Improve diagnostics when the parser encounters a declarator with an

unknown type name, e.g.,

  foo::bar x;

when "bar" does not refer to a type in "foo". 

With this change, the parser now calls into the action to perform
diagnostics and can try to recover by substituting in an appropriate
type. For example, this allows us to easily diagnose some missing
"typename" specifiers, which we now do:

  test/SemaCXX/unknown-type-name.cpp:29:1: error: missing 'typename'
        prior to dependent type name 'A<T>::type'
  A<T>::type A<T>::f() { return type(); }
  ^~~~~~~~~~
  typename 

Fixes PR3990.

llvm-svn: 84053

12 files changed, 141 insertions, 20 deletions

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 0aeefb3ee90..9e50ca65fbe 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -104,7 +104,7 @@ def err_using_requires_qualname : Error<
 def err_using_typename_non_type : Error<
   "'typename' keyword used on a non-type">;
 def err_using_decl_nested_name_specifier_is_not_a_base_class : Error<
-  "using declaration refers into %0, which is not a base class of %1">;
+  "using declaration refers into '%0', which is not a base class of %1">;
 def err_using_decl_can_not_refer_to_class_member : Error<
   "using declaration can not refer to class member">;
  def err_using_decl_can_not_refer_to_namespace : Error<
@@ -990,7 +990,7 @@ def err_template_spec_extra_headers : Error<
   "extraneous template parameter list in template specialization or "
   "out-of-line template definition">;
 def err_template_qualified_declarator_no_match : Error<
-  "nested name specifier %0 for declaration does not refer into a class, "
+  "nested name specifier '%0' for declaration does not refer into a class, "
   "class template or class template partial specialization">;
 
 // C++ Class Template Partial Specialization
@@ -1111,6 +1111,8 @@ def err_typename_nested_not_type : Error<
     "typename specifier refers to non-type member %0 in %1">;
 def note_typename_refers_here : Note<
     "referenced member %0 is declared here">;
+def err_typename_missing : Error<
+  "missing 'typename' prior to dependent type name '%0%1'">;
 
 def err_template_kw_refers_to_non_template : Error<
     "%0 following the 'template' keyword does not refer to a template">;
diff --git a/clang/include/clang/Parse/Action.h b/clang/include/clang/Parse/Action.h
index 5e0a360df19..1ee14701fa2 100644
--- a/clang/include/clang/Parse/Action.h
+++ b/clang/include/clang/Parse/Action.h
@@ -201,6 +201,36 @@ public:
     return DeclSpec::TST_unspecified;
   }
 
+  /// \brief Action called as part of error recovery when the parser has 
+  /// determined that the given name must refer to a type, but 
+  /// \c getTypeName() did not return a result.
+  ///
+  /// This callback permits the action to give a detailed diagnostic when an
+  /// unknown type name is encountered and, potentially, to try to recover
+  /// by producing a new type in \p SuggestedType.
+  ///
+  /// \param II the name that should be a type.
+  ///
+  /// \param IILoc the location of the name in the source.
+  ///
+  /// \param S the scope in which name lookup was performed.
+  ///
+  /// \param SS if non-NULL, the C++ scope specifier that preceded the name.
+  ///
+  /// \param SuggestedType if the action sets this type to a non-NULL type,
+  /// the parser will recovery by consuming the type name token and then 
+  /// pretending that the given type was the type it parsed.
+  ///
+  /// \returns true if a diagnostic was emitted, false otherwise. When false,
+  /// the parser itself will emit a generic "unknown type name" diagnostic.
+  virtual bool DiagnoseUnknownTypeName(const IdentifierInfo &II, 
+                                       SourceLocation IILoc,
+                                       Scope *S,
+                                       const CXXScopeSpec *SS,
+                                       TypeTy *&SuggestedType) {
+    return false;
+  }
+                                       
   /// isCurrentClassName - Return true if the specified name is the
   /// name of the innermost C++ class type currently being defined.
   virtual bool isCurrentClassName(const IdentifierInfo &II, Scope *S,
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index e15a4cd6880..b56c33170cb 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -688,13 +688,36 @@ bool Parser::ParseImplicitInt(DeclSpec &DS, CXXScopeSpec *SS,
     }
   }
 
