[clang] Fix a crash when CTAD fails

Differential Revision: https://reviews.llvm.org/D99145

Author: kadircet

clang/lib/Sema/SemaChecking.cpp

@@ -4492,7 +4492,8 @@ void Sema::CheckArgAlignment(SourceLocation Loc, NamedDecl *FDecl,
 
   // Find expected alignment, and the actual alignment of the passed object.
   // getTypeAlignInChars requires complete types
-  if (ParamTy->isIncompleteType() || ArgTy->isIncompleteType())
+  if (ParamTy->isIncompleteType() || ArgTy->isIncompleteType() ||
+      ParamTy->isUndeducedType() || ArgTy->isUndeducedType())
     return;
 
   CharUnits ParamAlign = Context.getTypeAlignInChars(ParamTy);

clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp

@@ -543,6 +543,18 @@ namespace PR47175 {
   int m = n<int>;
 }
 
+// Ensure we don't crash when CTAD fails.
+template <typename T1, typename T2>
+struct Foo {   // expected-note{{candidate function template not viable}}
+  Foo(T1, T2); // expected-note{{candidate function template not viable}}
+};
+
+template <typename... Args>
+void insert(Args &&...args);
+
+void foo() {
+  insert(Foo(2, 2, 2)); // expected-error{{no viable constructor or deduction guide}}
+}
 #else
 
 // expected-no-diagnostics