Author: rsmith
Date: Fri Sep 29 16:57:25 2017
New Revision: 314570
URL: http://llvm.org/viewvc/llvm-project?rev=314570&view=rev
Log:
Add a "vexing parse" warning for ambiguity between a variable declaration and a
function-style cast.
This fires for cases such as
T(x);
... where 'x' was previously declared and T is a type. This construct declares
a variable named 'x' rather than the (probably expected) interpretation of a
function-style cast of 'x' to T.
Modified:
cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
cfe/trunk/include/clang/Sema/DeclSpec.h
cfe/trunk/lib/Sema/SemaType.cpp
cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp
cfe/trunk/test/FixIt/fixit-vexing-parse.cpp
cfe/trunk/test/Parser/cxx0x-condition.cpp
cfe/trunk/test/Parser/cxx1z-class-template-argument-deduction.cpp
cfe/trunk/test/SemaCXX/decl-expr-ambiguity.cpp
Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=314570&r1=314569&r2=314570&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Fri Sep 29 16:57:25
2017
@@ -295,8 +295,20 @@ def warn_empty_parens_are_function_decl
def warn_parens_disambiguated_as_function_declaration : Warning<
"parentheses were disambiguated as a function declaration">,
InGroup<VexingParse>;
+def warn_parens_disambiguated_as_variable_declaration : Warning<
+ "parentheses were disambiguated as redundant parentheses around declaration "
+ "of variable named %0">, InGroup<VexingParse>;
+def warn_redundant_parens_around_declarator : Warning<
+ "redundant parentheses surrounding declarator">,
+ InGroup<DiagGroup<"redundant-parens">>, DefaultIgnore;
def note_additional_parens_for_variable_declaration : Note<
"add a pair of parentheses to declare a variable">;
+def note_raii_guard_add_name : Note<
+ "add a variable name to declare a %0 initialized with %1">;
+def note_function_style_cast_add_parentheses : Note<
+ "add enclosing parentheses to perform a function-style cast">;
+def note_remove_parens_for_variable_declaration : Note<
+ "remove parentheses to silence this warning">;
def note_empty_parens_function_call : Note<
"change this ',' to a ';' to call %0">;
def note_empty_parens_default_ctor : Note<
Modified: cfe/trunk/include/clang/Sema/DeclSpec.h
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/DeclSpec.h?rev=314570&r1=314569&r2=314570&view=diff
==============================================================================
--- cfe/trunk/include/clang/Sema/DeclSpec.h (original)
+++ cfe/trunk/include/clang/Sema/DeclSpec.h Fri Sep 29 16:57:25 2017
@@ -2301,6 +2301,42 @@ public:
}
llvm_unreachable("unknown context kind!");
}
+
+ /// Determine whether this declaration appears in a context where an
+ /// expression could appear.
+ bool isExpressionContext() const {
+ switch (Context) {
+ case FileContext:
+ case KNRTypeListContext:
+ case MemberContext:
+ case TypeNameContext: // FIXME: sizeof(...) permits an expression.
+ case FunctionalCastContext:
+ case AliasDeclContext:
+ case AliasTemplateContext:
+ case PrototypeContext:
+ case LambdaExprParameterContext:
+ case ObjCParameterContext:
+ case ObjCResultContext:
+ case TemplateParamContext:
+ case CXXNewContext:
+ case CXXCatchContext:
+ case ObjCCatchContext:
+ case BlockLiteralContext:
+ case LambdaExprContext:
+ case ConversionIdContext:
+ case TrailingReturnContext:
+ return false;
+
+ case BlockContext:
+ case ForContext:
+ case InitStmtContext:
+ case ConditionContext:
+ case TemplateTypeArgContext:
+ return true;
+ }
+
+ llvm_unreachable("unknown context kind!");
+ }
/// \brief Return true if a function declarator at this position would be a
/// function declaration.
