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SemaConcept.cpp
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//===-- SemaConcept.cpp - Semantic Analysis for Constraints and Concepts --===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements semantic analysis for C++ constraints and concepts.
//
//===----------------------------------------------------------------------===//
#include "clang/Sema/SemaConcept.h"
#include "TreeTransform.h"
#include "clang/AST/ASTLambda.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/ExprConcepts.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Basic/OperatorPrecedence.h"
#include "clang/Sema/EnterExpressionEvaluationContext.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Overload.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/Sema.h"
#include "clang/Sema/SemaDiagnostic.h"
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/Template.h"
#include "clang/Sema/TemplateDeduction.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/StringExtras.h"
#include <optional>
using namespace clang;
using namespace sema;
namespace {
class LogicalBinOp {
SourceLocation Loc;
OverloadedOperatorKind Op = OO_None;
const Expr *LHS = nullptr;
const Expr *RHS = nullptr;
public:
LogicalBinOp(const Expr *E) {
if (auto *BO = dyn_cast<BinaryOperator>(E)) {
Op = BinaryOperator::getOverloadedOperator(BO->getOpcode());
LHS = BO->getLHS();
RHS = BO->getRHS();
Loc = BO->getExprLoc();
} else if (auto *OO = dyn_cast<CXXOperatorCallExpr>(E)) {
// If OO is not || or && it might not have exactly 2 arguments.
if (OO->getNumArgs() == 2) {
Op = OO->getOperator();
LHS = OO->getArg(0);
RHS = OO->getArg(1);
Loc = OO->getOperatorLoc();
}
}
}
bool isAnd() const { return Op == OO_AmpAmp; }
bool isOr() const { return Op == OO_PipePipe; }
explicit operator bool() const { return isAnd() || isOr(); }
const Expr *getLHS() const { return LHS; }
const Expr *getRHS() const { return RHS; }
OverloadedOperatorKind getOp() const { return Op; }
ExprResult recreateBinOp(Sema &SemaRef, ExprResult LHS) const {
return recreateBinOp(SemaRef, LHS, const_cast<Expr *>(getRHS()));
}
ExprResult recreateBinOp(Sema &SemaRef, ExprResult LHS,
ExprResult RHS) const {
assert((isAnd() || isOr()) && "Not the right kind of op?");
assert((!LHS.isInvalid() && !RHS.isInvalid()) && "not good expressions?");
if (!LHS.isUsable() || !RHS.isUsable())
return ExprEmpty();
// We should just be able to 'normalize' these to the builtin Binary
// Operator, since that is how they are evaluated in constriant checks.
return BinaryOperator::Create(SemaRef.Context, LHS.get(), RHS.get(),
BinaryOperator::getOverloadedOpcode(Op),
SemaRef.Context.BoolTy, VK_PRValue,
OK_Ordinary, Loc, FPOptionsOverride{});
}
};
}
bool Sema::CheckConstraintExpression(const Expr *ConstraintExpression,
Token NextToken, bool *PossibleNonPrimary,
bool IsTrailingRequiresClause) {
// C++2a [temp.constr.atomic]p1
// ..E shall be a constant expression of type bool.
ConstraintExpression = ConstraintExpression->IgnoreParenImpCasts();
if (LogicalBinOp BO = ConstraintExpression) {
return CheckConstraintExpression(BO.getLHS(), NextToken,
PossibleNonPrimary) &&
CheckConstraintExpression(BO.getRHS(), NextToken,
PossibleNonPrimary);
} else if (auto *C = dyn_cast<ExprWithCleanups>(ConstraintExpression))
return CheckConstraintExpression(C->getSubExpr(), NextToken,
PossibleNonPrimary);
QualType Type = ConstraintExpression->getType();
auto CheckForNonPrimary = [&] {
if (!PossibleNonPrimary)
return;
*PossibleNonPrimary =
// We have the following case:
// template<typename> requires func(0) struct S { };
// 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.
//
// However, if we're in a lambda, this might also be:
// []<typename> requires var () {};
// Which also looks like a function call due to the lambda parentheses,
// but unlike the first case, isn't an error, so this check is skipped.
(NextToken.is(tok::l_paren) &&
(IsTrailingRequiresClause ||
(Type->isDependentType() &&
isa<UnresolvedLookupExpr>(ConstraintExpression) &&
!dyn_cast_if_present<LambdaScopeInfo>(getCurFunction())) ||
Type->isFunctionType() ||
Type->isSpecificBuiltinType(BuiltinType::Overload))) ||
// We have the following case:
// template<typename T> requires size_<T> == 0 struct S { };
// The user probably isn't aware of the parentheses required around
// the binary operator, and we're only going to parse 'func' as the
// first operand, and complain that it is of non-bool type.
getBinOpPrecedence(NextToken.getKind(),
/*GreaterThanIsOperator=*/true,
getLangOpts().CPlusPlus11) > prec::LogicalAnd;
};
// An atomic constraint!
