[PATCH] D111883: [Parse] Improve diagnostic and recoveryy when there is an extra override in the outline method definition.

[Haojian Wu via Phabricator via cfe-commits]

hokein created this revision.
hokein added a reviewer: sammccall.
hokein requested review of this revision.
Herald added a project: clang.

The clang behavior was poor before this patch:

  void B::foo() override {}
  // Before: clang emited "expcted function body after function
  // declarator", and skiped all contents until it hits a ";", the
  // following function f() is discarded.
  
  // VS
  
  // Nnow "override is not allowed" with a remove fixit, and following f()
  // is retained.
  void f();


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D111883

Files:
  clang/include/clang/Basic/DiagnosticParseKinds.td
  clang/lib/Parse/ParseDecl.cpp
  clang/test/Parser/cxx-extra-virtual-specifiers.cpp


Index: clang/test/Parser/cxx-extra-virtual-specifiers.cpp
===================================================================
--- /dev/null
+++ clang/test/Parser/cxx-extra-virtual-specifiers.cpp
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -fdiagnostics-parseable-fixits %s
+
+class A {
+  virtual void foo();
+};
+class B : public A {
+  void foo() override;
+};
+
+void B::foo() override {} // expected-error {{'override' virt-specifier is not allowed outside a class definition}}
+                          // CHECK: fix-it:"{{.*}}":{[[@LINE-1]]:15-[[@LINE-1]]:24}:""
+
+void f1() override; // expected-error {{'override' virt-specifier is not allowed}}
+
+void f2() override {} // expected-error {{'override' virt-specifier is not allowed}}
+
+void test() {
+  void f() override; // expected-error {{'override' virt-specifier is not allowed}}
+}
Index: clang/lib/Parse/ParseDecl.cpp
===================================================================
--- clang/lib/Parse/ParseDecl.cpp
+++ clang/lib/Parse/ParseDecl.cpp
@@ -2021,6 +2021,18 @@
       Actions.CodeCompleteAfterFunctionEquals(D);
       return nullptr;
     }
+    // We're at the point where the parsing of function declarator is finished.
+    //
+    // A common error is that users accidently add a virtual specifier
+    // (e.g. override) in an out-line method definition.
+    // We attempt to recover by stripping all these specifiers coming after
+    // the declarator.
+    while (auto Specifier = isCXX11VirtSpecifier()) {
+      Diag(Tok, diag::err_virt_specifier_outside_class)
+          << VirtSpecifiers::getSpecifierName(Specifier)
+          << FixItHint::CreateRemoval(Tok.getLocation());
+      ConsumeToken();
+    }
     // Look at the next token to make sure that this isn't a function
     // declaration.  We have to check this because __attribute__ might be the
     // start of a function definition in GCC-extended K&R C.
Index: clang/include/clang/Basic/DiagnosticParseKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticParseKinds.td
+++ clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -944,6 +944,9 @@
 def err_duplicate_virt_specifier : Error<
   "class member already marked '%0'">;
 
+def err_virt_specifier_outside_class : Error<
+  "'%0' virt-specifier is not allowed outside a class definition">;
+
 def err_expected_parameter_pack : Error<
   "expected the name of a parameter pack">;
 def err_paren_sizeof_parameter_pack : Error<


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