1 files changed, 36 insertions, 25 deletions

diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index 8ba811715..8d0f168e0 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -1,4 +1,8 @@
-use crate::errors::{WhereClauseBeforeTupleStructBody, WhereClauseBeforeTupleStructBodySugg};
+use crate::errors::{
+    MultipleWhereClauses, UnexpectedDefaultValueForLifetimeInGenericParameters,
+    UnexpectedSelfInGenericParameters, WhereClauseBeforeTupleStructBody,
+    WhereClauseBeforeTupleStructBodySugg,
+};
 
 use super::{ForceCollect, Parser, TrailingToken};
 
@@ -10,10 +14,11 @@ use rustc_ast::{
 use rustc_errors::{Applicability, PResult};
 use rustc_span::symbol::{kw, Ident};
 use rustc_span::Span;
+use thin_vec::ThinVec;
 
 enum PredicateOrStructBody {
     Predicate(ast::WherePredicate),
-    StructBody(Vec<ast::FieldDef>),
+    StructBody(ThinVec<ast::FieldDef>),
 }
 
 impl<'a> Parser<'a> {
@@ -117,8 +122,8 @@ impl<'a> Parser<'a> {
 
     /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
     /// a trailing comma and erroneous trailing attributes.
-    pub(super) fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
-        let mut params = Vec::new();
+    pub(super) fn parse_generic_params(&mut self) -> PResult<'a, ThinVec<ast::GenericParam>> {
+        let mut params = ThinVec::new();
         let mut done = false;
         while !done {
             let attrs = self.parse_outer_attributes()?;
@@ -127,12 +132,9 @@ impl<'a> Parser<'a> {
                     if this.eat_keyword_noexpect(kw::SelfUpper) {
                         // `Self` as a generic param is invalid. Here we emit the diagnostic and continue parsing
                         // as if `Self` never existed.
-                        this.struct_span_err(
-                            this.prev_token.span,
-                            "unexpected keyword `Self` in generic parameters",
-                        )
-                        .note("you cannot use `Self` as a generic parameter because it is reserved for associated items")
-                        .emit();
+                        this.sess.emit_err(UnexpectedSelfInGenericParameters {
+                            span: this.prev_token.span,
+                        });
 
                         this.eat(&token::Comma);
                     }
@@ -145,6 +147,20 @@ impl<'a> Parser<'a> {
                         } else {
                             (None, Vec::new())
                         };
+
+                        if this.check_noexpect(&token::Eq)
+                            && this.look_ahead(1, |t| t.is_lifetime())
+                        {
+                            let lo = this.token.span;
+                            // Parse `= 'lifetime`.
+                            this.bump(); // `=`
+                            this.bump(); // `'lifetime`
+                            let span = lo.to(this.prev_token.span);
+                            this.sess.emit_err(
+                                UnexpectedDefaultValueForLifetimeInGenericParameters { span },
+                            );
+                        }
+
                         Some(ast::GenericParam {
                             ident: lifetime.ident,
                             id: lifetime.id,
@@ -236,13 +252,13 @@ impl<'a> Parser<'a> {
             self.expect_gt()?;
             (params, span_lo.to(self.prev_token.span))
         } else {
-            (vec![], self.prev_token.span.shrink_to_hi())
+            (ThinVec::new(), self.prev_token.span.shrink_to_hi())
         };
         Ok(ast::Generics {
             params,
             where_clause: WhereClause {
                 has_where_token: false,
-                predicates: Vec::new(),
+                predicates: ThinVec::new(),
                 span: self.prev_token.span.shrink_to_hi(),
             },
             span,
@@ -262,17 +278,17 @@ impl<'a> Parser<'a> {
         &mut self,
         struct_name: Ident,
         body_insertion_point: Span,
-    ) -> PResult<'a, (WhereClause, Option<Vec<ast::FieldDef>>)> {
+    ) -> PResult<'a, (WhereClause, Option<ThinVec<ast::FieldDef>>)> {
         self.parse_where_clause_common(Some((struct_name, body_insertion_point)))
     }
 
     fn parse_where_clause_common(
         &mut self,
         struct_: Option<(Ident, Span)>,
-    ) -> PResult<'a, (WhereClause, Option<Vec<ast::FieldDef>>)> {
+    ) -> PResult<'a, (WhereClause, Option<ThinVec<ast::FieldDef>>)> {
         let mut where_clause = WhereClause {
             has_where_token: false,
-            predicates: Vec::new(),
+            predicates: ThinVec::new(),
             span: self.prev_token.span.shrink_to_hi(),
         };
         let mut tuple_struct_body = None;
@@ -329,16 +345,11 @@ impl<'a> Parser<'a> {
             let ate_comma = self.eat(&token::Comma);
 
             if self.eat_keyword_noexpect(kw::Where) {
-                let msg = "cannot define duplicate `where` clauses on an item";
-                let mut err = self.struct_span_err(self.token.span, msg);
-                err.span_label(pred_lo, "previous `where` clause starts here");
-                err.span_suggestion_verbose(
-                    prev_token.shrink_to_hi().to(self.prev_token.span),
-                    "consider joining the two `where` clauses into one",
-                    ",",
-                    Applicability::MaybeIncorrect,
-                );
-                err.emit();
+                self.sess.emit_err(MultipleWhereClauses {
+                    span: self.token.span,
+                    previous: pred_lo,
+                    between: prev_token.shrink_to_hi().to(self.prev_token.span),
+                });
             } else if !ate_comma {
                 break;
             }