if (ConstraintExpression->isTypeDependent()) {
CheckForNonPrimary();
return true;
}
if (!Context.hasSameUnqualifiedType(Type, Context.BoolTy)) {
Diag(ConstraintExpression->getExprLoc(),
diag::err_non_bool_atomic_constraint) << Type
<< ConstraintExpression->getSourceRange();
CheckForNonPrimary();
return false;
}
if (PossibleNonPrimary)
*PossibleNonPrimary = false;
return true;
}
namespace {
struct SatisfactionStackRAII {
Sema &SemaRef;
bool Inserted = false;
SatisfactionStackRAII(Sema &SemaRef, const NamedDecl *ND,
const llvm::FoldingSetNodeID &FSNID)
: SemaRef(SemaRef) {
if (ND) {
SemaRef.PushSatisfactionStackEntry(ND, FSNID);
Inserted = true;
}
}
~SatisfactionStackRAII() {
if (Inserted)
SemaRef.PopSatisfactionStackEntry();
}
};
} // namespace
template <typename ConstraintEvaluator>
static ExprResult
calculateConstraintSatisfaction(Sema &S, const Expr *ConstraintExpr,
ConstraintSatisfaction &Satisfaction,
const ConstraintEvaluator &Evaluator);
template <typename ConstraintEvaluator>
static ExprResult
calculateConstraintSatisfaction(Sema &S, const Expr *LHS,
OverloadedOperatorKind Op, const Expr *RHS,
ConstraintSatisfaction &Satisfaction,
const ConstraintEvaluator &Evaluator) {
size_t EffectiveDetailEndIndex = Satisfaction.Details.size();
ExprResult LHSRes =
calculateConstraintSatisfaction(S, LHS, Satisfaction, Evaluator);
if (LHSRes.isInvalid())
return ExprError();
bool IsLHSSatisfied = Satisfaction.IsSatisfied;
if (Op == clang::OO_PipePipe && IsLHSSatisfied)
// [temp.constr.op] p3
// A disjunction is a constraint taking two operands. To determine if
// a disjunction is satisfied, the satisfaction of the first operand
// is checked. If that is satisfied, the disjunction is satisfied.
// Otherwise, the disjunction is satisfied if and only if the second
// operand is satisfied.
// LHS is instantiated while RHS is not. Skip creating invalid BinaryOp.
return LHSRes;
if (Op == clang::OO_AmpAmp && !IsLHSSatisfied)
// [temp.constr.op] p2
// A conjunction is a constraint taking two operands. To determine if
// a conjunction is satisfied, the satisfaction of the first operand
// is checked. If that is not satisfied, the conjunction is not
// satisfied. Otherwise, the conjunction is satisfied if and only if
// the second operand is satisfied.
// LHS is instantiated while RHS is not. Skip creating invalid BinaryOp.
return LHSRes;
ExprResult RHSRes =
calculateConstraintSatisfaction(S, RHS, Satisfaction, Evaluator);
if (RHSRes.isInvalid())
return ExprError();
bool IsRHSSatisfied = Satisfaction.IsSatisfied;
// Current implementation adds diagnostic information about the falsity
// of each false atomic constraint expression when it evaluates them.
// When the evaluation results to `false || true`, the information
// generated during the evaluation of left-hand side is meaningless
// because the whole expression evaluates to true.
// The following code removes the irrelevant diagnostic information.
// FIXME: We should probably delay the addition of diagnostic information
// until we know the entire expression is false.
if (Op == clang::OO_PipePipe && IsRHSSatisfied) {
auto EffectiveDetailEnd = Satisfaction.Details.begin();
std::advance(EffectiveDetailEnd, EffectiveDetailEndIndex);
Satisfaction.Details.erase(EffectiveDetailEnd, Satisfaction.Details.end());
}
if (!LHSRes.isUsable() || !RHSRes.isUsable())
return ExprEmpty();
return BinaryOperator::Create(S.Context, LHSRes.get(), RHSRes.get(),
BinaryOperator::getOverloadedOpcode(Op),
S.Context.BoolTy, VK_PRValue, OK_Ordinary,
LHS->getBeginLoc(), FPOptionsOverride{});
}
template <typename ConstraintEvaluator>
static ExprResult
calculateConstraintSatisfaction(Sema &S, const CXXFoldExpr *FE,
ConstraintSatisfaction &Satisfaction,
const ConstraintEvaluator &Evaluator) {
bool Conjunction = FE->getOperator() == BinaryOperatorKind::BO_LAnd;
size_t EffectiveDetailEndIndex = Satisfaction.Details.size();
ExprResult Out;
if (FE->isLeftFold() && FE->getInit()) {
Out = calculateConstraintSatisfaction(S, FE->getInit(), Satisfaction,
Evaluator);
if (Out.isInvalid())
return ExprError();
// If the first clause of a conjunction is not satisfied,
// or if the first clause of a disjection is satisfied,
// we have established satisfaction of the whole constraint
// and we should not continue further.
