From 2cbf5127d58553fd6224a1ec809536bccc5b8510 Mon Sep 17 00:00:00 2001
From: Bill Wendling <morbo@google.com>
Date: Fri, 7 Apr 2023 11:35:29 -0700
Subject: [PATCH] [Clang] Improve designated inits diagnostic location

A "null" designator won't have a valid location. Try to approximate this
location as best we can in that situation.

Closes 61118
Closes 46132

Reviewed By: shafik

Differential Revision: https://reviews.llvm.org/D147673
---
 clang/lib/Sema/SemaInit.cpp                         | 11 +++++++++--
 .../test/SemaCXX/cxx2b-designated-initializers.cpp  | 21 +++++++++++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/SemaCXX/cxx2b-designated-initializers.cpp

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 5fe417f..be46191 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -2641,8 +2641,15 @@ InitListChecker::CheckDesignatedInitializer(const InitializedEntity &Entity,
           hadError = true;
         } else {
           // Typo correction didn't find anything.
-          SemaRef.Diag(D->getFieldLoc(), diag::err_field_designator_unknown)
-            << FieldName << CurrentObjectType;
+          SourceLocation Loc = D->getFieldLoc();
+
+          // The loc can be invalid with a "null" designator (i.e. an anonymous
+          // union/struct). Do our best to approximate the location.
+          if (Loc.isInvalid())
+            Loc = IList->getBeginLoc();
+
+          SemaRef.Diag(Loc, diag::err_field_designator_unknown)
+            << FieldName << CurrentObjectType << DIE->getSourceRange();
           ++Index;
           return true;
         }
diff --git a/clang/test/SemaCXX/cxx2b-designated-initializers.cpp b/clang/test/SemaCXX/cxx2b-designated-initializers.cpp
new file mode 100644
index 0000000..3cddb5d
--- /dev/null
+++ b/clang/test/SemaCXX/cxx2b-designated-initializers.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify %s
+
+namespace PR61118 {
+
+union S {
+  struct {
+    int a;
+  };
+};
+
+void f(int x, auto) {
+  const S result { // expected-error {{field designator (null) does not refer to any field in type 'const S'}}
+    .a = x
+  };
+}
+
+void g(void) {
+  f(0, 0); // expected-note {{in instantiation of function template specialization 'PR61118::f<int>' requested here}}
+}
+
+} // end namespace PR61118
-- 
2.7.4