` below will point to this
         let sp = prev_span.between(self.prev_span);
         let mut err = self
-            .diagnostic()
             .struct_span_err(sp, &format!("{} for {}-item declaration", expected_kinds, item_type));
         err.span_label(sp, expected_kinds);
         err
@@ -619,7 +615,7 @@ impl<'a> Parser<'a> {
                     // This notably includes paths passed through `ty` macro fragments (#46438).
                     TyKind::Path(None, path) => path,
                     _ => {
-                        self.span_err(ty_first.span, "expected a trait, found type");
+                        self.struct_span_err(ty_first.span, "expected a trait, found type").emit();
                         err_path(ty_first.span)
                     }
                 };
@@ -1349,10 +1345,11 @@ impl<'a> Parser<'a> {
             body
         } else {
             let token_str = super::token_descr(&self.token);
-            let mut err = self.fatal(&format!(
+            let msg = &format!(
                 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
                 token_str
-            ));
+            );
+            let mut err = self.struct_span_err(self.token.span, msg);
             err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
             return Err(err);
         };
@@ -1375,8 +1372,8 @@ impl<'a> Parser<'a> {
             VariantData::Struct(fields, recovered)
         } else {
             let token_str = super::token_descr(&self.token);
-            let mut err = self
-                .fatal(&format!("expected `where` or `{{` after union name, found {}", token_str));
+            let msg = &format!("expected `where` or `{{` after union name, found {}", token_str);
+            let mut err = self.struct_span_err(self.token.span, msg);
             err.span_label(self.token.span, "expected `where` or `{` after union name");
             return Err(err);
         };
@@ -1412,10 +1409,8 @@ impl<'a> Parser<'a> {
             self.eat(&token::CloseDelim(token::Brace));
         } else {
             let token_str = super::token_descr(&self.token);
-            let mut err = self.fatal(&format!(
-                "expected `where`, or `{{` after struct name, found {}",
-                token_str
-            ));
+            let msg = &format!("expected `where`, or `{{` after struct name, found {}", token_str);
+            let mut err = self.struct_span_err(self.token.span, msg);
             err.span_label(self.token.span, "expected `where`, or `{` after struct name");
             return Err(err);
         }
@@ -1603,9 +1598,8 @@ impl<'a> Parser<'a> {
             VisibilityKind::Inherited => {}
             _ => {
                 let mut err = if self.token.is_keyword(sym::macro_rules) {
-                    let mut err = self
-                        .diagnostic()
-                        .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
+                    let mut err =
+                        self.struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
                     err.span_suggestion(
                         sp,
                         "try exporting the macro",
@@ -1614,9 +1608,8 @@ impl<'a> Parser<'a> {
                     );
                     err
                 } else {
-                    let mut err = self
-                        .diagnostic()
-                        .struct_span_err(sp, "can't qualify macro invocation with `pub`");
+                    let mut err =
+                        self.struct_span_err(sp, "can't qualify macro invocation with `pub`");
                     err.help("try adjusting the macro to put `pub` inside the invocation");
                     err
                 };

src/librustc_parse/parser/mod.rs

@@ -884,7 +884,8 @@ impl<'a> Parser<'a> {
     pub fn bump(&mut self) {
         if self.prev_token_kind == PrevTokenKind::Eof {
             // Bumping after EOF is a bad sign, usually an infinite loop.
-            self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
+            let msg = "attempted to bump the parser past EOF (may be stuck in a loop)";
+            self.span_bug(self.token.span, msg);
         }
 
         self.prev_span = self.meta_var_span.take().unwrap_or(self.token.span);
@@ -1056,8 +1057,7 @@ impl<'a> Parser<'a> {
                     _ => unreachable!(),
                 };
                 let span = self.prev_span.to(self.token.span);
-                self.diagnostic()
-                    .struct_span_fatal(span, &format!("unknown macro variable `{}`", name))
+                self.struct_span_err(span, &format!("unknown macro variable `{}`", name))
                     .span_label(span, "unknown macro variable")
                     .emit();
                 self.bump();