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TypeCheckConstraints.cpp
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//===--- TypeCheckConstraints.cpp - Constraint-based Type Checking --------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file provides high-level entry points that use constraint
// systems for type checking, as well as a few miscellaneous helper
// functions that support the constraint system.
//
//===----------------------------------------------------------------------===//
#include "MiscDiagnostics.h"
#include "TypeCheckAvailability.h"
#include "TypeChecker.h"
#include "swift/AST/ASTVisitor.h"
#include "swift/AST/ASTWalker.h"
#include "swift/AST/DiagnosticSuppression.h"
#include "swift/AST/ExistentialLayout.h"
#include "swift/AST/Initializer.h"
#include "swift/AST/PrettyStackTrace.h"
#include "swift/AST/SubstitutionMap.h"
#include "swift/AST/TypeCheckRequests.h"
#include "swift/Basic/Statistic.h"
#include "swift/IDE/TypeCheckCompletionCallback.h"
#include "swift/Sema/ConstraintSystem.h"
#include "swift/Sema/SolutionResult.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/SaveAndRestore.h"
#include "llvm/Support/raw_ostream.h"
#include <iterator>
#include <map>
#include <memory>
#include <tuple>
#include <utility>
using namespace swift;
using namespace constraints;
//===----------------------------------------------------------------------===//
// Type variable implementation.
//===----------------------------------------------------------------------===//
#pragma mark Type variable implementation
void TypeVariableType::Implementation::print(llvm::raw_ostream &OS) {
PrintOptions PO;
PO.PrintTypesForDebugging = true;
getTypeVariable()->print(OS, PO);
SmallVector<TypeVariableOptions, 4> bindingOptions;
if (canBindToLValue())
bindingOptions.push_back(TypeVariableOptions::TVO_CanBindToLValue);
if (canBindToInOut())
bindingOptions.push_back(TypeVariableOptions::TVO_CanBindToInOut);
if (canBindToNoEscape())
bindingOptions.push_back(TypeVariableOptions::TVO_CanBindToNoEscape);
if (canBindToHole())
bindingOptions.push_back(TypeVariableOptions::TVO_CanBindToHole);
if (canBindToPack())
bindingOptions.push_back(TypeVariableOptions::TVO_CanBindToPack);
if (isPackExpansion())
bindingOptions.push_back(TypeVariableOptions::TVO_PackExpansion);
if (!bindingOptions.empty()) {
OS << " [allows bindings to: ";
interleave(bindingOptions, OS,
[&](TypeVariableOptions option) {
(OS << getTypeVariableOptions(option));},
", ");
OS << "]";
}
}
SavedTypeVariableBinding::SavedTypeVariableBinding(TypeVariableType *typeVar)
: TypeVar(typeVar), Options(typeVar->getImpl().getRawOptions()),
ParentOrFixed(typeVar->getImpl().ParentOrFixed) { }
void SavedTypeVariableBinding::restore() {
TypeVar->getImpl().setRawOptions(Options);
TypeVar->getImpl().ParentOrFixed = ParentOrFixed;
}
GenericTypeParamType *
TypeVariableType::Implementation::getGenericParameter() const {
return locator ? locator->getGenericParameter() : nullptr;
}
std::optional<ExprKind>
TypeVariableType::Implementation::getAtomicLiteralKind() const {
if (!locator || !locator->directlyAt<LiteralExpr>())
return std::nullopt;
auto kind = getAsExpr(locator->getAnchor())->getKind();
switch (kind) {
case ExprKind::IntegerLiteral:
case ExprKind::FloatLiteral:
case ExprKind::StringLiteral:
case ExprKind::BooleanLiteral:
case ExprKind::NilLiteral:
return kind;
default:
return std::nullopt;
}
}
bool TypeVariableType::Implementation::isClosureType() const {
if (!(locator && locator->getAnchor()))
return false;
return isExpr<ClosureExpr>(locator->getAnchor()) && locator->getPath().empty();
}
bool TypeVariableType::Implementation::isTapType() const {
return locator && locator->directlyAt<TapExpr>();
}
bool TypeVariableType::Implementation::isClosureParameterType() const {
