[PATCH] D113838: Sema: Don't erroneously reject `void{}`

[Aaron Puchert via Phabricator via cfe-commits]

aaronpuchert created this revision.
aaronpuchert added a reviewer: rsmith.
aaronpuchert requested review of this revision.
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This is explicitly allowed via [expr.type.conv], if the initialization
list is empty.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113838

Files:
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaInit.cpp
  clang/test/CXX/expr/expr.post/expr.type.conv/p2.cpp
  clang/test/SemaCXX/attr-annotate.cpp
  clang/test/SemaCXX/cxx2a-explicit-bool.cpp


Index: clang/test/SemaCXX/cxx2a-explicit-bool.cpp
===================================================================
--- clang/test/SemaCXX/cxx2a-explicit-bool.cpp
+++ clang/test/SemaCXX/cxx2a-explicit-bool.cpp
@@ -73,8 +73,8 @@
 
 template <typename T> struct E {
   // expected-note at -1+ {{candidate constructor}}
-  explicit((T{}, false))
-  // expected-error at -1 {{illegal initializer type 'void'}}
+  explicit(((T&&)T{}, false))
+  // expected-error at -1 {{cannot form a reference to 'void'}}
   E(int);
 };
 
Index: clang/test/SemaCXX/attr-annotate.cpp
===================================================================
--- clang/test/SemaCXX/attr-annotate.cpp
+++ clang/test/SemaCXX/attr-annotate.cpp
@@ -42,8 +42,8 @@
 
   template<typename T>
   struct B {
-    [[clang::annotate("test", ((void)T{}, 9))]] void t() {}
-    // expected-error at -1 {{illegal initializer type 'void'}}
+    [[clang::annotate("test", ((void)T{1}, 9))]] void t() {}
+    // expected-error at -1 {{initializer list for 'void' must be empty}}
   };
   B<int> b;
   B<void> b1;
Index: clang/test/CXX/expr/expr.post/expr.type.conv/p2.cpp
===================================================================
--- /dev/null
+++ clang/test/CXX/expr/expr.post/expr.type.conv/p2.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -std=c++11 -verify %s
+
+void paren_list() {
+  return void();
+}
+
+void brace_list() {
+  return void{};
+}
+
+void brace_list_nonempty() {
+  return void{1}; // expected-error {{initializer list for 'void' must be empty}}
+}
+
+void brace_list_nested_nonempty() {
+  return void{{}}; // expected-error {{initializer list for 'void' must be empty}}
+}
Index: clang/lib/Sema/SemaInit.cpp
===================================================================
--- clang/lib/Sema/SemaInit.cpp
+++ clang/lib/Sema/SemaInit.cpp
@@ -1308,7 +1308,16 @@
     CheckArrayType(Entity, IList, DeclType, Zero,
                    SubobjectIsDesignatorContext, Index,
                    StructuredList, StructuredIndex);
-  } else if (DeclType->isVoidType() || DeclType->isFunctionType()) {
+  } else if (DeclType->isVoidType()) {
+    // [expr.type.conv]p2: Otherwise, if the type is cv void and the
+    // initializer is () or {} (after pack expansion, if any), the expression
+    // is a prvalue of type void that performs no initialization.
+    if (IList->getNumInits() > 0) {
+      if (!VerifyOnly)
+        SemaRef.Diag(IList->getBeginLoc(), diag::err_init_list_void_nonempty);
+      hadError = true;
+    }
+  } else if (DeclType->isFunctionType()) {
     // This type is invalid, issue a diagnostic.
     ++Index;
     if (!VerifyOnly)
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5845,6 +5845,8 @@
 def err_illegal_initializer : Error<
   "illegal initializer (only variables can be initialized)">;
 def err_illegal_initializer_type : Error<"illegal initializer type %0">;
+def err_init_list_void_nonempty : Error<
+  "initializer list for 'void' must be empty">;
 def ext_init_list_type_narrowing : ExtWarn<
   "type %0 cannot be narrowed to %1 in initializer list">,
   InGroup<CXX11Narrowing>, DefaultError, SFINAEFailure;


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