-  // Since this is almost certainly an invalid type name, emit a
-  // diagnostic that says it, eat the token, and mark the declspec as
-  // invalid.
-  SourceRange R;
-  if (SS) R = SS->getRange();
+  // This is almost certainly an invalid type name. Let the action emit a 
+  // diagnostic and attempt to recover.
+  Action::TypeTy *T = 0;
+  if (Actions.DiagnoseUnknownTypeName(*Tok.getIdentifierInfo(), Loc,
+                                      CurScope, SS, T)) {
+    // The action emitted a diagnostic, so we don't have to.
+    if (T) {
+      // The action has suggested that the type T could be used. Set that as
+      // the type in the declaration specifiers, consume the would-be type
+      // name token, and we're done.
+      const char *PrevSpec;
+      unsigned DiagID;
+      DS.SetTypeSpecType(DeclSpec::TST_typename, Loc, PrevSpec, DiagID, T, 
+                         false);
+      DS.SetRangeEnd(Tok.getLocation());
+      ConsumeToken();
+      
+      // There may be other declaration specifiers after this.
+      return true;
+    }
+    
+    // Fall through; the action had no suggestion for us.
+  } else {
+    // The action did not emit a diagnostic, so emit one now.
+    SourceRange R;
+    if (SS) R = SS->getRange();
+    Diag(Loc, diag::err_unknown_typename) << Tok.getIdentifierInfo() << R;
+  }
 
-  Diag(Loc, diag::err_unknown_typename) << Tok.getIdentifierInfo() << R;
+  // Mark this as an error.
   const char *PrevSpec;
   unsigned DiagID;
   DS.SetTypeSpecType(DeclSpec::TST_error, Loc, PrevSpec, DiagID);
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index c289abfea86..ba05a07f265 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -117,6 +117,7 @@ static void ConvertArgToStringFn(Diagnostic::ArgumentKind Kind, intptr_t Val,
     llvm::raw_string_ostream OS(S);
     reinterpret_cast<NestedNameSpecifier*> (Val)->print(OS,
                                                         Context.PrintingPolicy);
+    NeedQuotes = false;
   } else {
     assert(Kind == Diagnostic::ak_declcontext);
     DeclContext *DC = reinterpret_cast<DeclContext *> (Val);
diff --git a/clang/lib/Sema/Sema.h b/clang/lib/Sema/Sema.h
index 465eca70ed3..04addfd3a98 100644
--- a/clang/lib/Sema/Sema.h
+++ b/clang/lib/Sema/Sema.h
@@ -523,7 +523,12 @@ public:
                               Scope *S, const CXXScopeSpec *SS,
                               bool isClassName = false);
   virtual DeclSpec::TST isTagName(IdentifierInfo &II, Scope *S);
-
+  virtual bool DiagnoseUnknownTypeName(const IdentifierInfo &II, 
+                                       SourceLocation IILoc,
+                                       Scope *S,
+                                       const CXXScopeSpec *SS,
+                                       TypeTy *&SuggestedType);
+  
   virtual DeclPtrTy ActOnDeclarator(Scope *S, Declarator &D) {
     return HandleDeclarator(S, D, MultiTemplateParamsArg(*this), false);
   }
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 9f03cb284ca..606b33f5f74 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -23,6 +23,7 @@
 #include "clang/AST/StmtCXX.h"
 #include "clang/AST/StmtObjC.h"
 #include "clang/Parse/DeclSpec.h"
+#include "clang/Parse/ParseDiagnostic.h"
 #include "clang/Basic/PartialDiagnostic.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
@@ -199,6 +200,36 @@ DeclSpec::TST Sema::isTagName(IdentifierInfo &II, Scope *S) {
   return DeclSpec::TST_unspecified;
 }
 
