llvmbot wrote:

<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: cor3ntin (cor3ntin)

<details>
<summary>Changes</summary>

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 https://github.com/llvm/llvm-project/issues/138657
Fixes https://github.com/llvm/llvm-project/issues/115725
Fixes https://github.com/llvm/llvm-project/issues/68852

---
Full diff: https://github.com/llvm/llvm-project/pull/139246.diff


3 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+1) 
- (modified) clang/lib/Sema/SemaExpr.cpp (+30) 
- (modified) clang/test/SemaTemplate/fun-template-def.cpp (+97-1) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 203958dab7430..bdd54f6a52b05 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -655,6 +655,7 @@ 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..abfc147045bbb 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -6541,6 +6541,28 @@ 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, const Expr* E) {
+    QualType T = E->getType();
+    if(T->isDependentType())
+        return true;
+
+    if( T == Context.BoundMemberTy || T == Context.UnknownAnyTy ||
+        T == Context.BuiltinFnTy || T == Context.OverloadTy ||
+        T->isFunctionType() || T->isFunctionReferenceType() ||
+        T->isMemberFunctionPointerType() || T->isFunctionPointerType() ||
+        T->isBlockPointerType() || T->isRecordType())
+        return true;
+
+    return isa<CallExpr,
+               DeclRefExpr,
+               MemberExpr,
+               CXXPseudoDestructorExpr,
+               OverloadExpr,
+               UnresolvedMemberExpr,
+               UnaryOperator>(E);
+}
+
 ExprResult Sema::BuildCallExpr(Scope *Scope, Expr *Fn, SourceLocation 
LParenLoc,
                                MultiExprArg ArgExprs, SourceLocation RParenLoc,
                                Expr *ExecConfig, bool IsExecConfig,
@@ -6594,6 +6616,14 @@ 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 (!MayBeFunctionType(Context, Fn))
+          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..e666326202521 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);
   u1(i1, t1);
 
   U u2 = (T)i1;
@@ -60,3 +61,98 @@ 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@-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@-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@-1 {{in instantiation of template}}
+auto k = c_<1>; // expected-note {{in instantiation of variable}}
+
+}
+
+namespace GH138731 {
+template <class...>
+using void_t = void;
+template <class...>
+using void_t = void;
+
+template <class T>
+T&& declval();
+
+struct S {
+  S();
+  static int f();
+  static int var;
+};
+
+namespace invoke_detail {
+
+template <typename F>
+struct traits {
+  template <typename... A>
+  using result = decltype(declval<F>()(declval<A>()...));
+};
+
+template <typename F, typename... A>
+using invoke_result_t = typename traits<F>::template result<A...>;
+
+template <typename Void, typename F, typename... A>
+inline constexpr bool is_invocable_v = false;
+
+template <typename F, typename... A>
+inline constexpr bool
+    is_invocable_v<void_t<invoke_result_t<F, A...>>, F, A...> = true;
+
+}
+
+template <typename F, typename... A>
+inline constexpr bool is_invocable_v =
+    invoke_detail::is_invocable_v<void, F, A...>;
+
+static_assert(!is_invocable_v<int>);
+static_assert(!is_invocable_v<int, int>);
+static_assert(!is_invocable_v<S>);
+static_assert(is_invocable_v<decltype(&S::f)>);
+static_assert(!is_invocable_v<decltype(&S::var)>);
+
+}
+
+#endif

``````````

</details>


https://github.com/llvm/llvm-project/pull/139246
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