Modified: cfe/trunk/lib/Sema/SemaType.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaType.cpp?rev=314570&r1=314569&r2=314570&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaType.cpp (original)
+++ cfe/trunk/lib/Sema/SemaType.cpp Fri Sep 29 16:57:25 2017
@@ -3065,6 +3065,7 @@ static void warnAboutAmbiguousFunction(S
S.Diag(D.getCommaLoc(), diag::note_empty_parens_function_call)
<< FixItHint::CreateReplacement(D.getCommaLoc(), ";")
<< D.getIdentifier();
+ Result.suppressDiagnostics();
}
}
@@ -3106,6 +3107,99 @@ static void warnAboutAmbiguousFunction(S
}
}
+/// Produce an appropriate diagnostic for a declarator with top-level
+/// parentheses.
+static void warnAboutRedundantParens(Sema &S, Declarator &D, QualType T) {
+ DeclaratorChunk &Paren = D.getTypeObject(D.getNumTypeObjects() - 1);
+ assert(Paren.Kind == DeclaratorChunk::Paren &&
+ "do not have redundant top-level parentheses");
+
+ // This is a syntactic check; we're not interested in cases that arise
+ // during template instantiation.
+ if (S.inTemplateInstantiation())
+ return;
+
+ // Check whether this could be intended to be a construction of a temporary
+ // object in C++ via a function-style cast.
+ bool CouldBeTemporaryObject =
+ S.getLangOpts().CPlusPlus && D.isExpressionContext() &&
+ !D.isInvalidType() && D.getIdentifier() &&
+ D.getDeclSpec().getParsedSpecifiers() == DeclSpec::PQ_TypeSpecifier &&
+ (T->isRecordType() || T->isDependentType()) &&
+ D.getDeclSpec().getTypeQualifiers() == 0 && D.isFirstDeclarator();
+
+ for (auto &C : D.type_objects()) {
+ switch (C.Kind) {
+ case DeclaratorChunk::Pointer:
+ case DeclaratorChunk::Paren:
+ continue;
+
+ case DeclaratorChunk::Array:
+ if (!C.Arr.NumElts)
+ CouldBeTemporaryObject = false;
+ continue;
+
+ case DeclaratorChunk::Reference:
+ // FIXME: Suppress the warning here if there is no initializer; we're
+ // going to give an error anyway.
+ // We assume that something like 'T (&x) = y;' is highly likely to not
+ // be intended to be a temporary object.
+ CouldBeTemporaryObject = false;
+ continue;
+
+ case DeclaratorChunk::Function:
+ // In a new-type-id, function chunks require parentheses.
+ if (D.getContext() == Declarator::CXXNewContext)
+ return;
+ LLVM_FALLTHROUGH;
+ case DeclaratorChunk::BlockPointer:
+ case DeclaratorChunk::MemberPointer:
+ case DeclaratorChunk::Pipe:
+ // These cannot appear in expressions.
+ CouldBeTemporaryObject = false;
+ continue;
+ }
+ }
+
+ // FIXME: If there is an initializer, assume that this is not intended to be
+ // a construction of a temporary object.
+
+ // Check whether the name has already been declared; if not, this is not a
+ // function-style cast.
+ if (CouldBeTemporaryObject) {
+ LookupResult Result(S, D.getIdentifier(), SourceLocation(),
+ Sema::LookupOrdinaryName);
+ if (!S.LookupName(Result, S.getCurScope()))
+ CouldBeTemporaryObject = false;
+ Result.suppressDiagnostics();
+ }
+
+ SourceRange ParenRange(Paren.Loc, Paren.EndLoc);
+
+ if (!CouldBeTemporaryObject) {
+ S.Diag(Paren.Loc, diag::warn_redundant_parens_around_declarator)
+ << ParenRange << FixItHint::CreateRemoval(Paren.Loc)
+ << FixItHint::CreateRemoval(Paren.EndLoc);
+ return;
+ }
+
+ S.Diag(Paren.Loc, diag::warn_parens_disambiguated_as_variable_declaration)
+ << ParenRange << D.getIdentifier();
+ auto *RD = T->getAsCXXRecordDecl();
+ if (!RD || !RD->hasDefinition() || RD->hasNonTrivialDestructor())
+ S.Diag(Paren.Loc, diag::note_raii_guard_add_name)
+ << FixItHint::CreateInsertion(Paren.Loc, " varname") << T
+ << D.getIdentifier();
+ // FIXME: A cast to void is probably a better suggestion in cases where it's
+ // valid (when there is no initializer and we're not in a condition).