if (Conjunction != Satisfaction.IsSatisfied)
return Out;
}
std::optional<unsigned> NumExpansions =
Evaluator.EvaluateFoldExpandedConstraintSize(FE);
if (!NumExpansions)
return ExprError();
for (unsigned I = 0; I < *NumExpansions; I++) {
Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(S, I);
ExprResult Res = calculateConstraintSatisfaction(S, FE->getPattern(),
Satisfaction, Evaluator);
if (Res.isInvalid())
return ExprError();
bool IsRHSSatisfied = Satisfaction.IsSatisfied;
if (!Conjunction && IsRHSSatisfied) {
auto EffectiveDetailEnd = Satisfaction.Details.begin();
std::advance(EffectiveDetailEnd, EffectiveDetailEndIndex);
Satisfaction.Details.erase(EffectiveDetailEnd,
Satisfaction.Details.end());
}
if (Out.isUnset())
Out = Res;
else if (!Res.isUnset()) {
Out = BinaryOperator::Create(
S.Context, Out.get(), Res.get(), FE->getOperator(), S.Context.BoolTy,
VK_PRValue, OK_Ordinary, FE->getBeginLoc(), FPOptionsOverride{});
}
if (Conjunction != IsRHSSatisfied)
return Out;
}
if (FE->isRightFold() && FE->getInit()) {
ExprResult Res = calculateConstraintSatisfaction(S, FE->getInit(),
Satisfaction, Evaluator);
if (Out.isInvalid())
return ExprError();
if (Out.isUnset())
Out = Res;
else if (!Res.isUnset()) {
Out = BinaryOperator::Create(
S.Context, Out.get(), Res.get(), FE->getOperator(), S.Context.BoolTy,
VK_PRValue, OK_Ordinary, FE->getBeginLoc(), FPOptionsOverride{});
}
}
if (Out.isUnset()) {
Satisfaction.IsSatisfied = Conjunction;
Out = S.BuildEmptyCXXFoldExpr(FE->getBeginLoc(), FE->getOperator());
}
return Out;
}
template <typename ConstraintEvaluator>
static ExprResult
calculateConstraintSatisfaction(Sema &S, const Expr *ConstraintExpr,
ConstraintSatisfaction &Satisfaction,
const ConstraintEvaluator &Evaluator) {
ConstraintExpr = ConstraintExpr->IgnoreParenImpCasts();
if (LogicalBinOp BO = ConstraintExpr)
return calculateConstraintSatisfaction(
S, BO.getLHS(), BO.getOp(), BO.getRHS(), Satisfaction, Evaluator);
if (auto *C = dyn_cast<ExprWithCleanups>(ConstraintExpr)) {
// These aren't evaluated, so we don't care about cleanups, so we can just
// evaluate these as if the cleanups didn't exist.
return calculateConstraintSatisfaction(S, C->getSubExpr(), Satisfaction,
Evaluator);
}
if (auto *FE = dyn_cast<CXXFoldExpr>(ConstraintExpr);
FE && S.getLangOpts().CPlusPlus26 &&
(FE->getOperator() == BinaryOperatorKind::BO_LAnd ||
FE->getOperator() == BinaryOperatorKind::BO_LOr)) {
return calculateConstraintSatisfaction(S, FE, Satisfaction, Evaluator);
}
// An atomic constraint expression
ExprResult SubstitutedAtomicExpr =
Evaluator.EvaluateAtomicConstraint(ConstraintExpr);
if (SubstitutedAtomicExpr.isInvalid())
return ExprError();
if (!SubstitutedAtomicExpr.isUsable())
// Evaluator has decided satisfaction without yielding an expression.
return ExprEmpty();
// We don't have the ability to evaluate this, since it contains a
// RecoveryExpr, so we want to fail overload resolution. Otherwise,
// we'd potentially pick up a different overload, and cause confusing
// diagnostics. SO, add a failure detail that will cause us to make this
// overload set not viable.
if (SubstitutedAtomicExpr.get()->containsErrors()) {
Satisfaction.IsSatisfied = false;
Satisfaction.ContainsErrors = true;
PartialDiagnostic Msg = S.PDiag(diag::note_constraint_references_error);
SmallString<128> DiagString;
DiagString = ": ";
Msg.EmitToString(S.getDiagnostics(), DiagString);
unsigned MessageSize = DiagString.size();
char *Mem = new (S.Context) char[MessageSize];
memcpy(Mem, DiagString.c_str(), MessageSize);
Satisfaction.Details.emplace_back(
new (S.Context) ConstraintSatisfaction::SubstitutionDiagnostic{
SubstitutedAtomicExpr.get()->getBeginLoc(),
StringRef(Mem, MessageSize)});
return SubstitutedAtomicExpr;
}
EnterExpressionEvaluationContext ConstantEvaluated(
S, Sema::ExpressionEvaluationContext::ConstantEvaluated);
SmallVector<PartialDiagnosticAt, 2> EvaluationDiags;
Expr::EvalResult EvalResult;
EvalResult.Diag = &EvaluationDiags;
if (!SubstitutedAtomicExpr.get()->EvaluateAsConstantExpr(EvalResult,
S.Context) ||
!EvaluationDiags.empty()) {
// C++2a [temp.constr.atomic]p1
// ...E shall be a constant expression of type bool.
