[clang] [clang][bytecode] Fix "declared here" location of ... (PR #209696)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr updated https://github.com/llvm/llvm-project/pull/209696

>From e5968ce494baf35e1e8931117a8ed91d09c3a290 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Wed, 15 Jul 2026 09:54:26 +0200
Subject: [PATCH] [clang][bytecode] Fix "declared here" location of ...

... "read outside its lifetime" diagnostics.

We should be pointing to the first decl.
---
 clang/lib/AST/ByteCode/Interp.cpp | 5 ++---
 clang/test/AST/ByteCode/cxx11.cpp | 7 +++++++
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index 58bbf4aaf5f89..f4a5ddc99d95d 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -762,11 +762,10 @@ bool DiagnoseUninitialized(InterpState &S, CodePtr OpPC, bool Extern,
         // Diagnose as non-const read.
         diagnoseNonConstVariable(S, OpPC, VD);
       } else {
-        const SourceInfo &Loc = S.Current->getSource(OpPC);
         // Diagnose as "read of object outside its lifetime".
-        S.FFDiag(Loc, diag::note_constexpr_access_uninit)
+        S.FFDiag(S.Current->getSource(OpPC), diag::note_constexpr_access_uninit)
             << AK << /*IsIndeterminate=*/false;
-        S.Note(VD->getLocation(), diag::note_declared_at);
+        S.Note(VD->getFirstDecl()->getLocation(), diag::note_declared_at);
       }
       return false;
     }
diff --git a/clang/test/AST/ByteCode/cxx11.cpp b/clang/test/AST/ByteCode/cxx11.cpp
index 3553ab3ba68ad..1e3668f8f2e99 100644
--- a/clang/test/AST/ByteCode/cxx11.cpp
+++ b/clang/test/AST/ByteCode/cxx11.cpp
@@ -233,6 +233,13 @@ namespace ExternPointer {
   constexpr const int *pua = &pu.a; // Ok.
 }
 
+namespace ExternRedecl {
+  extern const int q; // both-note {{declared here}}
+  constexpr int g() { return q; } // both-note {{outside its lifetime}}
+  constexpr int q = g(); // both-error {{constant expression}} \
+                         // both-note {{in call}}
+}
+
 namespace PseudoDtor {
   typedef int I;
   constexpr int f(int a = 1) { // both-error {{never produces a constant expression}} \