if (!(locator && locator->getAnchor()))
return false;
return isExpr<ClosureExpr>(locator->getAnchor()) &&
locator->isLastElement<LocatorPathElt::TupleElement>();
}
bool TypeVariableType::Implementation::isClosureResultType() const {
if (!(locator && locator->getAnchor()))
return false;
return isExpr<ClosureExpr>(locator->getAnchor()) &&
locator->isLastElement<LocatorPathElt::ClosureResult>();
}
bool TypeVariableType::Implementation::isKeyPathType() const {
return locator && locator->isKeyPathType();
}
bool TypeVariableType::Implementation::isKeyPathRoot() const {
return locator && locator->isKeyPathRoot();
}
bool TypeVariableType::Implementation::isKeyPathValue() const {
return locator && locator->isKeyPathValue();
}
bool TypeVariableType::Implementation::isKeyPathSubscriptIndex() const {
return locator &&
locator->isLastElement<LocatorPathElt::KeyPathSubscriptIndex>();
}
bool TypeVariableType::Implementation::isSubscriptResultType() const {
if (!(locator && locator->getAnchor()))
return false;
if (!locator->isLastElement<LocatorPathElt::FunctionResult>())
return false;
if (isExpr<SubscriptExpr>(locator->getAnchor()))
return true;
auto *KP = getAsExpr<KeyPathExpr>(locator->getAnchor());
if (!KP)
return false;
auto componentLoc = locator->findFirst<LocatorPathElt::KeyPathComponent>();
if (!componentLoc)
return false;
auto &component = KP->getComponents()[componentLoc->getIndex()];
return component.getKind() == KeyPathExpr::Component::Kind::Subscript ||
component.getKind() ==
KeyPathExpr::Component::Kind::UnresolvedSubscript;
}
bool TypeVariableType::Implementation::isParameterPack() const {
return locator
&& locator->isForGenericParameter()
&& locator->getGenericParameter()->isParameterPack();
}
bool TypeVariableType::Implementation::isCodeCompletionToken() const {
return locator && locator->directlyAt<CodeCompletionExpr>();
}
bool TypeVariableType::Implementation::isOpaqueType() const {
if (!locator)
return false;
auto GP = locator->getLastElementAs<LocatorPathElt::GenericParameter>();
if (!GP)
return false;
if (auto *GPT = GP->getType()->getAs<GenericTypeParamType>()) {
auto *decl = GPT->getDecl();
return decl && decl->isOpaqueType();
}
return false;
}
bool TypeVariableType::Implementation::isCollectionLiteralType() const {
return locator && (locator->directlyAt<ArrayExpr>() ||
locator->directlyAt<DictionaryExpr>());
}
void *operator new(size_t bytes, ConstraintSystem& cs,
size_t alignment) {
return cs.getAllocator().Allocate(bytes, alignment);
}
bool constraints::computeTupleShuffle(TupleType *fromTuple,
TupleType *toTuple,
SmallVectorImpl<unsigned> &sources) {
const unsigned unassigned = -1;
auto fromElts = fromTuple->getElements();
auto toElts = toTuple->getElements();
SmallVector<bool, 4> consumed(fromElts.size(), false);
sources.clear();
sources.assign(toElts.size(), unassigned);
// Match up any named elements.
for (unsigned i = 0, n = toElts.size(); i != n; ++i) {
const auto &toElt = toElts[i];
// Skip unnamed elements.
if (!toElt.hasName())
continue;
// Find the corresponding named element.
int matched = -1;
{
int index = 0;
for (auto field : fromElts) {
if (field.getName() == toElt.getName() && !consumed[index]) {
matched = index;
break;
}
++index;
}
}
if (matched == -1)
continue;
// Record this match.
sources[i] = matched;
consumed[matched] = true;
}
// Resolve any unmatched elements.
unsigned fromNext = 0, fromLast = fromElts.size();
auto skipToNextAvailableInput = [&] {
while (fromNext != fromLast && consumed[fromNext])
++fromNext;
};
skipToNextAvailableInput();
for (unsigned i = 0, n = toElts.size(); i != n; ++i) {
// Check whether we already found a value for this element.
if (sources[i] != unassigned)
continue;
// If there aren't any more inputs, we are done.