S.Diag(SubstitutedAtomicExpr.get()->getBeginLoc(),
diag::err_non_constant_constraint_expression)
<< SubstitutedAtomicExpr.get()->getSourceRange();
for (const PartialDiagnosticAt &PDiag : EvaluationDiags)
S.Diag(PDiag.first, PDiag.second);
return ExprError();
}
assert(EvalResult.Val.isInt() &&
"evaluating bool expression didn't produce int");
Satisfaction.IsSatisfied = EvalResult.Val.getInt().getBoolValue();
if (!Satisfaction.IsSatisfied)
Satisfaction.Details.emplace_back(SubstitutedAtomicExpr.get());
return SubstitutedAtomicExpr;
}
static bool
DiagRecursiveConstraintEval(Sema &S, llvm::FoldingSetNodeID &ID,
const NamedDecl *Templ, const Expr *E,
const MultiLevelTemplateArgumentList &MLTAL) {
E->Profile(ID, S.Context, /*Canonical=*/true);
for (const auto &List : MLTAL)
for (const auto &TemplateArg : List.Args)
TemplateArg.Profile(ID, S.Context);
// Note that we have to do this with our own collection, because there are
// times where a constraint-expression check can cause us to need to evaluate
// other constriants that are unrelated, such as when evaluating a recovery
// expression, or when trying to determine the constexpr-ness of special
// members. Otherwise we could just use the
// Sema::InstantiatingTemplate::isAlreadyBeingInstantiated function.
if (S.SatisfactionStackContains(Templ, ID)) {
S.Diag(E->getExprLoc(), diag::err_constraint_depends_on_self)
<< const_cast<Expr *>(E) << E->getSourceRange();
return true;
}
return false;
}
static ExprResult calculateConstraintSatisfaction(
Sema &S, const NamedDecl *Template, SourceLocation TemplateNameLoc,
const MultiLevelTemplateArgumentList &MLTAL, const Expr *ConstraintExpr,
ConstraintSatisfaction &Satisfaction) {
struct ConstraintEvaluator {
Sema &S;
const NamedDecl *Template;
SourceLocation TemplateNameLoc;
const MultiLevelTemplateArgumentList &MLTAL;
ConstraintSatisfaction &Satisfaction;
ExprResult EvaluateAtomicConstraint(const Expr *AtomicExpr) const {
EnterExpressionEvaluationContext ConstantEvaluated(
S, Sema::ExpressionEvaluationContext::ConstantEvaluated,
Sema::ReuseLambdaContextDecl);
// Atomic constraint - substitute arguments and check satisfaction.
ExprResult SubstitutedExpression;
{
TemplateDeductionInfo Info(TemplateNameLoc);
Sema::InstantiatingTemplate Inst(
S, AtomicExpr->getBeginLoc(),
Sema::InstantiatingTemplate::ConstraintSubstitution{},
const_cast<NamedDecl *>(Template), Info,
AtomicExpr->getSourceRange());
if (Inst.isInvalid())
return ExprError();
llvm::FoldingSetNodeID ID;
if (Template &&
DiagRecursiveConstraintEval(S, ID, Template, AtomicExpr, MLTAL)) {
Satisfaction.IsSatisfied = false;
Satisfaction.ContainsErrors = true;
return ExprEmpty();
}
SatisfactionStackRAII StackRAII(S, Template, ID);
// We do not want error diagnostics escaping here.
Sema::SFINAETrap Trap(S);
SubstitutedExpression =
S.SubstConstraintExpr(const_cast<Expr *>(AtomicExpr), MLTAL);
if (SubstitutedExpression.isInvalid() || Trap.hasErrorOccurred()) {
// C++2a [temp.constr.atomic]p1
// ...If substitution results in an invalid type or expression, the
// constraint is not satisfied.
if (!Trap.hasErrorOccurred())
// A non-SFINAE error has occurred as a result of this
// substitution.
return ExprError();
PartialDiagnosticAt SubstDiag{SourceLocation(),
PartialDiagnostic::NullDiagnostic()};
Info.takeSFINAEDiagnostic(SubstDiag);
// FIXME: Concepts: This is an unfortunate consequence of there
// being no serialization code for PartialDiagnostics and the fact
// that serializing them would likely take a lot more storage than
// just storing them as strings. We would still like, in the
// future, to serialize the proper PartialDiagnostic as serializing
// it as a string defeats the purpose of the diagnostic mechanism.
SmallString<128> DiagString;
DiagString = ": ";
SubstDiag.second.EmitToString(S.getDiagnostics(), DiagString);
unsigned MessageSize = DiagString.size();
char *Mem = new (S.Context) char[MessageSize];
memcpy(Mem, DiagString.c_str(), MessageSize);
Satisfaction.Details.emplace_back(
new (S.Context) ConstraintSatisfaction::SubstitutionDiagnostic{
SubstDiag.first, StringRef(Mem, MessageSize)});
Satisfaction.IsSatisfied = false;
return ExprEmpty();
}
}
if (!S.CheckConstraintExpression(SubstitutedExpression.get()))
return ExprError();
// [temp.constr.atomic]p3: To determine if an atomic constraint is
// satisfied, the parameter mapping and template arguments are first
// substituted into its expression. If substitution results in an
// invalid type or expression, the constraint is not satisfied.
// Otherwise, the lvalue-to-rvalue conversion is performed if necessary,
// and E shall be a constant expression of type bool.
