rymiel created this revision.
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Since P0857, part of C++20, a *lambda-expression* can contain a
*requires-clause* after its *template-parameter-list*.
While support for this was added as part of
eccc734a69c0c012ae3160887b65a535b35ead3e
<https://reviews.llvm.org/rGeccc734a69c0c012ae3160887b65a535b35ead3e>, one
specific case isn't
handled properly, where the *requires-clause* consists of an
instantiation of a boolean variable template. This is due to a
diagnostic check which was written with the assumption that a
*requires-clause* can never be followed by a left parenthesis. This
assumption no longer holds for lambdas.
This diagnostic check would then attempt to perform a "recovery", but it
does so in a valid parse state, resulting in an invalid parse state
instead!
This patch adds a special case when parsing requires clauses of lambda
templates, to skip this diagnostic check.
Fixes https://github.com/llvm/llvm-project/issues/61278
Fixes https://github.com/llvm/llvm-project/issues/61387
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D146140
Files:
clang/include/clang/Parse/Parser.h
clang/include/clang/Sema/Sema.h
clang/lib/Parse/ParseExpr.cpp
clang/lib/Parse/ParseExprCXX.cpp
clang/lib/Sema/SemaConcept.cpp
clang/test/SemaTemplate/concepts.cpp
Index: clang/test/SemaTemplate/concepts.cpp
===================================================================
--- clang/test/SemaTemplate/concepts.cpp
+++ clang/test/SemaTemplate/concepts.cpp
@@ -55,10 +55,15 @@
}
namespace P0857R0 {
+ template <typename T> static constexpr bool V = true;
+
void f() {
auto x = []<bool B> requires B {}; // expected-note {{constraints not satisfied}} expected-note {{false}}
x.operator()<true>();
x.operator()<false>(); // expected-error {{no matching member function}}
+
+ auto y = []<typename T> requires V<T> () {};
+ y.operator()<int>(); // OK
}
template<typename T> concept C = true;
Index: clang/lib/Sema/SemaConcept.cpp
===================================================================
--- clang/lib/Sema/SemaConcept.cpp
+++ clang/lib/Sema/SemaConcept.cpp
@@ -87,7 +87,8 @@
bool Sema::CheckConstraintExpression(const Expr *ConstraintExpression,
Token NextToken, bool *PossibleNonPrimary,
- bool IsTrailingRequiresClause) {
+ bool IsTrailingRequiresClause,
+ bool IsLambdaRequiresClause) {
// C++2a [temp.constr.atomic]p1
// ..E shall be a constant expression of type bool.
@@ -112,7 +113,7 @@
// The user probably isn't aware of the parentheses required around
// the function call, and we're only going to parse 'func' as the
// primary-expression, and complain that it is of non-bool type.
- (NextToken.is(tok::l_paren) &&
+ (NextToken.is(tok::l_paren) && !IsLambdaRequiresClause &&
(IsTrailingRequiresClause ||
(Type->isDependentType() &&
isa<UnresolvedLookupExpr>(ConstraintExpression)) ||
Index: clang/lib/Parse/ParseExprCXX.cpp
===================================================================
--- clang/lib/Parse/ParseExprCXX.cpp
+++ clang/lib/Parse/ParseExprCXX.cpp
@@ -1345,7 +1345,8 @@
if (TryConsumeToken(tok::kw_requires)) {
RequiresClause =
Actions.ActOnRequiresClause(ParseConstraintLogicalOrExpression(
- /*IsTrailingRequiresClause=*/false));
+ /*IsTrailingRequiresClause=*/false,
+ /*IsLambdaRequiresClause=*/true));
if (RequiresClause.isInvalid())
SkipUntil({tok::l_brace, tok::l_paren}, StopAtSemi | StopBeforeMatch);
}
Index: clang/lib/Parse/ParseExpr.cpp
===================================================================
--- clang/lib/Parse/ParseExpr.cpp
+++ clang/lib/Parse/ParseExpr.cpp
@@ -255,7 +255,8 @@
///
/// \endverbatim
ExprResult
-Parser::ParseConstraintLogicalAndExpression(bool IsTrailingRequiresClause) {
+Parser::ParseConstraintLogicalAndExpression(bool IsTrailingRequiresClause,
+ bool IsLambdaRequiresClause) {
EnterExpressionEvaluationContext ConstantEvaluated(
Actions, Sema::ExpressionEvaluationContext::Unevaluated);
bool NotPrimaryExpression = false;
@@ -299,9 +300,9 @@
NotPrimaryExpression = false;
}
bool PossibleNonPrimary;
- bool IsConstraintExpr =
- Actions.CheckConstraintExpression(E.get(), Tok, &PossibleNonPrimary,
- IsTrailingRequiresClause);
+ bool IsConstraintExpr = Actions.CheckConstraintExpression(
+ E.get(), Tok, &PossibleNonPrimary, IsTrailingRequiresClause,
+ IsLambdaRequiresClause);
if (!IsConstraintExpr || PossibleNonPrimary) {
// Atomic constraint might be an unparenthesized non-primary expression
// (such as a binary operator), in which case we might get here (e.g. in
@@ -347,14 +348,16 @@
///
/// \endverbatim
ExprResult
-Parser::ParseConstraintLogicalOrExpression(bool IsTrailingRequiresClause) {
- ExprResult LHS(ParseConstraintLogicalAndExpression(IsTrailingRequiresClause));
+Parser::ParseConstraintLogicalOrExpression(bool IsTrailingRequiresClause,
+ bool IsLambdaRequiresClause) {
+ ExprResult LHS(ParseConstraintLogicalAndExpression(IsTrailingRequiresClause,
+ IsLambdaRequiresClause));
if (!LHS.isUsable())
return ExprError();
while (Tok.is(tok::pipepipe)) {
SourceLocation LogicalOrLoc = ConsumeToken();
- ExprResult RHS =
- ParseConstraintLogicalAndExpression(IsTrailingRequiresClause);
+ ExprResult RHS = ParseConstraintLogicalAndExpression(
+ IsTrailingRequiresClause, IsLambdaRequiresClause);
if (!RHS.isUsable()) {
Actions.CorrectDelayedTyposInExpr(LHS);
return ExprError();
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -7253,7 +7253,8 @@
/// non-primary expression being used as an atomic constraint.
bool CheckConstraintExpression(const Expr *CE, Token NextToken = Token(),
bool *PossibleNonPrimary = nullptr,
- bool IsTrailingRequiresClause = false);
+ bool IsTrailingRequiresClause = false,
+ bool IsLambdaRequiresClause = false);
private:
/// Caches pairs of template-like decls whose associated constraints were
Index: clang/include/clang/Parse/Parser.h
===================================================================
--- clang/include/clang/Parse/Parser.h
+++ clang/include/clang/Parse/Parser.h
@@ -1776,8 +1776,11 @@
ExprResult ParseCaseExpression(SourceLocation CaseLoc);
ExprResult ParseConstraintExpression();
ExprResult
- ParseConstraintLogicalAndExpression(bool IsTrailingRequiresClause);
- ExprResult ParseConstraintLogicalOrExpression(bool IsTrailingRequiresClause);
+ ParseConstraintLogicalAndExpression(bool IsTrailingRequiresClause,
+ bool IsLambdaRequiresClause = false);
+ ExprResult
+ ParseConstraintLogicalOrExpression(bool IsTrailingRequiresClause,
+ bool IsLambdaRequiresClause = false);
// Expr that doesn't include commas.
ExprResult ParseAssignmentExpression(TypeCastState isTypeCast = NotTypeCast);
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