[clang] 289baf1 - [clang][AST] Handle implicit first argument in CallExpr::getBeginLoc() (#135757)

[via cfe-commits]

Author: Nathan Ridge
Date: 2025-04-15T12:04:35-04:00
New Revision: 289baf1f42c8b5773271b611cd235d4ab94bb4e8

URL: https://github.com/llvm/llvm-project/commit/289baf1f42c8b5773271b611cd235d4ab94bb4e8
DIFF: https://github.com/llvm/llvm-project/commit/289baf1f42c8b5773271b611cd235d4ab94bb4e8.diff

LOG: [clang][AST] Handle implicit first argument in CallExpr::getBeginLoc() (#135757)

Fixes https://github.com/llvm/llvm-project/issues/135522

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/AST/Expr.cpp
    clang/test/SemaCXX/cxx2b-deducing-this.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 2d2606085998c..c106148855436 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -411,6 +411,8 @@ Bug Fixes in This Version
 - ``#embed`` directive now diagnoses use of a non-character file (device file)
   such as ``/dev/urandom`` as an error. This restriction may be relaxed in the
   future. See (#GH126629).
+- Fixed a clang 20 regression where diagnostics attached to some calls to member functions
+  using C++23 "deducing this" did not have a diagnostic location (#GH135522)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

diff  --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 5fab2c73f214b..59c0e47c7c195 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -1652,8 +1652,11 @@ SourceLocation CallExpr::getBeginLoc() const {
   if (!isTypeDependent()) {
     if (const auto *Method =
             dyn_cast_if_present<const CXXMethodDecl>(getCalleeDecl());
-        Method && Method->isExplicitObjectMemberFunction())
-      return getArg(0)->getBeginLoc();
+        Method && Method->isExplicitObjectMemberFunction()) {
+      if (auto FirstArgLoc = getArg(0)->getBeginLoc(); FirstArgLoc.isValid()) {
+        return FirstArgLoc;
+      }
+    }
   }
 
   SourceLocation begin = getCallee()->getBeginLoc();

diff  --git a/clang/test/SemaCXX/cxx2b-deducing-this.cpp b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
index 6f17ce7275456..7e392213710a4 100644
--- a/clang/test/SemaCXX/cxx2b-deducing-this.cpp
+++ b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
@@ -1134,3 +1134,10 @@ struct S {
 static_assert((S{} << 11) == a);
 // expected-error at -1 {{use of undeclared identifier 'a'}}
 }
+
+namespace GH135522 {
+struct S {
+  auto f(this auto) -> S;
+  bool g() { return f(); } // expected-error {{no viable conversion from returned value of type 'S' to function return type 'bool'}}
+};
+}