//
// Perform the L to R Value conversion if necessary. We do so for all
// non-PRValue categories, else we fail to extend the lifetime of
// temporaries, and that fails the constant expression check.
if (!SubstitutedExpression.get()->isPRValue())
SubstitutedExpression = ImplicitCastExpr::Create(
S.Context, SubstitutedExpression.get()->getType(),
CK_LValueToRValue, SubstitutedExpression.get(),
/*BasePath=*/nullptr, VK_PRValue, FPOptionsOverride());
return SubstitutedExpression;
}
std::optional<unsigned>
EvaluateFoldExpandedConstraintSize(const CXXFoldExpr *FE) const {
// We should ignore errors in the presence of packs of different size.
Sema::SFINAETrap Trap(S);
Expr *Pattern = FE->getPattern();
SmallVector<UnexpandedParameterPack, 2> Unexpanded;
S.collectUnexpandedParameterPacks(Pattern, Unexpanded);
assert(!Unexpanded.empty() && "Pack expansion without parameter packs?");
bool Expand = true;
bool RetainExpansion = false;
std::optional<unsigned> OrigNumExpansions = FE->getNumExpansions(),
NumExpansions = OrigNumExpansions;
if (S.CheckParameterPacksForExpansion(
FE->getEllipsisLoc(), Pattern->getSourceRange(), Unexpanded,
MLTAL, Expand, RetainExpansion, NumExpansions) ||
!Expand || RetainExpansion)
return std::nullopt;
if (NumExpansions && S.getLangOpts().BracketDepth < NumExpansions) {
S.Diag(FE->getEllipsisLoc(),
clang::diag::err_fold_expression_limit_exceeded)
<< *NumExpansions << S.getLangOpts().BracketDepth
<< FE->getSourceRange();
S.Diag(FE->getEllipsisLoc(), diag::note_bracket_depth);
return std::nullopt;
}
return NumExpansions;
}
};
return calculateConstraintSatisfaction(
S, ConstraintExpr, Satisfaction,
ConstraintEvaluator{S, Template, TemplateNameLoc, MLTAL, Satisfaction});
}
static bool CheckConstraintSatisfaction(
Sema &S, const NamedDecl *Template, ArrayRef<const Expr *> ConstraintExprs,
llvm::SmallVectorImpl<Expr *> &Converted,
const MultiLevelTemplateArgumentList &TemplateArgsLists,
SourceRange TemplateIDRange, ConstraintSatisfaction &Satisfaction) {
if (ConstraintExprs.empty()) {
Satisfaction.IsSatisfied = true;
return false;
}
if (TemplateArgsLists.isAnyArgInstantiationDependent()) {
// No need to check satisfaction for dependent constraint expressions.
Satisfaction.IsSatisfied = true;
return false;
}
ArrayRef<TemplateArgument> TemplateArgs =
TemplateArgsLists.getNumSubstitutedLevels() > 0
? TemplateArgsLists.getOutermost()
: ArrayRef<TemplateArgument> {};
Sema::InstantiatingTemplate Inst(S, TemplateIDRange.getBegin(),
Sema::InstantiatingTemplate::ConstraintsCheck{},
const_cast<NamedDecl *>(Template), TemplateArgs, TemplateIDRange);
if (Inst.isInvalid())
return true;
for (const Expr *ConstraintExpr : ConstraintExprs) {
ExprResult Res = calculateConstraintSatisfaction(
S, Template, TemplateIDRange.getBegin(), TemplateArgsLists,
ConstraintExpr, Satisfaction);
if (Res.isInvalid())
return true;
Converted.push_back(Res.get());
if (!Satisfaction.IsSatisfied) {
// Backfill the 'converted' list with nulls so we can keep the Converted
// and unconverted lists in sync.
Converted.append(ConstraintExprs.size() - Converted.size(), nullptr);
// [temp.constr.op] p2
// [...] To determine if a conjunction is satisfied, the satisfaction
// of the first operand is checked. If that is not satisfied, the
// conjunction is not satisfied. [...]
return false;
}
}
return false;
}
bool Sema::CheckConstraintSatisfaction(
const NamedDecl *Template, ArrayRef<const Expr *> ConstraintExprs,
llvm::SmallVectorImpl<Expr *> &ConvertedConstraints,
const MultiLevelTemplateArgumentList &TemplateArgsLists,
SourceRange TemplateIDRange, ConstraintSatisfaction &OutSatisfaction) {
if (ConstraintExprs.empty()) {
OutSatisfaction.IsSatisfied = true;
return false;
}
if (!Template) {
return ::CheckConstraintSatisfaction(
*this, nullptr, ConstraintExprs, ConvertedConstraints,
TemplateArgsLists, TemplateIDRange, OutSatisfaction);
}
// Invalid templates could make their way here. Substituting them could result
// in dependent expressions.
if (Template->isInvalidDecl()) {
OutSatisfaction.IsSatisfied = false;
return true;
}
// A list of the template argument list flattened in a predictible manner for
// the purposes of caching. The ConstraintSatisfaction type is in AST so it
// has no access to the MultiLevelTemplateArgumentList, so this has to happen
// here.
