Rakete1111 created this revision.
This revision disallows lambdas in template parameters, as reported in PR33696.
https://reviews.llvm.org/D37442
Files:
include/clang/Basic/DiagnosticSemaKinds.td
include/clang/Sema/Sema.h
lib/Parse/ParseTemplate.cpp
lib/Sema/Sema.cpp
lib/Sema/SemaExpr.cpp
test/CXX/expr/expr.prim/expr.prim.lambda/p2-template-parameter.cpp
Index: test/CXX/expr/expr.prim/expr.prim.lambda/p2-template-parameter.cpp
===================================================================
--- test/CXX/expr/expr.prim/expr.prim.lambda/p2-template-parameter.cpp
+++ test/CXX/expr/expr.prim/expr.prim.lambda/p2-template-parameter.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -std=c++17 %s -verify
+
+template<auto> struct Nothing {};
+
+void pr33696() {
+ Nothing<[]() { return 0; }()> nothing; // expected-error{{a lambda expression cannot appear in this context}}
+}
+
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -13355,9 +13355,10 @@
void
Sema::PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
Decl *LambdaContextDecl,
- bool IsDecltype) {
+ bool IsDecltype,
+ bool IsLambdaValid) {
ExprEvalContexts.emplace_back(NewContext, ExprCleanupObjects.size(), Cleanup,
- LambdaContextDecl, IsDecltype);
+ LambdaContextDecl, IsDecltype, IsLambdaValid);
Cleanup.reset();
if (!MaybeODRUseExprs.empty())
std::swap(MaybeODRUseExprs, ExprEvalContexts.back().SavedMaybeODRUseExprs);
@@ -13366,9 +13367,11 @@
void
Sema::PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
ReuseLambdaContextDecl_t,
- bool IsDecltype) {
+ bool IsDecltype,
+ bool IsLambdaValid) {
Decl *ClosureContextDecl = ExprEvalContexts.back().ManglingContextDecl;
- PushExpressionEvaluationContext(NewContext, ClosureContextDecl, IsDecltype);
+ PushExpressionEvaluationContext(NewContext, ClosureContextDecl, IsDecltype,
+ IsLambdaValid);
}
void Sema::PopExpressionEvaluationContext() {
@@ -13376,7 +13379,8 @@
unsigned NumTypos = Rec.NumTypos;
if (!Rec.Lambdas.empty()) {
- if (Rec.isUnevaluated() || Rec.isConstantEvaluated()) {
+ if (!Rec.IsLambdaValid || Rec.isUnevaluated() ||
+ (Rec.isConstantEvaluated() && !getLangOpts().CPlusPlus1z)) {
unsigned D;
if (Rec.isUnevaluated()) {
// C++11 [expr.prim.lambda]p2:
@@ -13383,23 +13387,21 @@
// A lambda-expression shall not appear in an unevaluated operand
// (Clause 5).
D = diag::err_lambda_unevaluated_operand;
- } else {
+ } else if (Rec.isConstantEvaluated() && !getLangOpts().CPlusPlus1z) {
// C++1y [expr.const]p2:
// A conditional-expression e is a core constant expression unless the
// evaluation of e, following the rules of the abstract machine, would
// evaluate [...] a lambda-expression.
D = diag::err_lambda_in_constant_expression;
- }
+ } else if (!Rec.IsLambdaValid) {
+ // C++17 [expr.prim.lambda]p2:
+ // A lambda-expression shall not appear [...] in a template-argument.
+ D = diag::err_lambda_in_invalid_context;
+ } else
+ llvm_unreachable("Couldn't infer lambda error message.");
- // C++1z allows lambda expressions as core constant expressions.
- // FIXME: In C++1z, reinstate the restrictions on lambda expressions (CWG
- // 1607) from appearing within template-arguments and array-bounds that
- // are part of function-signatures. Be mindful that P0315 (Lambdas in
- // unevaluated contexts) might lift some of these restrictions in a
- // future version.
- if (!Rec.isConstantEvaluated() || !getLangOpts().CPlusPlus1z)
- for (const auto *L : Rec.Lambdas)
- Diag(L->getLocStart(), D);
+ for (const auto *L : Rec.Lambdas)
+ Diag(L->getLocStart(), D);
} else {
// Mark the capture expressions odr-used. This was deferred
// during lambda expression creation.
