From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Sun, 6 Oct 2019 18:40:59 +0000 (+0000)
Subject: [Sema] Avoids an assertion failure when an invalid conversion declaration is used
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c059e0ac05e9795b065bbbe18159f52fdf1f7086;p=clang

[Sema] Avoids an assertion failure when an invalid conversion declaration is used

Summary:
When using a user-defined conversion function template with a deduced return type the compiler gives a set of warnings:
```
bug.cc:252:44: error: cannot specify any part of a return type in the declaration of a conversion function; use an alias template to declare a conversion to 'auto (Ts &&...) const'
  template <typename... Ts> operator auto()(Ts &&... xs) const;
                                           ^~~~~~~~~~~~~~~~~~~
bug.cc:252:29: error: conversion function cannot convert to a function type
  template <typename... Ts> operator auto()(Ts &&... xs) const;
                            ^
error: pointer to function type cannot have 'const' qualifier
```
after which it triggers an assertion failure. It seems the last error is incorrect and doesn't have any location information. This patch stops the compilation after the second warning.

Fixes bug 31422.

Patch by Mark de Wever!

Reviewers: rsmith

Reviewed By: rsmith

Subscribers: bbannier, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64820

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@373862 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 7a169ba51a..6114eb8e8d 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -8206,6 +8206,9 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     }
 
     SemaRef.CheckConversionDeclarator(D, R, SC);
+    if (D.isInvalidType())
+      return nullptr;
+
     IsVirtualOkay = true;
     return CXXConversionDecl::Create(
         SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
diff --git a/test/SemaCXX/PR31422.cpp b/test/SemaCXX/PR31422.cpp
new file mode 100644
index 0000000000..0ac321d7af
--- /dev/null
+++ b/test/SemaCXX/PR31422.cpp
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify %s
+
+// expected-error@+3 {{cannot specify any part of a return type in the declaration of a conversion function; use an alias template to declare a conversion to 'auto (Ts &&...) const'}}
+// expected-error@+2 {{conversion function cannot convert to a function type}}
+struct S {
+  template <typename... Ts> operator auto()(Ts &&... xs) const;
+};