[llvm-branch-commits] [clang] cb79aae - [clang] Backport: allow canonicalizing assumed template names

[Douglas Yung via llvm-branch-commits]

Author: Matheus Izvekov
Date: 2026-02-28T09:26:11Z
New Revision: cb79aaed35b08a38846c5a09448870c673a88b43

URL: https://github.com/llvm/llvm-project/commit/cb79aaed35b08a38846c5a09448870c673a88b43
DIFF: https://github.com/llvm/llvm-project/commit/cb79aaed35b08a38846c5a09448870c673a88b43.diff

LOG: [clang] Backport: allow canonicalizing assumed template names

Assumed template names are part of error recovery and encode just a
declaration name, making them always canonical. This patch allows
them to be canonicalized, which is trivial.

Backport from #183222

Fixes #183075

Added: 
    clang/test/SemaTemplate/GH183075.cpp

Modified: 
    clang/lib/AST/ASTContext.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index f52470a4d7458..100e37c131ef2 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -7244,9 +7244,12 @@ TemplateName ASTContext::getCanonicalTemplateName(TemplateName Name,
     return TemplateName(cast<TemplateDecl>(Template->getCanonicalDecl()));
   }
 
-  case TemplateName::OverloadedTemplate:
   case TemplateName::AssumedTemplate:
-    llvm_unreachable("cannot canonicalize unresolved template");
+    // An assumed template is just a name, so it is already canonical.
+    return Name;
+
+  case TemplateName::OverloadedTemplate:
+    llvm_unreachable("cannot canonicalize overloaded template");
 
   case TemplateName::DependentTemplate: {
     DependentTemplateName *DTN = Name.getAsDependentTemplateName();

diff  --git a/clang/test/SemaTemplate/GH183075.cpp b/clang/test/SemaTemplate/GH183075.cpp
new file mode 100644
index 0000000000000..a9aa7d7a2157a
--- /dev/null
+++ b/clang/test/SemaTemplate/GH183075.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -verify %s
+
+int bar; // #bar
+
+int foo()
+{
+  // FIXME: Bad error recovery.
+  (void)(baz<> + baz<>);
+  // expected-error at -1 2{{use of undeclared identifier 'baz'; did you mean 'bar'?}}
+  // expected-note@#bar 2{{'bar' declared here}}
+  // expected-error at -3 2{{'bar' is expected to be a non-type template, but instantiated to a class template}}
+  // expected-note@#bar 2{{class template declared here}}
+}