if (fromNext == fromLast) {
return true;
}
// Otherwise, assign this input to the next output element.
const auto &elt2 = toElts[i];
// Fail if the input element is named and we're trying to match it with
// something with a different label.
if (fromElts[fromNext].hasName() && elt2.hasName())
return true;
sources[i] = fromNext;
consumed[fromNext] = true;
skipToNextAvailableInput();
}
// Complain if we didn't reach the end of the inputs.
if (fromNext != fromLast) {
return true;
}
// If we got here, we should have claimed all the arguments.
assert(std::find(consumed.begin(), consumed.end(), false) == consumed.end());
return false;
}
Expr *ConstraintLocatorBuilder::trySimplifyToExpr() const {
SmallVector<LocatorPathElt, 4> pathBuffer;
auto anchor = getLocatorParts(pathBuffer);
// Locators are not guaranteed to have an anchor
// if constraint system is used to verify generic
// requirements.
if (!anchor.is<Expr *>())
return nullptr;
ArrayRef<LocatorPathElt> path = pathBuffer;
SourceRange range;
simplifyLocator(anchor, path, range);
return (path.empty() ? getAsExpr(anchor) : nullptr);
}
void ParentConditionalConformance::diagnoseConformanceStack(
DiagnosticEngine &diags, SourceLoc loc,
ArrayRef<ParentConditionalConformance> conformances) {
for (auto history : llvm::reverse(conformances)) {
diags.diagnose(loc, diag::requirement_implied_by_conditional_conformance,
history.ConformingType, history.Protocol->getDeclaredInterfaceType());
}
}
namespace {
/// Produce any additional syntactic diagnostics for the body of a function
/// that had a result builder applied.
class FunctionSyntacticDiagnosticWalker : public ASTWalker {
SmallVector<DeclContext *, 4> dcStack;
public:
FunctionSyntacticDiagnosticWalker(DeclContext *dc) { dcStack.push_back(dc); }
MacroWalking getMacroWalkingBehavior() const override {
return MacroWalking::Expansion;
}
PreWalkResult<Expr *> walkToExprPre(Expr *expr) override {
// We skip out-of-place expr checking here since we've already performed it.
performSyntacticExprDiagnostics(expr, dcStack.back(), /*ctp*/ std::nullopt,
/*isExprStmt=*/false,
/*disableAvailabilityChecking*/ false,
/*disableOutOfPlaceExprChecking*/ true);
if (auto closure = dyn_cast<ClosureExpr>(expr)) {
if (closure->isSeparatelyTypeChecked()) {
dcStack.push_back(closure);
return Action::Continue(expr);
}
}
return Action::SkipNode(expr);
}
PostWalkResult<Expr *> walkToExprPost(Expr *expr) override {
if (auto closure = dyn_cast<ClosureExpr>(expr)) {
if (closure->isSeparatelyTypeChecked()) {
assert(dcStack.back() == closure);
dcStack.pop_back();
}
}
return Action::Continue(expr);
}
PreWalkResult<Stmt *> walkToStmtPre(Stmt *stmt) override {
performStmtDiagnostics(stmt, dcStack.back());
return Action::Continue(stmt);
}
PreWalkResult<Pattern *> walkToPatternPre(Pattern *pattern) override {
return Action::SkipNode(pattern);
}
PreWalkAction walkToTypeReprPre(TypeRepr *typeRepr) override {
return Action::SkipNode();
}
PreWalkAction walkToParameterListPre(ParameterList *params) override {
return Action::SkipNode();
}
};
} // end anonymous namespace
void constraints::performSyntacticDiagnosticsForTarget(
const SyntacticElementTarget &target, bool isExprStmt,
bool disableExprAvailabilityChecking) {
auto *dc = target.getDeclContext();
switch (target.kind) {
case SyntacticElementTarget::Kind::expression: {
// First emit diagnostics for the main expression.
performSyntacticExprDiagnostics(
target.getAsExpr(), dc, target.getExprContextualTypePurpose(),
isExprStmt, disableExprAvailabilityChecking);
return;
}
case SyntacticElementTarget::Kind::forEachPreamble: {
auto *stmt = target.getAsForEachStmt();
// First emit diagnostics for the main expression.