Index: lib/Sema/Sema.cpp
===================================================================
--- lib/Sema/Sema.cpp
+++ lib/Sema/Sema.cpp
@@ -159,7 +159,7 @@
ExprEvalContexts.emplace_back(
ExpressionEvaluationContext::PotentiallyEvaluated, 0, CleanupInfo{},
- nullptr, false);
+ nullptr, false, true);
FunctionScopes.push_back(new FunctionScopeInfo(Diags));
Index: lib/Parse/ParseTemplate.cpp
===================================================================
--- lib/Parse/ParseTemplate.cpp
+++ lib/Parse/ParseTemplate.cpp
@@ -1189,7 +1189,9 @@
// argument before trying to disambiguate.
EnterExpressionEvaluationContext EnterConstantEvaluated(
- Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+ Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated,
+ /*LambdaContextDecl=*/nullptr, /*IsDecltype=*/false,
+ /*ShouldEnter=*/true, /*IsLambdaValid=*/false);
if (isCXXTypeId(TypeIdAsTemplateArgument)) {
SourceLocation Loc = Tok.getLocation();
TypeResult TypeArg = ParseTypeName(/*Range=*/nullptr,
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -934,6 +934,10 @@
/// \brief Whether we are in a decltype expression.
bool IsDecltype;
+ /// \brief Whether we are in an expression where lambdas
+ /// are disallowed (such as template parameters).
+ bool IsLambdaValid;
+
/// \brief The number of active cleanup objects when we entered
/// this expression evaluation context.
unsigned NumCleanupObjects;
@@ -972,10 +976,11 @@
unsigned NumCleanupObjects,
CleanupInfo ParentCleanup,
Decl *ManglingContextDecl,
- bool IsDecltype)
+ bool IsDecltype,
+ bool IsLambdaValid)
: Context(Context), ParentCleanup(ParentCleanup),
- IsDecltype(IsDecltype), NumCleanupObjects(NumCleanupObjects),
- NumTypos(0),
+ IsDecltype(IsDecltype), IsLambdaValid(IsLambdaValid),
+ NumCleanupObjects(NumCleanupObjects), NumTypos(0),
ManglingContextDecl(ManglingContextDecl), MangleNumbering() { }
/// \brief Retrieve the mangling numbering context, used to consistently
@@ -3926,11 +3931,13 @@
void PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
Decl *LambdaContextDecl = nullptr,
- bool IsDecltype = false);
+ bool IsDecltype = false,
+ bool IsLambdaValid = true);
enum ReuseLambdaContextDecl_t { ReuseLambdaContextDecl };
void PushExpressionEvaluationContext(ExpressionEvaluationContext NewContext,
ReuseLambdaContextDecl_t,
- bool IsDecltype = false);
+ bool IsDecltype = false,
+ bool IsLambdaValid = true);
void PopExpressionEvaluationContext();
void DiscardCleanupsInEvaluationContext();
@@ -10546,20 +10553,22 @@
Sema::ExpressionEvaluationContext NewContext,
Decl *LambdaContextDecl = nullptr,
bool IsDecltype = false,
- bool ShouldEnter = true)
+ bool ShouldEnter = true,
+ bool IsLambdaValid = true)
: Actions(Actions), Entered(ShouldEnter) {
if (Entered)
Actions.PushExpressionEvaluationContext(NewContext, LambdaContextDecl,
- IsDecltype);
+ IsDecltype, IsLambdaValid);
}
EnterExpressionEvaluationContext(Sema &Actions,
Sema::ExpressionEvaluationContext NewContext,
Sema::ReuseLambdaContextDecl_t,
- bool IsDecltype = false)
+ bool IsDecltype = false,
+ bool IsLambdaValid = true)
: Actions(Actions) {
Actions.PushExpressionEvaluationContext(NewContext,
Sema::ReuseLambdaContextDecl,
- IsDecltype);
+ IsDecltype, IsLambdaValid);
}
enum InitListTag { InitList };
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -6506,6 +6506,8 @@
"lambda expression in an unevaluated operand">;
def err_lambda_in_constant_expression : Error<
"a lambda expression may not appear inside of a constant expression">;
+ def err_lambda_in_invalid_context : Error<
+ "a lambda expression cannot appear in this context">;
def err_lambda_return_init_list : Error<
"cannot deduce lambda return type from initializer list">;
def err_lambda_capture_default_arg : Error<
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