Rollup merge of #134154 - dev-ardi:field-expr-generics, r=compiler-errors

suppress field expr with generics error message if it's a method Don't emit "field expressions may not have generic arguments" if it's a method call without `()` r? estebank Fixes #67680 Is this the best way to go? It's by far the simplest I could come up with.

Author: matthiaskrgr

compiler/rustc_errors/src/lib.rs

@@ -576,6 +576,10 @@ pub enum StashKey {
  UndeterminedMacroResolution,
  /// Used by `Parser::maybe_recover_trailing_expr`
  ExprInPat,
+ /// If in the parser we detect a field expr with turbofish generic params it's possible that
+ /// it's a method call without parens. If later on in `hir_typeck` we find out that this is
+ /// the case we suppress this message and we give a better suggestion.
+ GenericInFieldExpr,
 }
 
 fn default_track_diagnostic<R>(diag: DiagInner, f: &mut dyn FnMut(DiagInner) -> R) -> R {

compiler/rustc_hir_typeck/src/expr.rs

@@ -3076,7 +3076,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  err.help("methods are immutable and cannot be assigned to");
  }
 
- err.emit()
+ // See `StashKey::GenericInFieldExpr` for more info
+ self.dcx().try_steal_replace_and_emit_err(field.span, StashKey::GenericInFieldExpr, err)
  }
 
  fn point_at_param_definition(&self, err: &mut Diag<'_>, param: ty::ParamTy) {

compiler/rustc_parse/src/parser/expr.rs

@@ -1369,11 +1369,14 @@ impl<'a> Parser<'a> {
  ))
  } else {
  // Field access `expr.f`
+ let span = lo.to(self.prev_token.span);
  if let Some(args) = seg.args {
- self.dcx().emit_err(errors::FieldExpressionWithGeneric(args.span()));
+ // See `StashKey::GenericInFieldExpr` for more info on why we stash this.
+ self.dcx()
+ .create_err(errors::FieldExpressionWithGeneric(args.span()))
+ .stash(seg.ident.span, StashKey::GenericInFieldExpr);
  }
 
- let span = lo.to(self.prev_token.span);
  Ok(self.mk_expr(span, ExprKind::Field(self_arg, seg.ident)))
  }
  }

tests/ui/parser/bad-name.stderr

@@ -1,9 +1,3 @@
-error: field expressions cannot have generic arguments
- --> $DIR/bad-name.rs:2:12
- |
-LL | let x.y::<isize>.z foo;
- | ^^^^^^^
-
 error: expected a pattern, found an expression
  --> $DIR/bad-name.rs:2:7
  |
@@ -18,5 +12,11 @@ error: expected one of `(`, `.`, `::`, `:`, `;`, `=`, `?`, `|`, or an operator,
 LL | let x.y::<isize>.z foo;
  | ^^^ expected one of 9 possible tokens
 
+error: field expressions cannot have generic arguments
+ --> $DIR/bad-name.rs:2:12
+ |
+LL | let x.y::<isize>.z foo;
+ | ^^^^^^^
+
 error: aborting due to 3 previous errors
 

tests/ui/suggestions/method-missing-parentheses.rs

@@ -1,5 +1,4 @@
 fn main() {
  let _ = vec![].into_iter().collect::<usize>;
  //~^ ERROR attempted to take value of method `collect` on type `std::vec::IntoIter<_>`
- //~| ERROR field expressions cannot have generic arguments
 }

tests/ui/suggestions/method-missing-parentheses.stderr

@@ -1,9 +1,3 @@
-error: field expressions cannot have generic arguments
- --> $DIR/method-missing-parentheses.rs:2:41
- |
-LL | let _ = vec![].into_iter().collect::<usize>;
- | ^^^^^^^
-
 error[E0615]: attempted to take value of method `collect` on type `std::vec::IntoIter<_>`
  --> $DIR/method-missing-parentheses.rs:2:32
  |
@@ -15,6 +9,6 @@ help: use parentheses to call the method
 LL | let _ = vec![].into_iter().collect::<usize>();
  | ++
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0615`.