performSyntacticExprDiagnostics(stmt->getTypeCheckedSequence(), dc,
CTP_ForEachSequence, isExprStmt,
disableExprAvailabilityChecking);
if (auto *whereExpr = stmt->getWhere())
performSyntacticExprDiagnostics(whereExpr, dc, CTP_Condition,
/*isExprStmt*/ false);
return;
}
case SyntacticElementTarget::Kind::function: {
// Check for out of place expressions. This needs to be done on the entire
// function body rather than on individual expressions since we need the
// context of the parent nodes.
auto *body = target.getFunctionBody();
diagnoseOutOfPlaceExprs(dc->getASTContext(), body,
/*contextualPurpose*/ std::nullopt);
FunctionSyntacticDiagnosticWalker walker(dc);
body->walk(walker);
return;
}
case SyntacticElementTarget::Kind::closure:
case SyntacticElementTarget::Kind::stmtCondition:
case SyntacticElementTarget::Kind::caseLabelItem:
case SyntacticElementTarget::Kind::patternBinding:
case SyntacticElementTarget::Kind::uninitializedVar:
// Nothing to do for these.
return;
}
llvm_unreachable("Unhandled case in switch!");
}
#pragma mark High-level entry points
Type TypeChecker::typeCheckExpression(Expr *&expr, DeclContext *dc,
ContextualTypeInfo contextualInfo,
TypeCheckExprOptions options) {
SyntacticElementTarget target(
expr, dc, contextualInfo.purpose, contextualInfo.getType(),
options.contains(TypeCheckExprFlags::IsDiscarded));
auto resultTarget = typeCheckExpression(target, options);
if (!resultTarget) {
expr = target.getAsExpr();
return Type();
}
expr = resultTarget->getAsExpr();
return expr->getType();
}
/// FIXME: In order to remote this function both \c FrontendStatsTracer
/// and \c PrettyStackTrace* have to be updated to accept `ASTNode`
// instead of each individual syntactic element types.
std::optional<SyntacticElementTarget>
TypeChecker::typeCheckExpression(SyntacticElementTarget &target,
TypeCheckExprOptions options) {
DeclContext *dc = target.getDeclContext();
auto &Context = dc->getASTContext();
FrontendStatsTracer StatsTracer(Context.Stats, "typecheck-expr",
target.getAsExpr());
PrettyStackTraceExpr stackTrace(Context, "type-checking", target.getAsExpr());
return typeCheckTarget(target, options);
}
std::optional<SyntacticElementTarget>
TypeChecker::typeCheckTarget(SyntacticElementTarget &target,
TypeCheckExprOptions options) {
auto errorResult = [&]() -> std::optional<SyntacticElementTarget> {
// Fill in ErrorTypes for the target if we can.
if (!options.contains(TypeCheckExprFlags::AvoidInvalidatingAST))
target.markInvalid();
return std::nullopt;
};
DeclContext *dc = target.getDeclContext();
auto &Context = dc->getASTContext();
PrettyStackTraceLocation stackTrace(Context, "type-checking-target",
target.getLoc());
// First, pre-check the target, validating any types that occur in the
// expression and folding sequence expressions.
if (ConstraintSystem::preCheckTarget(
target, /*replaceInvalidRefsWithErrors=*/true)) {
return errorResult();
}
// Check whether given target has a code completion token which requires
// special handling. Returns true if handled, in which case we've already
// type-checked it for completion, and don't need the solution applied.
if (Context.CompletionCallback &&
typeCheckForCodeCompletion(target, /*needsPrecheck*/ false,
[&](const constraints::Solution &S) {
Context.CompletionCallback->sawSolution(S);
}))
return std::nullopt;
// Construct a constraint system from this expression.