llvm::SmallVector<TemplateArgument, 4> FlattenedArgs;
for (auto List : TemplateArgsLists)
FlattenedArgs.insert(FlattenedArgs.end(), List.Args.begin(),
List.Args.end());
llvm::FoldingSetNodeID ID;
ConstraintSatisfaction::Profile(ID, Context, Template, FlattenedArgs);
void *InsertPos;
if (auto *Cached = SatisfactionCache.FindNodeOrInsertPos(ID, InsertPos)) {
OutSatisfaction = *Cached;
return false;
}
auto Satisfaction =
std::make_unique<ConstraintSatisfaction>(Template, FlattenedArgs);
if (::CheckConstraintSatisfaction(*this, Template, ConstraintExprs,
ConvertedConstraints, TemplateArgsLists,
TemplateIDRange, *Satisfaction)) {
OutSatisfaction = *Satisfaction;
return true;
}
if (auto *Cached = SatisfactionCache.FindNodeOrInsertPos(ID, InsertPos)) {
// The evaluation of this constraint resulted in us trying to re-evaluate it
// recursively. This isn't really possible, except we try to form a
// RecoveryExpr as a part of the evaluation. If this is the case, just
// return the 'cached' version (which will have the same result), and save
// ourselves the extra-insert. If it ever becomes possible to legitimately
// recursively check a constraint, we should skip checking the 'inner' one
// above, and replace the cached version with this one, as it would be more
// specific.
OutSatisfaction = *Cached;
return false;
}
// Else we can simply add this satisfaction to the list.
OutSatisfaction = *Satisfaction;
// We cannot use InsertPos here because CheckConstraintSatisfaction might have
// invalidated it.
// Note that entries of SatisfactionCache are deleted in Sema's destructor.
SatisfactionCache.InsertNode(Satisfaction.release());
return false;
}
bool Sema::CheckConstraintSatisfaction(const Expr *ConstraintExpr,
ConstraintSatisfaction &Satisfaction) {
struct ConstraintEvaluator {
Sema &S;
ExprResult EvaluateAtomicConstraint(const Expr *AtomicExpr) const {
return S.PerformContextuallyConvertToBool(const_cast<Expr *>(AtomicExpr));
}
std::optional<unsigned>
EvaluateFoldExpandedConstraintSize(const CXXFoldExpr *FE) const {
return 0;
}
};
return calculateConstraintSatisfaction(*this, ConstraintExpr, Satisfaction,
ConstraintEvaluator{*this})
.isInvalid();
}
bool Sema::addInstantiatedCapturesToScope(
FunctionDecl *Function, const FunctionDecl *PatternDecl,
LocalInstantiationScope &Scope,
const MultiLevelTemplateArgumentList &TemplateArgs) {
const auto *LambdaClass = cast<CXXMethodDecl>(Function)->getParent();
const auto *LambdaPattern = cast<CXXMethodDecl>(PatternDecl)->getParent();
unsigned Instantiated = 0;
auto AddSingleCapture = [&](const ValueDecl *CapturedPattern,
unsigned Index) {
ValueDecl *CapturedVar = LambdaClass->getCapture(Index)->getCapturedVar();
if (CapturedVar->isInitCapture())
Scope.InstantiatedLocal(CapturedPattern, CapturedVar);
};
for (const LambdaCapture &CapturePattern : LambdaPattern->captures()) {
if (!CapturePattern.capturesVariable()) {
Instantiated++;
continue;
}
const ValueDecl *CapturedPattern = CapturePattern.getCapturedVar();
if (!CapturedPattern->isParameterPack()) {
AddSingleCapture(CapturedPattern, Instantiated++);
} else {
Scope.MakeInstantiatedLocalArgPack(CapturedPattern);
std::optional<unsigned> NumArgumentsInExpansion =
getNumArgumentsInExpansion(CapturedPattern->getType(), TemplateArgs);
if (!NumArgumentsInExpansion)
continue;
for (unsigned Arg = 0; Arg < *NumArgumentsInExpansion; ++Arg)
AddSingleCapture(CapturedPattern, Instantiated++);
}
}
return false;
}
bool Sema::SetupConstraintScope(
FunctionDecl *FD, std::optional<ArrayRef<TemplateArgument>> TemplateArgs,
const MultiLevelTemplateArgumentList &MLTAL,
LocalInstantiationScope &Scope) {
if (FD->isTemplateInstantiation() && FD->getPrimaryTemplate()) {
FunctionTemplateDecl *PrimaryTemplate = FD->getPrimaryTemplate();
InstantiatingTemplate Inst(
*this, FD->getPointOfInstantiation(),
Sema::InstantiatingTemplate::ConstraintsCheck{}, PrimaryTemplate,
TemplateArgs ? *TemplateArgs : ArrayRef<TemplateArgument>{},
SourceRange());
if (Inst.isInvalid())
return true;
// addInstantiatedParametersToScope creates a map of 'uninstantiated' to
// 'instantiated' parameters and adds it to the context. For the case where
// this function is a template being instantiated NOW, we also need to add
// the list of current template arguments to the list so that they also can
// be picked out of the map.
if (auto *SpecArgs = FD->getTemplateSpecializationArgs()) {
MultiLevelTemplateArgumentList JustTemplArgs(FD, SpecArgs->asArray(),
/*Final=*/false);
if (addInstantiatedParametersToScope(
FD, PrimaryTemplate->getTemplatedDecl(), Scope, JustTemplArgs))
return true;
}
// If this is a member function, make sure we get the parameters that
// reference the original primary template.
