Diagnose function template definitions inside functions

The parser can only be tricked into parsing a function template
definition by inserting a typename keyword before the function template
declaration. This used to make us crash, and now it's fixed.

While here, remove an unneeded boolean parameter from ParseDeclGroup.
This boolean always corresponded to non-typedef declarators at file
scope. ParseDeclGroup already has precise diagnostics for the function
definition typedef case, so we can let that through.

Fixes PR21839.

llvm-svn: 224287

clang/include/clang/Parse/Parser.h

@@ -1728,7 +1728,6 @@ private:
                                         ForRangeInit *FRI = nullptr);
   bool MightBeDeclarator(unsigned Context);
   DeclGroupPtrTy ParseDeclGroup(ParsingDeclSpec &DS, unsigned Context,
-                                bool AllowFunctionDefinitions,
                                 SourceLocation *DeclEnd = nullptr,
                                 ForRangeInit *FRI = nullptr);
   Decl *ParseDeclarationAfterDeclarator(Declarator &D,

clang/lib/Parse/ParseDecl.cpp

@@ -1466,7 +1466,7 @@ Parser::ParseSimpleDeclaration(unsigned Context,
   }
 
   DS.takeAttributesFrom(Attrs);
-  return ParseDeclGroup(DS, Context, /*FunctionDefs=*/ false, &DeclEnd, FRI);
+  return ParseDeclGroup(DS, Context, &DeclEnd, FRI);
 }
 
 /// Returns true if this might be the start of a declarator, or a common typo
@@ -1621,7 +1621,6 @@ void Parser::SkipMalformedDecl() {
 /// result.
 Parser::DeclGroupPtrTy Parser::ParseDeclGroup(ParsingDeclSpec &DS,
                                               unsigned Context,
-                                              bool AllowFunctionDefinitions,
                                               SourceLocation *DeclEnd,
                                               ForRangeInit *FRI) {
   // Parse the first declarator.
@@ -1669,7 +1668,10 @@ Parser::DeclGroupPtrTy Parser::ParseDeclGroup(ParsingDeclSpec &DS,
       // start of a function definition in GCC-extended K&R C.
       !isDeclarationAfterDeclarator()) {
 
-    if (AllowFunctionDefinitions) {
+    // Function definitions are only allowed at file scope and in C++ classes.
+    // The C++ inline method definition case is handled elsewhere, so we only
+    // need to handle the file scope definition case.
+    if (Context == Declarator::FileContext) {
       if (isStartOfFunctionDefinition(D)) {
         if (DS.getStorageClassSpec() == DeclSpec::SCS_typedef) {
           Diag(Tok, diag::err_function_declared_typedef);

clang/lib/Parse/ParseTemplate.cpp

@@ -231,6 +231,16 @@ Parser::ParseSingleDeclarationAfterTemplate(
 
   if (DeclaratorInfo.isFunctionDeclarator() &&
       isStartOfFunctionDefinition(DeclaratorInfo)) {
+
+    // Function definitions are only allowed at file scope and in C++ classes.
+    // The C++ inline method definition case is handled elsewhere, so we only
+    // need to handle the file scope definition case.
+    if (Context != Declarator::FileContext) {
+      Diag(Tok, diag::err_function_definition_not_allowed);
+      SkipMalformedDecl();
+      return nullptr;
+    }
+
     if (DS.getStorageClassSpec() == DeclSpec::SCS_typedef) {
       // Recover by ignoring the 'typedef'. This was probably supposed to be
       // the 'typename' keyword, which we should have already suggested adding

clang/lib/Parse/Parser.cpp

@@ -890,7 +890,7 @@ Parser::ParseDeclOrFunctionDefInternal(ParsedAttributesWithRange &attrs,
     return Actions.ConvertDeclToDeclGroup(TheDecl);
   }
 
-  return ParseDeclGroup(DS, Declarator::FileContext, true);
+  return ParseDeclGroup(DS, Declarator::FileContext);
 }
 
 Parser::DeclGroupPtrTy

clang/test/CXX/drs/dr5xx.cpp

@@ -798,7 +798,7 @@ namespace dr575 { // dr575: yes
 }
 
 namespace dr576 { // dr576: yes
-  typedef void f() {} // expected-error {{function definition is not allowed}}
+  typedef void f() {} // expected-error {{function definition declared 'typedef'}}
   void f(typedef int n); // expected-error {{invalid storage class}}
   void f(char c) { typedef int n; }
 }

clang/test/Parser/cxx-template-decl.cpp

@@ -211,6 +211,19 @@ void Instantiate() {
 
 }
 
+namespace func_tmpl_spec_def_in_func {
+// We failed to diagnose function template specialization definitions inside
+// functions during recovery previously.
+template <class> void FuncTemplate() {}
+void TopLevelFunc() {
+  // expected-error@+2 {{expected a qualified name after 'typename'}}
+  // expected-error@+1 {{function definition is not allowed here}}
+  typename template <> void FuncTemplate<void>() { }
+  // expected-error@+1 {{function definition is not allowed here}}
+  void NonTemplateInner() { }
+}
+}
+
 namespace broken_baseclause {
 template<typename T>
 struct base { };