ConstraintSystemOptions csOptions = ConstraintSystemFlags::AllowFixes;
if (DiagnosticSuppression::isEnabled(Context.Diags))
csOptions |= ConstraintSystemFlags::SuppressDiagnostics;
if (options.contains(TypeCheckExprFlags::DisableMacroExpansions))
csOptions |= ConstraintSystemFlags::DisableMacroExpansions;
ConstraintSystem cs(dc, csOptions);
if (auto *expr = target.getAsExpr()) {
// Tell the constraint system what the contextual type is. This informs
// diagnostics and is a hint for various performance optimizations.
cs.setContextualInfo(expr, target.getExprContextualTypeInfo());
// Try to shrink the system by reducing disjunction domains. This
// goes through every sub-expression and generate its own sub-system, to
// try to reduce the domains of those subexpressions.
cs.shrink(expr);
target.setExpr(expr);
}
// If the client can handle unresolved type variables, leave them in the
// system.
auto allowFreeTypeVariables = FreeTypeVariableBinding::Disallow;
// Attempt to solve the constraint system.
auto viable = cs.solve(target, allowFreeTypeVariables);
if (!viable)
return errorResult();
// Apply this solution to the constraint system.
// FIXME: This shouldn't be necessary.
auto &solution = (*viable)[0];
cs.applySolution(solution);
// Apply the solution to the expression.
auto resultTarget = cs.applySolution(solution, target);
if (!resultTarget) {
// Failure already diagnosed, above, as part of applying the solution.
return errorResult();
}
// Unless the client has disabled them, perform syntactic checks on the
// expression now.
if (!cs.shouldSuppressDiagnostics()) {
bool isExprStmt = options.contains(TypeCheckExprFlags::IsExprStmt);
performSyntacticDiagnosticsForTarget(
*resultTarget, isExprStmt,
options.contains(TypeCheckExprFlags::DisableExprAvailabilityChecking));
}
return *resultTarget;
}
Type TypeChecker::typeCheckParameterDefault(Expr *&defaultValue,
DeclContext *DC, Type paramType,
bool isAutoClosure,
bool atCallerSide) {
// During normal type checking we don't type check the parameter default if
// the param has an error type. For code completion, we also type check the
// parameter default because it might contain the code completion token.
assert(paramType &&
(!paramType->hasError() || DC->getASTContext().CompletionCallback));
auto &ctx = DC->getASTContext();
// First, let's try to type-check default expression using interface
// type of the parameter, if that succeeds - we are done.
SyntacticElementTarget defaultExprTarget(
defaultValue, DC,
isAutoClosure ? CTP_AutoclosureDefaultParameter : CTP_DefaultParameter,
paramType, /*isDiscarded=*/false);
auto paramInterfaceTy = paramType->mapTypeOutOfContext();
{
// Buffer all of the diagnostics produced by \c typeCheckExpression
// since in some cases we need to try type-checking again with a
// different contextual type, see below.
DiagnosticTransaction diagnostics(ctx.Diags);
TypeCheckExprOptions options;
// Avoid invalidating the AST since we'll fall through and try to type-check
// with an archetype contextual type opened. Note we also don't need to call
// `markInvalid` for the target below since we'll replace the expression
// with an ErrorExpr on failure anyway.
options |= TypeCheckExprFlags::AvoidInvalidatingAST;
// Expand macro expansion expression at caller side only
if (!atCallerSide && isa<MacroExpansionExpr>(defaultValue)) {
options |= TypeCheckExprFlags::DisableMacroExpansions;
}
// First, let's try to type-check default expression using
// archetypes, which guarantees that it would work for any
// substitution of the generic parameter (if they are involved).
if (auto result = typeCheckExpression(defaultExprTarget, options)) {
defaultValue = result->getAsExpr();
return defaultValue->getType();
}
// Caller-side defaults are always type-checked based on the concrete
// type of the argument deduced at a particular call site.
if (isa<MagicIdentifierLiteralExpr>(defaultValue))
return Type();
// Parameter type doesn't have any generic parameters mentioned
// in it, so there is nothing to infer.
if (!paramInterfaceTy->hasTypeParameter())
return Type();
// Ignore any diagnostics emitted by the original type-check.
diagnostics.abort();
}
// Let's see whether it would be possible to use default expression
// for generic parameter inference.
//
// First, let's check whether:
// - Parameter type is a generic parameter; and
// - It's only used in the current position in the parameter list
// or result. This check makes sure that generic argument
// could only come from an explicit argument or this expression.