+ S.Diag(D.getLocStart(), diag::note_function_style_cast_add_parentheses)
+ << FixItHint::CreateInsertion(D.getLocStart(), "(")
+ << FixItHint::CreateInsertion(S.getLocForEndOfToken(D.getLocEnd()), ")");
+ S.Diag(Paren.Loc, diag::note_remove_parens_for_variable_declaration)
+ << FixItHint::CreateRemoval(Paren.Loc)
+ << FixItHint::CreateRemoval(Paren.EndLoc);
+}
+
/// Helper for figuring out the default CC for a function declarator type. If
/// this is the outermost chunk, then we can determine the CC from the
/// declarator context. If not, then this could be either a member function
@@ -4007,6 +4101,8 @@ static TypeSourceInfo *GetFullTypeForDec
IsQualifiedFunction &= DeclType.Kind == DeclaratorChunk::Paren;
switch (DeclType.Kind) {
case DeclaratorChunk::Paren:
+ if (i == 0)
+ warnAboutRedundantParens(S, D, T);
T = S.BuildParenType(T);
break;
case DeclaratorChunk::BlockPointer:
Modified:
cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp?rev=314570&r1=314569&r2=314570&view=diff
==============================================================================
--- cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp
(original)
+++ cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.qual/class.qual/p2.cpp
Fri Sep 29 16:57:25 2017
@@ -73,6 +73,7 @@ void other_contexts() {
int a;
{
X0::X0(a); // expected-error{{qualified reference to 'X0' is a constructor
name rather than a type in this context}}
+ // expected-warning@-1 {{redundant parentheses around declaration of
variable named 'a'}} expected-note@-1 2{{}}
}
}
Modified: cfe/trunk/test/FixIt/fixit-vexing-parse.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/FixIt/fixit-vexing-parse.cpp?rev=314570&r1=314569&r2=314570&view=diff
==============================================================================
--- cfe/trunk/test/FixIt/fixit-vexing-parse.cpp (original)
+++ cfe/trunk/test/FixIt/fixit-vexing-parse.cpp Fri Sep 29 16:57:25 2017
@@ -106,3 +106,24 @@ namespace N {
wchar_t wc(); // expected-warning {{function declaration}} expected-note
{{replace parentheses with an initializer}}
}
}
+
+namespace RedundantParens {
+struct Y {
+ Y();
+ Y(int);
+ ~Y();
+};
+int n;
+
+void test() {
+ // CHECK: add a variable name
+ // CHECK: fix-it:"{{.*}}":{[[@LINE+7]]:4-[[@LINE+7]]:4}:" varname"
+ // CHECK: add enclosing parentheses
+ // CHECK: fix-it:"{{.*}}":{[[@LINE+5]]:3-[[@LINE+5]]:3}:"("
+ // CHECK: fix-it:"{{.*}}":{[[@LINE+4]]:7-[[@LINE+4]]:7}:")"
+ // CHECK: remove parentheses
+ // CHECK: fix-it:"{{.*}}":{[[@LINE+2]]:4-[[@LINE+2]]:5}:" "
+ // CHECK: fix-it:"{{.*}}":{[[@LINE+1]]:6-[[@LINE+1]]:7}:""
+ Y(n); // expected-warning {{declaration of variable named 'n'}}
expected-note 3{{}}
+}
+}
Modified: cfe/trunk/test/Parser/cxx0x-condition.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx0x-condition.cpp?rev=314570&r1=314569&r2=314570&view=diff
==============================================================================
--- cfe/trunk/test/Parser/cxx0x-condition.cpp (original)
+++ cfe/trunk/test/Parser/cxx0x-condition.cpp Fri Sep 29 16:57:25 2017
@@ -14,11 +14,11 @@ void f() {
for (; int x = ++a; ) ;
if (S(a)) {} // ok
- if (S(a) = 0) {} // ok
+ if (S(a) = 0) {} // expected-warning {{redundant parentheses}} expected-note
2{{}}
if (S(a) == 0) {} // ok
if (S(n)) {} // expected-error {{unexpected type name 'n': expected
expression}}
- if (S(n) = 0) {} // ok
+ if (S(n) = 0) {} // expected-warning {{redundant parentheses}} expected-note
