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Improve parser recovery when we encounter a dependent template name 

that is missing the 'template' keyword, e.g., 

  t->getAs<T>()

where getAs is a member of an unknown specialization. C++ requires
that we treat "getAs" as a value, but that would fail to parse since T
is the name of a type. We would then fail at the '>', since a type
cannot be followed by a '>'.

This is a very common error for C++ programmers to make, especially
since GCC occasionally allows it when it shouldn't (as does Visual
C++). So, when we are in this case, we use tentative parsing to see if
the tokens starting at "<" can only be parsed as a template argument
list. If so, we produce a diagnostic with a fix-it that states that
the 'template' keyword is needed:

test/SemaTemplate/dependent-template-recover.cpp:5:8: error: 'template' keyword
      is required to treat 'getAs' as a dependent template name
    t->getAs<T>();
       ^
       template 

This is just a start of this patch; I'd like to apply the same
approach to everywhere that a template-id with dependent template name
can be parsed.

llvm-svn: 104406
This commit is contained in:
Douglas Gregor 2010-05-21 23:18:07 +00:00
parent 4dc833c607
commit 786123dc48
12 changed files with 128 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
clang/include/clang/Basic/DiagnosticParseKinds.td
View File

@ -313,6 +313,9 @@ def err_explicit_instantiation_with_definition : Error<
"'template' keyword">;
def err_enum_template : Error<"enumeration cannot be a template">;
def err_missing_dependent_template_keyword : Error<
"use 'template' keyword to treat '%0' as a dependent template name">;
// Constructor template diagnostics.
def err_out_of_line_constructor_template_id : Error<
"out-of-line constructor for %0 cannot have template arguments">;

11
clang/include/clang/Parse/Action.h
View File

@ -286,13 +286,18 @@ public:
/// \param Template if the name does refer to a template, the declaration
/// of the template that the name refers to.
///
/// \param MemberOfUnknownSpecialization Will be set true if the resulting
/// member would be a member of an unknown specialization, in which case this
/// lookup cannot possibly pass at this time.
///
/// \returns the kind of template that this name refers to.
virtual TemplateNameKind isTemplateName(Scope *S,
CXXScopeSpec &SS,
UnqualifiedId &Name,
TypeTy *ObjectType,
bool EnteringContext,
TemplateTy &Template) = 0;
TemplateTy &Template,
bool &MemberOfUnknownSpecialization) = 0;
/// \brief Action called as part of error recovery when the parser has
/// determined that the given name must refer to a template, but
@ -3027,7 +3032,9 @@ public:
UnqualifiedId &Name,
TypeTy *ObjectType,
bool EnteringContext,
TemplateTy &Template);
TemplateTy &Template,
bool &MemberOfUnknownSpecialization);
/// ActOnDeclarator - If this is a typedef declarator, we modify the
/// IdentifierInfo::FETokenInfo field to keep track of this fact, until S is

1
clang/include/clang/Parse/Parser.h
View File

@ -1463,6 +1463,7 @@ private:
SourceLocation TemplateKWLoc = SourceLocation(),
bool AllowTypeAnnotation = true);
void AnnotateTemplateIdTokenAsType(const CXXScopeSpec *SS = 0);
bool IsTemplateArgumentList();
bool ParseTemplateArgumentList(TemplateArgList &TemplateArgs);
ParsedTemplateArgument ParseTemplateTemplateArgument();
ParsedTemplateArgument ParseTemplateArgument();

4
clang/lib/Parse/MinimalAction.cpp
View File

@ -194,7 +194,9 @@ MinimalAction::isTemplateName(Scope *S,
UnqualifiedId &Name,
TypeTy *ObjectType,
bool EnteringScope,
TemplateTy &TemplateDecl) {
TemplateTy &TemplateDecl,
bool &MemberOfUnknownSpecialization) {
MemberOfUnknownSpecialization = false;
return TNK_Non_template;
}

