[clang] [Clang] correct error message when assigning to const reference captured in lambda (PR #105647)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (nfrmtk)

<details>
<summary>Changes</summary>

Fixes:#<!-- -->98772

---
Full diff: https://github.com/llvm/llvm-project/pull/105647.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaExpr.cpp (+2) 
- (modified) clang/test/SemaCXX/lambda-expressions.cpp (+5) 


``````````diff
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index c67183df335dd5..9c256fd1ed1a41 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -13140,6 +13140,8 @@ static NonConstCaptureKind isReferenceToNonConstCapture(Sema &S, Expr *E) {
   VarDecl *var = dyn_cast<VarDecl>(DRE->getDecl());
   if (!var) return NCCK_None;
   if (var->getType().isConstQualified()) return NCCK_None;
+  if (var->getType()->isReferenceType())
+    return NCCK_None;
   assert(var->hasLocalStorage() && "capture added 'const' to non-local?");
 
   // Decide whether the first capture was for a block or a lambda.
diff --git a/clang/test/SemaCXX/lambda-expressions.cpp b/clang/test/SemaCXX/lambda-expressions.cpp
index acf8d014a9896b..612c6db950f273 100644
--- a/clang/test/SemaCXX/lambda-expressions.cpp
+++ b/clang/test/SemaCXX/lambda-expressions.cpp
@@ -189,6 +189,11 @@ namespace ModifyingCapture {
     [=] {
       n = 1; // expected-error {{cannot assign to a variable captured by copy in a non-mutable lambda}}
     };
+    const int cn = 0;
+    // cxx03-cxx11-warning at +1 {{initialized lambda captures are a C++14 extension}}
+    [&cnr = cn]{ // expected-note {{variable 'cnr' declared const here}}
+      cnr = 1; // expected-error {{cannot assign to variable 'cnr' with const-qualified type 'const int &'}}
+    };
   }
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/105647