From ec5e685c4fa52e63ea13db63afa0e22d2805409f Mon Sep 17 00:00:00 2001
From: Orion Gonzalez <ardi@ardis.dev>
Date: Wed, 11 Dec 2024 00:53:07 +0100
Subject: [PATCH] Don't emit "field expressions may not have generic arguments"
 if it's a method call without ()

---
 compiler/rustc_errors/src/lib.rs                   |  1 +
 compiler/rustc_hir_typeck/src/expr.rs              |  2 +-
 compiler/rustc_parse/src/parser/expr.rs            |  6 ++++--
 tests/ui/parser/bad-name.stderr                    | 12 ++++++------
 ...680-method-call-with-generics-without-parens.rs |  4 ++++
 ...method-call-with-generics-without-parens.stderr | 14 ++++++++++++++
 6 files changed, 30 insertions(+), 9 deletions(-)
 create mode 100644 tests/ui/parser/issue-67680-method-call-with-generics-without-parens.rs
 create mode 100644 tests/ui/parser/issue-67680-method-call-with-generics-without-parens.stderr

diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 6232c875ee81e..39b90c0b31c43 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -576,6 +576,7 @@ pub enum StashKey {
     UndeterminedMacroResolution,
     /// Used by `Parser::maybe_recover_trailing_expr`
     ExprInPat,
+    GenericInFieldExpr,
 }
 
 fn default_track_diagnostic<R>(diag: DiagInner, f: &mut dyn FnMut(DiagInner) -> R) -> R {
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 0e079b037691e..6518a9312c367 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -3055,7 +3055,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             err.help("methods are immutable and cannot be assigned to");
         }
 
-        err.emit()
+        self.dcx().try_steal_replace_and_emit_err(expr.span, StashKey::GenericInFieldExpr, err)
     }
 
     fn point_at_param_definition(&self, err: &mut Diag<'_>, param: ty::ParamTy) {
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index eeb83a85e59bb..07222482dcfb8 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1369,11 +1369,13 @@ 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()));
+                self.dcx()
+                    .create_err(errors::FieldExpressionWithGeneric(args.span()))
+                    .stash(span, StashKey::GenericInFieldExpr);
             }
 
-            let span = lo.to(self.prev_token.span);
             Ok(self.mk_expr(span, ExprKind::Field(self_arg, seg.ident)))
         }
     }
diff --git a/tests/ui/parser/bad-name.stderr b/tests/ui/parser/bad-name.stderr
index a336923f4fd89..112fdcad3369c 100644
--- a/tests/ui/parser/bad-name.stderr
+++ b/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
 
diff --git a/tests/ui/parser/issue-67680-method-call-with-generics-without-parens.rs b/tests/ui/parser/issue-67680-method-call-with-generics-without-parens.rs
new file mode 100644
index 0000000000000..9d90cdad0fa28
--- /dev/null
+++ b/tests/ui/parser/issue-67680-method-call-with-generics-without-parens.rs
@@ -0,0 +1,4 @@
+fn main() {
+    [1, 2].into_iter().collect::<Vec<i32>>;
+    //~^ ERROR attempted to take value of method
+}
diff --git a/tests/ui/parser/issue-67680-method-call-with-generics-without-parens.stderr b/tests/ui/parser/issue-67680-method-call-with-generics-without-parens.stderr
new file mode 100644
index 0000000000000..bf9c71479d545
--- /dev/null
+++ b/tests/ui/parser/issue-67680-method-call-with-generics-without-parens.stderr
@@ -0,0 +1,14 @@
+error[E0615]: attempted to take value of method `collect` on type `std::slice::Iter<'_, {integer}>`
+  --> $DIR/issue-67680-method-call-with-generics-without-parens.rs:2:24
+   |
+LL |     [1, 2].into_iter().collect::<Vec<i32>>;
+   |                        ^^^^^^^ method, not a field
+   |
+help: use parentheses to call the method
+   |
+LL |     [1, 2].into_iter().collect::<Vec<i32>>();
+   |                                           ++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0615`.