46
clang/lib/Parse/ParseExprCXX.cpp
View File

@ -289,11 +289,13 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
TemplateTy Template;
UnqualifiedId TemplateName;
TemplateName.setIdentifier(&II, Tok.getLocation());
bool MemberOfUnknownSpecialization;
if (TemplateNameKind TNK = Actions.isTemplateName(CurScope, SS,
TemplateName,
ObjectType,
EnteringContext,
Template)) {
Template,
MemberOfUnknownSpecialization)) {
// We have found a template name, so annotate this this token
// with a template-id annotation. We do not permit the
// template-id to be translated into a type annotation,
@ -990,21 +992,54 @@ bool Parser::ParseUnqualifiedIdTemplateId(CXXScopeSpec &SS,
TNK = TNK_Dependent_template_name;
if (!Template.get())
return true;
} else
} else {
bool MemberOfUnknownSpecialization;
TNK = Actions.isTemplateName(CurScope, SS, Id, ObjectType,
EnteringContext, Template);
EnteringContext, Template,
MemberOfUnknownSpecialization);
if (TNK == TNK_Non_template && MemberOfUnknownSpecialization &&
ObjectType && IsTemplateArgumentList()) {
// We have something like t->getAs<T>(), where getAs is a
// member of an unknown specialization. However, this will only
// parse correctly as a template, so suggest the keyword 'template'
// before 'getAs' and treat this as a dependent template name.
std::string Name;
if (Id.getKind() == UnqualifiedId::IK_Identifier)
Name = Id.Identifier->getName();
else {
Name = "operator ";
if (Id.getKind() == UnqualifiedId::IK_OperatorFunctionId)
Name += getOperatorSpelling(Id.OperatorFunctionId.Operator);
else
Name += Id.Identifier->getName();
}
Diag(Id.StartLocation, diag::err_missing_dependent_template_keyword)
<< Name
<< FixItHint::CreateInsertion(Id.StartLocation, "template ");
Template = Actions.ActOnDependentTemplateName(TemplateKWLoc, SS,
Id, ObjectType,
EnteringContext);
TNK = TNK_Dependent_template_name;
if (!Template.get())
return true;
}
}
break;
case UnqualifiedId::IK_ConstructorName: {
UnqualifiedId TemplateName;
bool MemberOfUnknownSpecialization;
TemplateName.setIdentifier(Name, NameLoc);
TNK = Actions.isTemplateName(CurScope, SS, TemplateName, ObjectType,
EnteringContext, Template);
EnteringContext, Template,
MemberOfUnknownSpecialization);
break;
}
case UnqualifiedId::IK_DestructorName: {
UnqualifiedId TemplateName;
bool MemberOfUnknownSpecialization;
TemplateName.setIdentifier(Name, NameLoc);
if (ObjectType) {
Template = Actions.ActOnDependentTemplateName(TemplateKWLoc, SS,
@ -1015,7 +1050,8 @@ bool Parser::ParseUnqualifiedIdTemplateId(CXXScopeSpec &SS,
return true;
} else {
TNK = Actions.isTemplateName(CurScope, SS, TemplateName, ObjectType,
EnteringContext, Template);
EnteringContext, Template,
MemberOfUnknownSpecialization);
if (TNK == TNK_Non_template && Id.DestructorName == 0) {
Diag(NameLoc, diag::err_destructor_template_id)

30
clang/lib/Parse/ParseTemplate.cpp
View File

@ -902,10 +902,12 @@ ParsedTemplateArgument Parser::ParseTemplateTemplateArgument() {
ConsumeToken(); // the identifier
if (isEndOfTemplateArgument(Tok)) {
bool MemberOfUnknownSpecialization;
TemplateNameKind TNK = Actions.isTemplateName(CurScope, SS, Name,
/*ObjectType=*/0,
/*EnteringContext=*/false,
Template);
Template,
MemberOfUnknownSpecialization);
if (TNK == TNK_Dependent_template_name || TNK == TNK_Type_template) {
// We have an id-expression that refers to a class template or
// (C++0x) template alias.
@ -966,6 +968,32 @@ ParsedTemplateArgument Parser::ParseTemplateArgument() {
ExprArg.release(), Loc);
}
/// \brief Determine whether the current tokens can only be parsed as a
/// template argument list (starting with the '<') and never as a '<'
/// expression.
bool Parser::IsTemplateArgumentList() {
struct AlwaysRevertAction : TentativeParsingAction {
AlwaysRevertAction(Parser &P) : TentativeParsingAction(P) { }
~AlwaysRevertAction() { Revert(); }
} Tentative(*this);
// '<'
if (!Tok.is(tok::less))
return false;
ConsumeToken();
// An empty template argument list.
if (Tok.is(tok::greater))
return true;
// See whether we have declaration specifiers, which indicate a type.
while (isCXXDeclarationSpecifier() == TPResult::True())
ConsumeToken();
// If we have a '>' or a ',' then this is a template argument list.
return Tok.is(tok::greater) || Tok.is(tok::comma);
}
/// ParseTemplateArgumentList - Parse a C++ template-argument-list
/// (C++ [temp.names]). Returns true if there was an error.
///