+bool Sema::DiagnoseUnknownTypeName(const IdentifierInfo &II, 
+                                   SourceLocation IILoc,
+                                   Scope *S,
+                                   const CXXScopeSpec *SS,
+                                   TypeTy *&SuggestedType) {
+  // We don't have anything to suggest (yet).
+  SuggestedType = 0;
+  
+  // FIXME: Should we move the logic that tries to recover from a missing tag
+  // (struct, union, enum) from Parser::ParseImplicitInt here, instead?
+  
+  if (!SS)
+    Diag(IILoc, diag::err_unknown_typename) << &II;
+  else if (DeclContext *DC = computeDeclContext(*SS, false))
+    Diag(IILoc, diag::err_typename_nested_not_found) 
+      << &II << DC << SS->getRange();
+  else if (isDependentScopeSpecifier(*SS)) {
+    Diag(SS->getRange().getBegin(), diag::err_typename_missing)
+      << (NestedNameSpecifier *)SS->getScopeRep() << II.getName() 
+      << SourceRange(SS->getRange().getBegin(), IILoc)
+      << CodeModificationHint::CreateInsertion(SS->getRange().getBegin(),
+                                               "typename ");
+    SuggestedType = ActOnTypenameType(SourceLocation(), *SS, II, IILoc).get();
+  } else {
+    assert(SS && SS->isInvalid() && 
+           "Invalid scope specifier has already been diagnosed");
+  }
+  
+  return true;
+}
 
 // Determines the context to return to after temporarily entering a
 // context.  This depends in an unnecessarily complicated way on the
diff --git a/clang/test/CXX/class/class.friend/p1.cpp b/clang/test/CXX/class/class.friend/p1.cpp
index 3f8778885ce..7065a7e917f 100644
--- a/clang/test/CXX/class/class.friend/p1.cpp
+++ b/clang/test/CXX/class/class.friend/p1.cpp
@@ -67,7 +67,7 @@ class A {
   class facet {};
 };
 
-A::UndeclaredSoFar y; // expected-error {{ unknown type name 'UndeclaredSoFar' }}
+A::UndeclaredSoFar y; // expected-error {{no type named 'UndeclaredSoFar' in 'class A'}}
 
 class PreDeclared;
 
diff --git a/clang/test/SemaCXX/namespace.cpp b/clang/test/SemaCXX/namespace.cpp
index ae8dfc58136..5ed6ba50ce1 100644
--- a/clang/test/SemaCXX/namespace.cpp
+++ b/clang/test/SemaCXX/namespace.cpp
@@ -67,4 +67,4 @@ namespace foo {
 
 static foo::x  test1;  // ok
 
-static foo::X  test2;  // typo: expected-error {{unknown type name 'X'}}
+static foo::X  test2;  // typo: expected-error {{no type named 'X' in}}
diff --git a/clang/test/SemaCXX/nested-name-spec.cpp b/clang/test/SemaCXX/nested-name-spec.cpp
index 4ddf3bbce4e..5178557030b 100644
--- a/clang/test/SemaCXX/nested-name-spec.cpp
+++ b/clang/test/SemaCXX/nested-name-spec.cpp
@@ -13,8 +13,8 @@ namespace A {
 }
 
 A:: ; // expected-error {{expected unqualified-id}}
-::A::ax::undef ex3; // expected-error {{no member named}} expected-error {{unknown type name 'undef'}}
-A::undef1::undef2 ex4; // expected-error {{no member named 'undef1'}} expected-error {{unknown type name 'undef2'}}
+::A::ax::undef ex3; // expected-error {{no member named}}
+A::undef1::undef2 ex4; // expected-error {{no member named 'undef1'}}
 
 int A::C::Ag1() { return 0; }
 
@@ -166,7 +166,7 @@ void N::f() { } // okay
 
 struct Y;  // expected-note{{forward declaration of 'struct Y'}}
 Y::foo y; // expected-error{{incomplete type 'struct Y' named in nested name specifier}} \
-         // expected-error{{unknown type name 'foo'}}
+         // expected-error{{no type named 'foo' in}}
 