// We walk up the instantiated template chain so that nested lambdas get
// handled properly.
// We should only collect instantiated parameters from the primary template.
// Otherwise, we may have mismatched template parameter depth!
if (FunctionTemplateDecl *FromMemTempl =
PrimaryTemplate->getInstantiatedFromMemberTemplate()) {
while (FromMemTempl->getInstantiatedFromMemberTemplate())
FromMemTempl = FromMemTempl->getInstantiatedFromMemberTemplate();
if (addInstantiatedParametersToScope(FD, FromMemTempl->getTemplatedDecl(),
Scope, MLTAL))
return true;
}
return false;
}
if (FD->getTemplatedKind() == FunctionDecl::TK_MemberSpecialization ||
FD->getTemplatedKind() == FunctionDecl::TK_DependentNonTemplate) {
FunctionDecl *InstantiatedFrom =
FD->getTemplatedKind() == FunctionDecl::TK_MemberSpecialization
? FD->getInstantiatedFromMemberFunction()
: FD->getInstantiatedFromDecl();
InstantiatingTemplate Inst(
*this, FD->getPointOfInstantiation(),
Sema::InstantiatingTemplate::ConstraintsCheck{}, InstantiatedFrom,
TemplateArgs ? *TemplateArgs : ArrayRef<TemplateArgument>{},
SourceRange());
if (Inst.isInvalid())
return true;
// Case where this was not a template, but instantiated as a
// child-function.
if (addInstantiatedParametersToScope(FD, InstantiatedFrom, Scope, MLTAL))
return true;
}
return false;
}
// This function collects all of the template arguments for the purposes of
// constraint-instantiation and checking.
std::optional<MultiLevelTemplateArgumentList>
Sema::SetupConstraintCheckingTemplateArgumentsAndScope(
FunctionDecl *FD, std::optional<ArrayRef<TemplateArgument>> TemplateArgs,
LocalInstantiationScope &Scope) {
MultiLevelTemplateArgumentList MLTAL;
// Collect the list of template arguments relative to the 'primary' template.
// We need the entire list, since the constraint is completely uninstantiated
// at this point.
MLTAL =
getTemplateInstantiationArgs(FD, FD->getLexicalDeclContext(),
/*Final=*/false, /*Innermost=*/std::nullopt,
/*RelativeToPrimary=*/true,
/*Pattern=*/nullptr,
/*ForConstraintInstantiation=*/true);
if (SetupConstraintScope(FD, TemplateArgs, MLTAL, Scope))
return std::nullopt;
return MLTAL;
}
bool Sema::CheckFunctionConstraints(const FunctionDecl *FD,
ConstraintSatisfaction &Satisfaction,
SourceLocation UsageLoc,
bool ForOverloadResolution) {
// Don't check constraints if the function is dependent. Also don't check if
// this is a function template specialization, as the call to
// CheckinstantiatedFunctionTemplateConstraints after this will check it
// better.
if (FD->isDependentContext() ||
FD->getTemplatedKind() ==
FunctionDecl::TK_FunctionTemplateSpecialization) {
Satisfaction.IsSatisfied = true;
return false;
}
// A lambda conversion operator has the same constraints as the call operator
// and constraints checking relies on whether we are in a lambda call operator
// (and may refer to its parameters), so check the call operator instead.
// Note that the declarations outside of the lambda should also be
// considered. Turning on the 'ForOverloadResolution' flag results in the
// LocalInstantiationScope not looking into its parents, but we can still
// access Decls from the parents while building a lambda RAII scope later.
if (const auto *MD = dyn_cast<CXXConversionDecl>(FD);
MD && isLambdaConversionOperator(const_cast<CXXConversionDecl *>(MD)))
return CheckFunctionConstraints(MD->getParent()->getLambdaCallOperator(),
Satisfaction, UsageLoc,
/*ShouldAddDeclsFromParentScope=*/true);
DeclContext *CtxToSave = const_cast<FunctionDecl *>(FD);
while (isLambdaCallOperator(CtxToSave) || FD->isTransparentContext()) {
if (isLambdaCallOperator(CtxToSave))
CtxToSave = CtxToSave->getParent()->getParent();
else
CtxToSave = CtxToSave->getNonTransparentContext();
}
ContextRAII SavedContext{*this, CtxToSave};
LocalInstantiationScope Scope(*this, !ForOverloadResolution);
std::optional<MultiLevelTemplateArgumentList> MLTAL =
SetupConstraintCheckingTemplateArgumentsAndScope(
const_cast<FunctionDecl *>(FD), {}, Scope);
if (!MLTAL)
return true;
Qualifiers ThisQuals;
CXXRecordDecl *Record = nullptr;
if (auto *Method = dyn_cast<CXXMethodDecl>(FD)) {
ThisQuals = Method->getMethodQualifiers();
Record = const_cast<CXXRecordDecl *>(Method->getParent());
}
CXXThisScopeRAII ThisScope(*this, Record, ThisQuals, Record != nullptr);
LambdaScopeForCallOperatorInstantiationRAII LambdaScope(
*this, const_cast<FunctionDecl *>(FD), *MLTAL, Scope,
ForOverloadResolution);
return CheckConstraintSatisfaction(
FD, {FD->getTrailingRequiresClause()}, *MLTAL,
SourceRange(UsageLoc.isValid() ? UsageLoc : FD->getLocation()),
Satisfaction);
}
// Figure out the to-translation-unit depth for this function declaration for
// the purpose of seeing if they differ by constraints. This isn't the same as
// getTemplateDepth, because it includes already instantiated parents.