3
clang/lib/Parse/Parser.cpp
View File

@ -980,10 +980,11 @@ bool Parser::TryAnnotateTypeOrScopeToken(bool EnteringContext) {
TemplateTy Template;
UnqualifiedId TemplateName;
TemplateName.setIdentifier(Tok.getIdentifierInfo(), Tok.getLocation());
bool MemberOfUnknownSpecialization;
if (TemplateNameKind TNK
= Actions.isTemplateName(CurScope, SS, TemplateName,
/*ObjectType=*/0, EnteringContext,
Template)) {
Template, MemberOfUnknownSpecialization)) {
// Consume the identifier.
ConsumeToken();
if (AnnotateTemplateIdToken(Template, TNK, &SS, TemplateName)) {

6
clang/lib/Sema/Sema.h
View File

@ -2800,14 +2800,16 @@ public:
// C++ Templates [C++ 14]
//
void LookupTemplateName(LookupResult &R, Scope *S, CXXScopeSpec &SS,
QualType ObjectType, bool EnteringContext);
QualType ObjectType, bool EnteringContext,
bool &MemberOfUnknownSpecialization);
virtual TemplateNameKind isTemplateName(Scope *S,
CXXScopeSpec &SS,
UnqualifiedId &Name,
TypeTy *ObjectType,
bool EnteringContext,
TemplateTy &Template);
TemplateTy &Template,
bool &MemberOfUnknownSpecialization);
virtual bool DiagnoseUnknownTemplateName(const IdentifierInfo &II,
SourceLocation IILoc,

5
clang/lib/Sema/SemaDecl.cpp
View File

@ -287,8 +287,9 @@ bool Sema::DiagnoseUnknownTypeName(const IdentifierInfo &II,
Name.setIdentifier(&II, IILoc);
CXXScopeSpec EmptySS;
TemplateTy TemplateResult;
if (isTemplateName(S, SS ? *SS : EmptySS, Name, 0, true, TemplateResult)
== TNK_Type_template) {
bool MemberOfUnknownSpecialization;
if (isTemplateName(S, SS ? *SS : EmptySS, Name, 0, true, TemplateResult,
MemberOfUnknownSpecialization) == TNK_Type_template) {
TemplateName TplName = TemplateResult.getAsVal<TemplateName>();
Diag(IILoc, diag::err_template_missing_args) << TplName;
if (TemplateDecl *TplDecl = TplName.getAsTemplateDecl()) {

4
clang/lib/Sema/SemaExpr.cpp
View File

@ -1055,7 +1055,9 @@ Sema::OwningExprResult Sema::ActOnIdExpression(Scope *S,
// lookup to determine that it was a template name in the first place. If
// this becomes a performance hit, we can work harder to preserve those
// results until we get here but it's likely not worth it.
LookupTemplateName(R, S, SS, QualType(), /*EnteringContext=*/false);
bool MemberOfUnknownSpecialization;
LookupTemplateName(R, S, SS, QualType(), /*EnteringContext=*/false,
MemberOfUnknownSpecialization);
} else {
bool IvarLookupFollowUp = (!SS.isSet() && II && getCurMethodDecl());
LookupParsedName(R, S, &SS, !IvarLookupFollowUp);

