Hi rsmith, faisalv, fraggamuffin,
This change implements parse-only acceptance of the optional
requires-clause in a template-declaration. Diagnostic testing is added
for cases where the grammar is ambiguous with the expectation that the
longest token sequence which matches the syntax of a
constraint-expression is consumed without backtracking.
http://reviews.llvm.org/D10462
Files:
include/clang/Parse/Parser.h
lib/Parse/ParseExpr.cpp
lib/Parse/ParseTemplate.cpp
test/Parser/cxx-concepts-ambig-constraint-expr.cpp
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Index: include/clang/Parse/Parser.h
===================================================================
--- include/clang/Parse/Parser.h
+++ include/clang/Parse/Parser.h
@@ -1314,6 +1314,7 @@
ExprResult ParseExpression(TypeCastState isTypeCast = NotTypeCast);
ExprResult ParseConstantExpression(TypeCastState isTypeCast = NotTypeCast);
+ ExprResult ParseConstraintExpression();
// Expr that doesn't include commas.
ExprResult ParseAssignmentExpression(TypeCastState isTypeCast = NotTypeCast);
Index: lib/Parse/ParseExpr.cpp
===================================================================
--- lib/Parse/ParseExpr.cpp
+++ lib/Parse/ParseExpr.cpp
@@ -205,6 +205,24 @@
return Actions.ActOnConstantExpression(Res);
}
+/// \brief Parse a constraint-expression.
+///
+/// \verbatim
+/// constraint-expression: [Concepts TS temp.constr.decl p1]
+/// logical-or-expression
+/// \endverbatim
+ExprResult Parser::ParseConstraintExpression() {
+ // FIXME: this may erroneously consume a function-body as the braced
+ // initializer list of a compound literal
+ //
+ // FIXME: this may erroneously consume a parenthesized rvalue reference
+ // declarator as a parenthesized address-of-label expression
+ ExprResult LHS(ParseCastExpression(/*isUnaryExpression=*/false));
+ ExprResult Res(ParseRHSOfBinaryExpression(LHS, prec::LogicalOr));
+
+ return Res;
+}
+
bool Parser::isNotExpressionStart() {
tok::TokenKind K = Tok.getKind();
if (K == tok::l_brace || K == tok::r_brace ||
Index: lib/Parse/ParseTemplate.cpp
===================================================================
--- lib/Parse/ParseTemplate.cpp
+++ lib/Parse/ParseTemplate.cpp
@@ -116,7 +116,7 @@
SmallVector<Decl*, 4> TemplateParams;
if (ParseTemplateParameters(CurTemplateDepthTracker.getDepth(),
TemplateParams, LAngleLoc, RAngleLoc)) {
- // Skip until the semi-colon or a }.
+ // Skip until the semi-colon or a '}'.
SkipUntil(tok::r_brace, StopAtSemi | StopBeforeMatch);
TryConsumeToken(tok::semi);
return nullptr;
@@ -132,6 +132,17 @@
if (!TemplateParams.empty()) {
isSpecialization = false;
++CurTemplateDepthTracker;
+
+ if (TryConsumeToken(tok::kw_requires)) {
+ ExprResult ER =
+ Actions.CorrectDelayedTyposInExpr(ParseConstraintExpression());
+ if (!ER.isUsable()) {
+ // Skip until the semi-colon or a '}'.
+ SkipUntil(tok::r_brace, StopAtSemi | StopBeforeMatch);
+ TryConsumeToken(tok::semi);
+ return nullptr;
+ }
+ }
} else {
LastParamListWasEmpty = true;
}
Index: test/Parser/cxx-concepts-ambig-constraint-expr.cpp
===================================================================
--- /dev/null
+++ test/Parser/cxx-concepts-ambig-constraint-expr.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -std=c++14 -fconcepts-ts -x c++ %s -verify
+
+/******************************************************************************
+ * Test parsing of constraint-expressions in cases where the grammar is
+ * ambiguous with the expectation that the longest token sequence which matches
+ * the syntax is consumed without backtracking.
+ ******************************************************************************/
+
+// type-specifier-seq in conversion-type-id
+template <typename T> requires (bool)&T::operator short
+unsigned int foo(); // expected-error {{C++ requires a type specifier for all declarations}}
+
+// type-specifier-seq in new-type-id
+template <typename T> requires (bool)sizeof new (T::f()) short
+unsigned int bar(); // expected-error {{C++ requires a type specifier for all declarations}}
+
+template<typename T> requires (bool)sizeof new (T::f()) unsigned // expected-error {{'struct' cannot be signed or unsigned}}
+struct X { }; // expected-error {{'X' cannot be defined in a type specifier}}
+
+// C-style cast
+// of function call on function-style cast
+template <typename T> requires (bool(T()))
+T (*fp)(); // expected-error {{use of undeclared identifier 'fp'}}
+
+// function-style cast
+// as the callee in a function call
+struct A {
+ static int t;
+ template <typename T> requires bool(T())
+ (A(T (&t))) { } // expected-error {{called object type 'bool' is not a function or function pointer}}
+};
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