2{{}}
if (S(n) == 0) {} // expected-error {{unexpected type name 'n': expected
expression}}
if (S b(a)) {} // expected-error {{variable declaration in condition cannot
have a parenthesized initializer}}
Modified: cfe/trunk/test/Parser/cxx1z-class-template-argument-deduction.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx1z-class-template-argument-deduction.cpp?rev=314570&r1=314569&r2=314570&view=diff
==============================================================================
--- cfe/trunk/test/Parser/cxx1z-class-template-argument-deduction.cpp (original)
+++ cfe/trunk/test/Parser/cxx1z-class-template-argument-deduction.cpp Fri Sep
29 16:57:25 2017
@@ -180,6 +180,7 @@ namespace typename_specifier {
{(void)(typename T::A)(0);} // expected-error{{refers to class template
member}}
{(void)(typename T::A){0};} // expected-error{{refers to class template
member}}
{typename T::A (parens) = 0;} // expected-error {{refers to class template
member in 'typename_specifier::X'; argument deduction not allowed here}}
+ // expected-warning@-1 {{disambiguated as redundant parentheses around
declaration of variable named 'parens'}} expected-note@-1 {{add a variable
name}} expected-note@-1{{remove parentheses}} expected-note@-1 {{add enclosing
parentheses}}
{typename T::A *p = 0;} // expected-error {{refers to class template
member}}
{typename T::A &r = *p;} // expected-error {{refers to class template
member}}
{typename T::A arr[3] = 0;} // expected-error {{refers to class template
member}}
Modified: cfe/trunk/test/SemaCXX/decl-expr-ambiguity.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/decl-expr-ambiguity.cpp?rev=314570&r1=314569&r2=314570&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/decl-expr-ambiguity.cpp (original)
+++ cfe/trunk/test/SemaCXX/decl-expr-ambiguity.cpp Fri Sep 29 16:57:25 2017
@@ -48,13 +48,20 @@ void f() {
struct RAII {
RAII();
+ RAII(int);
~RAII();
};
+struct NotRAII {
+ NotRAII();
+ NotRAII(int);
+};
+
void func();
void func2(short);
namespace N {
struct S;
+ int n;
void emptyParens() {
RAII raii(); // expected-warning {{function declaration}} expected-note
{{remove parentheses to declare a variable}}
@@ -69,6 +76,23 @@ namespace N {
void nonEmptyParens() {
int f = 0, // g = 0; expected-note {{change this ',' to a ';' to call
'func2'}}
func2(short(f)); // expected-warning {{function declaration}}
expected-note {{add a pair of parentheses}}
+
+ RAII(n); // expected-warning {{parentheses were disambiguated as redundant
parentheses around declaration of variable named 'n'}}
+ // expected-note@-1 {{add a variable name to declare a 'RAII' initialized
with 'n'}}
+ // expected-note@-2 {{add enclosing parentheses to perform a
function-style cast}}
+ // expected-note@-3 {{remove parentheses to silence this warning}}
+
+ RAII(undeclared1);
+#pragma clang diagnostic push
+#pragma clang diagnostic warning "-Wredundant-parens"
+ RAII(undeclared2); // expected-warning {{redundant parentheses surrounding
declarator}}
+#pragma clang diagnostic pop
+
+ {
+ NotRAII(n); // expected-warning {{parentheses were disambiguated as
redundant parentheses around declaration of variable named 'n'}}
+ // expected-note@-1 {{add enclosing parentheses to perform a
function-style cast}}
+ // expected-note@-2 {{remove parentheses to silence this warning}}
+ }
}
}
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