[clang] cf9b4d1 - [Clang] Diagnose invalid function types in dependent contexts (#138731)

[via cfe-commits]

Author: cor3ntin
Date: 2025-05-06T22:51:04+02:00
New Revision: cf9b4d1e7961214deabd99a9fc3b1d4c9e78a71f

URL: https://github.com/llvm/llvm-project/commit/cf9b4d1e7961214deabd99a9fc3b1d4c9e78a71f
DIFF: https://github.com/llvm/llvm-project/commit/cf9b4d1e7961214deabd99a9fc3b1d4c9e78a71f.diff

LOG: [Clang] Diagnose invalid function types in dependent contexts (#138731)

When forming an invalid function type, we were not diagnosing it if the
call was dependent.

However, we later rely on the function type to be sensible during
argument deduction.

We now diagnose anything that is not a potential function type, to avoid
constructing bogus call expressions.

Fixes #138657
Fixes #115725
Fixes #68852

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/Sema/SemaExpr.cpp
    clang/test/SemaTemplate/fun-template-def.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a4107bfaf913d..f40ebe9764892 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -657,6 +657,7 @@ Bug Fixes to C++ Support
 - Fixed an assertion when trying to constant-fold various builtins when the argument
   referred to a reference to an incomplete type. (#GH129397)
 - Fixed a crash when a cast involved a parenthesized aggregate initialization in dependent context. (#GH72880)
+- Fixed a crash when forming an invalid function type in a dependent context. (#GH138657) (#GH115725) (#GH68852)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

diff  --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index be3f145f3c5f1..6e8aa1a362c50 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -6541,6 +6541,15 @@ ExprResult Sema::ActOnCallExpr(Scope *Scope, Expr *Fn, SourceLocation LParenLoc,
   return Call;
 }
 
+// Any type that could be used to form a callable expression
+static bool MayBeFunctionType(const ASTContext &Context, QualType T) {
+  return T == Context.BoundMemberTy || T == Context.UnknownAnyTy ||
+         T == Context.BuiltinFnTy || T == Context.OverloadTy ||
+         T->isFunctionType() || T->isFunctionReferenceType() ||
+         T->isMemberFunctionPointerType() || T->isFunctionPointerType() ||
+         T->isBlockPointerType() || T->isRecordType();
+}
+
 ExprResult Sema::BuildCallExpr(Scope *Scope, Expr *Fn, SourceLocation LParenLoc,
                                MultiExprArg ArgExprs, SourceLocation RParenLoc,
                                Expr *ExecConfig, bool IsExecConfig,
@@ -6594,6 +6603,15 @@ ExprResult Sema::BuildCallExpr(Scope *Scope, Expr *Fn, SourceLocation LParenLoc,
             *this, dyn_cast<UnresolvedMemberExpr>(Fn->IgnoreParens()),
             Fn->getBeginLoc());
 
+        // If the type of the function itself is not dependent
+        // check that it is a reasonable as a function, as type deduction
+        // later assume the CallExpr has a sensible TYPE.
+        if (!Fn->getType()->isDependentType() &&
+            !MayBeFunctionType(Context, Fn->getType()))
+          return ExprError(
+              Diag(LParenLoc, diag::err_typecheck_call_not_function)
+              << Fn->getType() << Fn->getSourceRange());
+
         return CallExpr::Create(Context, Fn, ArgExprs, Context.DependentTy,
                                 VK_PRValue, RParenLoc, CurFPFeatureOverrides());
       }

diff  --git a/clang/test/SemaTemplate/fun-template-def.cpp b/clang/test/SemaTemplate/fun-template-def.cpp
index de77901b5b601..716296e72bc44 100644
--- a/clang/test/SemaTemplate/fun-template-def.cpp
+++ b/clang/test/SemaTemplate/fun-template-def.cpp
@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++98 %s
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
 
 // Tests that dependent expressions are always allowed, whereas non-dependent
 // are checked as usual.
@@ -32,7 +33,7 @@ T f1(T t1, U u1, int i1, T** tpp)
   i1 = t1[u1];
   i1 *= t1;
 
-  i1(u1, t1); // error
+  i1(u1, t1); // expected-error {{called object type 'int' is not a function or function pointer}}
   u1(i1, t1);
 
   U u2 = (T)i1;
@@ -60,3 +61,51 @@ void f3() {
   f2<int*>(0);
   f2<int>(0); // expected-error {{no matching function for call to 'f2'}}
 }
+
+#if __cplusplus >= 202002L
+namespace GH138657 {
+template <auto V> // #gh138657-template-head
+class meta {};
+template<int N>
+class meta<N()> {}; // expected-error {{called object type 'int' is not a function or function point}}
+
+template<int N[1]>
+class meta<N()> {}; // expected-error {{called object type 'int *' is not a function or function point}}
+
+template<char* N>
+class meta<N()> {}; // expected-error {{called object type 'char *' is not a function or function point}}
+
+struct S {};
+template<S>
+class meta<S()> {}; // expected-error {{template argument for non-type template parameter is treated as function type 'S ()'}}
+                    // expected-note@#gh138657-template-head {{template parameter is declared here}}
+
+}
+
+namespace GH115725 {
+template<auto ...> struct X {};
+template<typename T, typename ...Ts> struct A {
+  template<Ts ...Ns, T *...Ps>
+  A(X<0(Ps)...>, Ts (*...qs)[Ns]);
+  // expected-error at -1{{called object type 'int' is not a function or function pointer}}
+
+};
+}
+
+namespace GH68852 {
+template <auto v>
+struct constexpr_value {
+  template <class... Ts>
+  constexpr constexpr_value<v(Ts::value...)> call(Ts...) {
+    //expected-error at -1 {{called object type 'int' is not a function or function pointer}}
+    return {};
+  }
+};
+
+template <auto v> constexpr static inline auto c_ = constexpr_value<v>{};
+// expected-note at -1 {{in instantiation of template}}
+auto k = c_<1>; // expected-note {{in instantiation of variable}}
+
+}
+
+#endif