[Sema] Fix a structured binding typo correction bug

BindingDecls have null type until their initializer is processed, so we can't
assume that a correction candidate has non-null type.

rdar://41559582

llvm-svn: 336634

clang/lib/Sema/SemaLookup.cpp

@@ -4990,6 +4990,8 @@ bool FunctionCallFilterCCC::ValidateCandidate(const TypoCorrection &candidate) {
         // determine if it is a pointer or reference to a function. If so,
         // check against the number of arguments expected for the pointee.
         QualType ValType = cast<ValueDecl>(ND)->getType();
+        if (ValType.isNull())
+          continue;
         if (ValType->isAnyPointerType() || ValType->isReferenceType())
           ValType = ValType->getPointeeType();
         if (const FunctionProtoType *FPT = ValType->getAs<FunctionProtoType>())

clang/test/SemaCXX/typo-correction-cxx17.cpp

@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -std=c++1z -fsyntax-only -verify %s
+
+namespace decomp_decl {
+void f() {
+	auto [this_is_a_typo] = this_is_a_typp(); // expected-error{{use of undeclared identifier 'this_is_a_typp'}}
+}
+}