[C++17] Fix class template argument deduction for default constructors without an initializer

Summary:
As the title says, this makes following code compile:

```
template<typename> struct Foo {};
Foo() -> Foo<void>;

Foo f; // ok
```

Thanks Nicolas Lesser for coining the fix.

Reviewers: rsmith, lichray

Reviewed By: rsmith, lichray

Subscribers: lichray, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D38216

llvm-svn: 328409

1 files changed, 1 insertions, 2 deletions

diff --git a/clang/test/Parser/cxx1z-class-template-argument-deduction.cpp b/clang/test/Parser/cxx1z-class-template-argument-deduction.cpp
index bf1d004c8d2..532c893f213 100644
--- a/clang/test/Parser/cxx1z-class-template-argument-deduction.cpp
+++ b/clang/test/Parser/cxx1z-class-template-argument-deduction.cpp
@@ -137,7 +137,6 @@ namespace expr {
     (void)A{n};
     (void)new A(n);
     (void)new A{n};
-    // FIXME: We should diagnose the lack of an initializer here.
     (void)new A;
   }
 }
@@ -150,7 +149,7 @@ namespace decl {
 
   auto k() -> A; // expected-error{{requires template arguments}}
 
-  A a; // expected-error {{declaration of variable 'a' with deduced type 'A' requires an initializer}}
+  A a;
   A b = 0;
   const A c = 0;
   A (parens) = 0; // expected-error {{cannot use parentheses when declaring variable with deduced class template specialization type}}