From ec25d6db53768a4bb68f621be3584941ac3fe416 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Mon, 26 Feb 2024 17:22:24 +1100
Subject: [PATCH] Don't cancel stashed `TraitMissingMethod` errors.

This gives one extra error message on two tests, but is necessary to fix
bigger problems caused by the cancellation of stashed errors.

(Note: why not just avoid stashing altogether? Because that resulted in
additional output changes.)
---
 compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs | 11 ++++-------
 tests/ui/resolve/issue-111312.rs               |  4 +++-
 tests/ui/resolve/issue-111312.stderr           | 16 ++++++++++++++--
 tests/ui/resolve/issue-111727.rs               |  4 +++-
 tests/ui/resolve/issue-111727.stderr           | 16 ++++++++++++++--
 5 files changed, 38 insertions(+), 13 deletions(-)

diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index a5892dea1a5..1e6467deb01 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -879,17 +879,14 @@ pub fn resolve_ty_and_res_fully_qualified_call(
                     );
                 }
 
-                // emit or cancel the diagnostic for bare traits
+                // Emit the diagnostic for bare traits. (We used to cancel for slightly better
+                // error messages, but cancelling stashed diagnostics is no longer allowed because
+                // it causes problems when tracking whether errors have actually occurred.)
                 if span.edition().at_least_rust_2021()
                     && let Some(diag) =
                         self.dcx().steal_diagnostic(qself.span, StashKey::TraitMissingMethod)
                 {
-                    if trait_missing_method {
-                        // cancel the diag for bare traits when meeting `MyTrait::missing_method`
-                        diag.cancel();
-                    } else {
-                        diag.emit();
-                    }
+                    diag.emit();
                 }
 
                 if item_name.name != kw::Empty {
diff --git a/tests/ui/resolve/issue-111312.rs b/tests/ui/resolve/issue-111312.rs
index 68fc8573dde..79c6f67dadd 100644
--- a/tests/ui/resolve/issue-111312.rs
+++ b/tests/ui/resolve/issue-111312.rs
@@ -7,5 +7,7 @@ fn has() {}
 trait HasNot {}
 
 fn main() {
-    HasNot::has(); //~ ERROR
+    HasNot::has();
+    //~^ ERROR trait objects must include the `dyn` keyword
+    //~| ERROR no function or associated item named `has` found for trait `HasNot`
 }
diff --git a/tests/ui/resolve/issue-111312.stderr b/tests/ui/resolve/issue-111312.stderr
index 7e7ef22ae61..431802ead30 100644
--- a/tests/ui/resolve/issue-111312.stderr
+++ b/tests/ui/resolve/issue-111312.stderr
@@ -1,3 +1,14 @@
+error[E0782]: trait objects must include the `dyn` keyword
+  --> $DIR/issue-111312.rs:10:5
+   |
+LL |     HasNot::has();
+   |     ^^^^^^
+   |
+help: add `dyn` keyword before this trait
+   |
+LL |     <dyn HasNot>::has();
+   |     ++++       +
+
 error[E0599]: no function or associated item named `has` found for trait `HasNot`
   --> $DIR/issue-111312.rs:10:13
    |
@@ -10,6 +21,7 @@ note: `Has` defines an item `has`
 LL | trait Has {
    | ^^^^^^^^^
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0599`.
+Some errors have detailed explanations: E0599, E0782.
+For more information about an error, try `rustc --explain E0599`.
diff --git a/tests/ui/resolve/issue-111727.rs b/tests/ui/resolve/issue-111727.rs
index 740037fe434..fcab924b809 100644
--- a/tests/ui/resolve/issue-111727.rs
+++ b/tests/ui/resolve/issue-111727.rs
@@ -1,5 +1,7 @@
 //@ edition: 2021
 
 fn main() {
-    std::any::Any::create(); //~ ERROR
+    std::any::Any::create();
+    //~^ ERROR trait objects must include the `dyn` keyword
+    //~| ERROR no function or associated item named `create` found for trait `Any`
 }
diff --git a/tests/ui/resolve/issue-111727.stderr b/tests/ui/resolve/issue-111727.stderr
index b58168d0e75..1ef5a1a1d5e 100644
--- a/tests/ui/resolve/issue-111727.stderr
+++ b/tests/ui/resolve/issue-111727.stderr
@@ -1,9 +1,21 @@
+error[E0782]: trait objects must include the `dyn` keyword
+  --> $DIR/issue-111727.rs:4:5
+   |
+LL |     std::any::Any::create();
+   |     ^^^^^^^^^^^^^
+   |
+help: add `dyn` keyword before this trait
+   |
+LL |     <dyn std::any::Any>::create();
+   |     ++++              +
+
 error[E0599]: no function or associated item named `create` found for trait `Any`
   --> $DIR/issue-111727.rs:4:20
    |
 LL |     std::any::Any::create();
    |                    ^^^^^^ function or associated item not found in `Any`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0599`.
+Some errors have detailed explanations: E0599, E0782.
+For more information about an error, try `rustc --explain E0599`.