20
clang/lib/Sema/SemaTemplate.cpp
View File

@ -100,10 +100,12 @@ TemplateNameKind Sema::isTemplateName(Scope *S,
UnqualifiedId &Name,
TypeTy *ObjectTypePtr,
bool EnteringContext,
TemplateTy &TemplateResult) {
TemplateTy &TemplateResult,
bool &MemberOfUnknownSpecialization) {
assert(getLangOptions().CPlusPlus && "No template names in C!");
DeclarationName TName;
MemberOfUnknownSpecialization = false;
switch (Name.getKind()) {
case UnqualifiedId::IK_Identifier:
@ -128,7 +130,8 @@ TemplateNameKind Sema::isTemplateName(Scope *S,
LookupResult R(*this, TName, Name.getSourceRange().getBegin(),
LookupOrdinaryName);
R.suppressDiagnostics();
LookupTemplateName(R, S, SS, ObjectType, EnteringContext);
LookupTemplateName(R, S, SS, ObjectType, EnteringContext,
MemberOfUnknownSpecialization);
if (R.empty() || R.isAmbiguous())
return TNK_Non_template;
@ -191,8 +194,10 @@ bool Sema::DiagnoseUnknownTemplateName(const IdentifierInfo &II,
void Sema::LookupTemplateName(LookupResult &Found,
Scope *S, CXXScopeSpec &SS,
QualType ObjectType,
bool EnteringContext) {
bool EnteringContext,
bool &MemberOfUnknownSpecialization) {
// Determine where to perform name lookup
MemberOfUnknownSpecialization = false;
DeclContext *LookupCtx = 0;
bool isDependent = false;
if (!ObjectType.isNull()) {
@ -241,6 +246,7 @@ void Sema::LookupTemplateName(LookupResult &Found,
} else if (isDependent) {
// We cannot look into a dependent object type or nested nme
// specifier.
MemberOfUnknownSpecialization = true;
return;
} else {
// Perform unqualified name lookup in the current scope.
@ -1641,8 +1647,10 @@ Sema::BuildQualifiedTemplateIdExpr(CXXScopeSpec &SS,
RequireCompleteDeclContext(SS, DC))
return BuildDependentDeclRefExpr(SS, Name, NameLoc, &TemplateArgs);
bool MemberOfUnknownSpecialization;
LookupResult R(*this, Name, NameLoc, LookupOrdinaryName);
LookupTemplateName(R, (Scope*) 0, SS, QualType(), /*Entering*/ false);
LookupTemplateName(R, (Scope*) 0, SS, QualType(), /*Entering*/ false,
MemberOfUnknownSpecialization);
if (R.isAmbiguous())
return ExprError();
@ -1699,8 +1707,10 @@ Sema::ActOnDependentTemplateName(SourceLocation TemplateKWLoc,
// "template" keyword is now permitted). We follow the C++0x
// rules, even in C++03 mode, retroactively applying the DR.
TemplateTy Template;
bool MemberOfUnknownSpecialization;
TemplateNameKind TNK = isTemplateName(0, SS, Name, ObjectType,
EnteringContext, Template);
EnteringContext, Template,
MemberOfUnknownSpecialization);
if (TNK == TNK_Non_template && LookupCtx->isDependentContext() &&
isa<CXXRecordDecl>(LookupCtx) &&
cast<CXXRecordDecl>(LookupCtx)->hasAnyDependentBases()) {

15
clang/test/SemaTemplate/dependent-template-recover.cpp Normal file
View File

@ -0,0 +1,15 @@
// RUN: %clang_cc1 -fsyntax-only -verify %s
template<typename T, typename U, int N>
struct X {
void f(T* t) {
t->f0<U>(); // expected-error{{use 'template' keyword to treat 'f0' as a dependent template name}}
t->f0<int>(); // expected-error{{use 'template' keyword to treat 'f0' as a dependent template name}}
t->operator+<U const, 1>(); // expected-error{{use 'template' keyword to treat 'operator +' as a dependent template name}}
t->f1<int const, 2>(); // expected-error{{use 'template' keyword to treat 'f1' as a dependent template name}}
// FIXME: We can't recover from these yet
(*t).f2<N>(); // expected-error{{expected expression}}
(*t).f2<0>(); // expected-error{{expected expression}}
}
};