[Clang] Workaround dependent source location issues (#106925)

clang/docs/ReleaseNotes.rst

@@ -1121,6 +1121,8 @@ Bug Fixes to C++ Support
   Fixes (#GH85992).
 - Fixed a crash-on-invalid bug involving extraneous template parameter with concept substitution. (#GH73885)
 - Fixed assertion failure by skipping the analysis of an invalid field declaration. (#GH99868)
+- Fix an issue with dependent source location expressions (#GH106428), (#GH81155), (#GH80210), (#GH85373)
+
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Sema/SemaExpr.cpp

@@ -5430,11 +5430,24 @@ struct EnsureImmediateInvocationInDefaultArgs
 
   // Rewrite to source location to refer to the context in which they are used.
   ExprResult TransformSourceLocExpr(SourceLocExpr *E) {
-    if (E->getParentContext() == SemaRef.CurContext)
+    DeclContext *DC = E->getParentContext();
+    if (DC == SemaRef.CurContext)
       return E;
-    return getDerived().RebuildSourceLocExpr(E->getIdentKind(), E->getType(),
-                                             E->getBeginLoc(), E->getEndLoc(),
-                                             SemaRef.CurContext);
+
+    // FIXME: During instantiation, because the rebuild of defaults arguments
+    // is not always done in the context of the template instantiator,
+    // we run the risk of producing a dependent source location
+    // that would never be rebuilt.
+    // This usually happens during overload resolution, or in contexts
+    // where the value of the source location does not matter.
+    // However, we should find a better way to deal with source location
+    // of function templates.
+    if (!SemaRef.CurrentInstantiationScope ||
+        !SemaRef.CurContext->isDependentContext() || DC->isDependentContext())
+      DC = SemaRef.CurContext;
+
+    return getDerived().RebuildSourceLocExpr(
+        E->getIdentKind(), E->getType(), E->getBeginLoc(), E->getEndLoc(), DC);
   }
 };
 

clang/test/SemaCXX/source_location.cpp

@@ -929,3 +929,63 @@ void test() {
 }
 
 }
+
+namespace GH106428 {
+
+struct add_fn {
+    template <typename T>
+    constexpr auto operator()(T lhs, T rhs,
+                              const std::source_location loc = std::source_location::current())
+        const -> T
+    {
+        return lhs + rhs;
+    }
+};
+
+
+template <class _Fp, class... _Args>
+decltype(_Fp{}(0, 0))
+__invoke(_Fp&& __f);
+
+template<typename T>
+struct type_identity { using type = T; };
+
+template<class Fn>
+struct invoke_result : type_identity<decltype(__invoke(Fn{}))> {};
+
+using i = invoke_result<add_fn>::type;
+static_assert(__is_same(i, int));
+
+}
+
+#if __cplusplus >= 202002L
+
+namespace GH81155 {
+struct buff {
+  buff(buff &, const char * = __builtin_FUNCTION());
+};
+
+template <class Ty>
+Ty declval();
+
+template <class Fx>
+auto Call(buff arg) -> decltype(Fx{}(arg));
+
+template <typename>
+struct F {};
+
+template <class Fx>
+struct InvocableR : F<decltype(Call<Fx>(declval<buff>()))> {
+  static constexpr bool value = false;
+};
+
+template <class Fx, bool = InvocableR<Fx>::value>
+void Help(Fx) {}
+
+void Test() {
+  Help([](buff) {});
+}
+
+}
+
+#endif