 X::X() : a(5) { } // expected-error{{use of undeclared identifier 'X'}} \
       // expected-error{{C++ requires a type specifier for all declarations}} \
diff --git a/clang/test/SemaCXX/unknown-type-name.cpp b/clang/test/SemaCXX/unknown-type-name.cpp
new file mode 100644
index 00000000000..05421295133
--- /dev/null
+++ b/clang/test/SemaCXX/unknown-type-name.cpp
@@ -0,0 +1,29 @@
+// RUN: clang-cc -fsyntax-only -verify %s
+
+// PR3990
+namespace N {
+  struct Wibble {
+  };
+
+  typedef Wibble foo;
+}
+using namespace N;
+
+foo::bar x; // expected-error{{no type named 'bar' in 'struct N::Wibble'}}
+
+void f() {
+  foo::bar  = 4; // expected-error{{no member named 'bar' in 'struct N::Wibble'}}
+}
+
+template<typename T>
+struct A {
+  typedef T type;
+  
+  type f();
+};
+
+template<typename T>
+A<T>::type g(T t) { return t; } // expected-error{{missing 'typename'}}
+
+template<typename T>
+A<T>::type A<T>::f() { return type(); } // expected-error{{missing 'typename'}}
diff --git a/clang/test/SemaTemplate/instantiate-typedef.cpp b/clang/test/SemaTemplate/instantiate-typedef.cpp
index d30309cc86c..e092b531582 100644
--- a/clang/test/SemaTemplate/instantiate-typedef.cpp
+++ b/clang/test/SemaTemplate/instantiate-typedef.cpp
@@ -12,5 +12,5 @@ add_pointer<float>::type test2(int * ptr) {
 }
 
 add_pointer<int&>::type // expected-note{{in instantiation of template class 'struct add_pointer<int &>' requested here}} \
-// expected-error {{unknown type name 'type'}}
+// expected-error {{no type named 'type' in 'struct add_pointer<int &>'}}
 test3(); 
diff --git a/clang/test/SemaTemplate/typename-specifier.cpp b/clang/test/SemaTemplate/typename-specifier.cpp
index 62795eb0eee..2501b8d048f 100644
--- a/clang/test/SemaTemplate/typename-specifier.cpp
+++ b/clang/test/SemaTemplate/typename-specifier.cpp
@@ -43,12 +43,12 @@ namespace N {
 
 N::X<N::A>::type *ip4 = &i;
 N::X<N::B>::type *ip5 = &i; // expected-note{{in instantiation of template class 'struct N::X<struct N::B>' requested here}} \
-// expected-error{{unknown type name 'type'}}
+// expected-error{{no type named 'type' in}}
 N::X<N::C>::type *ip6 = &i; // expected-note{{in instantiation of template class 'struct N::X<struct N::C>' requested here}} \
-// expected-error{{unknown type name 'type'}}
+// expected-error{{no type named 'type' in}}
 
 N::X<int>::type fail1; // expected-note{{in instantiation of template class 'struct N::X<int>' requested here}} \
-// expected-error{{unknown type name 'type'}}
+// expected-error{{no type named 'type' in}}
 
 template<typename T>
 struct Y {
@@ -70,6 +70,6 @@ struct C {
 
 ::Y<A>::type ip7 = &i;
 ::Y<B>::type ip8 = &i; // expected-note{{in instantiation of template class 'struct Y<struct B>' requested here}} \
-// expected-error{{unknown type name 'type'}}
+// expected-error{{no type named 'type' in}}
 ::Y<C>::type ip9 = &i; // expected-note{{in instantiation of template class 'struct Y<struct C>' requested here}} \
-// expected-error{{unknown type name 'type'}}
+// expected-error{{no type named 'type' in}}