static unsigned
CalculateTemplateDepthForConstraints(Sema &S, const NamedDecl *ND,
bool SkipForSpecialization = false) {
MultiLevelTemplateArgumentList MLTAL = S.getTemplateInstantiationArgs(
ND, ND->getLexicalDeclContext(), /*Final=*/false,
/*Innermost=*/std::nullopt,
/*RelativeToPrimary=*/true,
/*Pattern=*/nullptr,
/*ForConstraintInstantiation=*/true, SkipForSpecialization);
return MLTAL.getNumLevels();
}
namespace {
class AdjustConstraintDepth : public TreeTransform<AdjustConstraintDepth> {
unsigned TemplateDepth = 0;
public:
using inherited = TreeTransform<AdjustConstraintDepth>;
AdjustConstraintDepth(Sema &SemaRef, unsigned TemplateDepth)
: inherited(SemaRef), TemplateDepth(TemplateDepth) {}
using inherited::TransformTemplateTypeParmType;
QualType TransformTemplateTypeParmType(TypeLocBuilder &TLB,
TemplateTypeParmTypeLoc TL, bool) {
const TemplateTypeParmType *T = TL.getTypePtr();
TemplateTypeParmDecl *NewTTPDecl = nullptr;
if (TemplateTypeParmDecl *OldTTPDecl = T->getDecl())
NewTTPDecl = cast_or_null<TemplateTypeParmDecl>(
TransformDecl(TL.getNameLoc(), OldTTPDecl));
QualType Result = getSema().Context.getTemplateTypeParmType(
T->getDepth() + TemplateDepth, T->getIndex(), T->isParameterPack(),
NewTTPDecl);
TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
NewTL.setNameLoc(TL.getNameLoc());
return Result;
}
};
} // namespace
static const Expr *SubstituteConstraintExpressionWithoutSatisfaction(
Sema &S, const Sema::TemplateCompareNewDeclInfo &DeclInfo,
const Expr *ConstrExpr) {
MultiLevelTemplateArgumentList MLTAL = S.getTemplateInstantiationArgs(
DeclInfo.getDecl(), DeclInfo.getLexicalDeclContext(), /*Final=*/false,
/*Innermost=*/std::nullopt,
/*RelativeToPrimary=*/true,
/*Pattern=*/nullptr, /*ForConstraintInstantiation=*/true,
/*SkipForSpecialization*/ false);
if (MLTAL.getNumSubstitutedLevels() == 0)
return ConstrExpr;
Sema::SFINAETrap SFINAE(S, /*AccessCheckingSFINAE=*/false);
Sema::InstantiatingTemplate Inst(
S, DeclInfo.getLocation(),
Sema::InstantiatingTemplate::ConstraintNormalization{},
const_cast<NamedDecl *>(DeclInfo.getDecl()), SourceRange{});
if (Inst.isInvalid())
return nullptr;
// Set up a dummy 'instantiation' scope in the case of reference to function
// parameters that the surrounding function hasn't been instantiated yet. Note
// this may happen while we're comparing two templates' constraint
// equivalence.
LocalInstantiationScope ScopeForParameters(S, /*CombineWithOuterScope=*/true);
if (auto *FD = DeclInfo.getDecl()->getAsFunction())
for (auto *PVD : FD->parameters()) {
if (!PVD->isParameterPack()) {
ScopeForParameters.InstantiatedLocal(PVD, PVD);
continue;
}
// This is hacky: we're mapping the parameter pack to a size-of-1 argument
// to avoid building SubstTemplateTypeParmPackTypes for
// PackExpansionTypes. The SubstTemplateTypeParmPackType node would
// otherwise reference the AssociatedDecl of the template arguments, which
// is, in this case, the template declaration.
//
// However, as we are in the process of comparing potential
// re-declarations, the canonical declaration is the declaration itself at
// this point. So if we didn't expand these packs, we would end up with an
// incorrect profile difference because we will be profiling the
// canonical types!
//
// FIXME: Improve the "no-transform" machinery in FindInstantiatedDecl so
// that we can eliminate the Scope in the cases where the declarations are
// not necessarily instantiated. It would also benefit the noexcept
// specifier comparison.
ScopeForParameters.MakeInstantiatedLocalArgPack(PVD);
ScopeForParameters.InstantiatedLocalPackArg(PVD, PVD);
}
std::optional<Sema::CXXThisScopeRAII> ThisScope;
// See TreeTransform::RebuildTemplateSpecializationType. A context scope is
// essential for having an injected class as the canonical type for a template