//
// If both of aforementioned conditions are true, let's attempt
// to open generic parameter and infer the type of this default
// expression.
OpenedTypeMap genericParameters;
ConstraintSystemOptions options;
options |= ConstraintSystemFlags::AllowFixes;
ConstraintSystem cs(DC, options);
auto *locator = cs.getConstraintLocator(
defaultValue, LocatorPathElt::ContextualType(
defaultExprTarget.getExprContextualTypePurpose()));
auto getCanonicalGenericParamTy = [](GenericTypeParamType *GP) {
return cast<GenericTypeParamType>(GP->getCanonicalType());
};
// Find and open all of the generic parameters used by the parameter
// and replace them with type variables.
auto contextualTy = paramInterfaceTy.transform([&](Type type) -> Type {
assert(!type->is<UnboundGenericType>());
if (auto *GP = type->getAs<GenericTypeParamType>()) {
auto openedVar = genericParameters.find(getCanonicalGenericParamTy(GP));
if (openedVar != genericParameters.end()) {
return openedVar->second;
}
return cs.openGenericParameter(DC->getParent(), GP, genericParameters,
locator);
}
return type;
});
auto containsTypes = [&](Type type, OpenedTypeMap &toFind) {
return type.findIf([&](Type nested) {
if (auto *GP = nested->getAs<GenericTypeParamType>())
return toFind.count(getCanonicalGenericParamTy(GP)) > 0;
return false;
});
};
auto containsGenericParamsExcluding = [&](Type type,
OpenedTypeMap &exclusions) -> bool {
return type.findIf([&](Type type) {
if (auto *GP = type->getAs<GenericTypeParamType>())
return !exclusions.count(getCanonicalGenericParamTy(GP));
return false;
});
};
// Anchor of this default expression i.e. function, subscript
// or enum case.
auto *anchor = cast<ValueDecl>(DC->getParent()->getAsDecl());
// Check whether generic parameters are only mentioned once in
// the anchor's signature.
{
auto anchorTy = anchor->getInterfaceType()->castTo<GenericFunctionType>();
// Reject if generic parameters are used in multiple different positions
// in the parameter list.
llvm::SmallVector<unsigned, 2> affectedParams;
for (unsigned i : indices(anchorTy->getParams())) {
const auto ¶m = anchorTy->getParams()[i];
if (containsTypes(param.getPlainType(), genericParameters))
affectedParams.push_back(i);
}
if (affectedParams.size() > 1) {
SmallString<32> paramBuf;
llvm::raw_svector_ostream params(paramBuf);
interleave(
affectedParams, [&](const unsigned index) { params << "#" << index; },
[&] { params << ", "; });
ctx.Diags.diagnose(
defaultValue->getLoc(),
diag::
cannot_default_generic_parameter_inferrable_from_another_parameter,
paramInterfaceTy, params.str());
return Type();
}
}
auto signature = DC->getGenericSignatureOfContext();
assert(signature && "generic parameter without signature?");
auto *requirementBaseLocator = cs.getConstraintLocator(
locator, LocatorPathElt::OpenedGeneric(signature));
// Let's check all of the requirements this parameter is involved in,
// If it's connected to any other generic types (directly or through
// a dependent member type), that means it could be inferred through
// them e.g. `T: X.Y` or `T == U`.
{
auto recordRequirement = [&](unsigned index, Requirement requirement,
ConstraintLocator *locator) {
cs.openGenericRequirement(DC->getParent(), index, requirement,
/*skipSelfProtocolConstraint=*/false, locator,
[&](Type type) -> Type {
return cs.openType(type, genericParameters,
locator);
});
};
auto diagnoseInvalidRequirement = [&](Requirement requirement) {
SmallString<32> reqBuf;
llvm::raw_svector_ostream req(reqBuf);
requirement.print(req, PrintOptions());
ctx.Diags.diagnose(
defaultValue->getLoc(),
diag::cannot_default_generic_parameter_invalid_requirement,
paramInterfaceTy, req.str());
};
auto requirements = signature.getRequirements();
for (unsigned reqIdx = 0; reqIdx != requirements.size(); ++reqIdx) {
auto &requirement = requirements[reqIdx];
switch (requirement.getKind()) {
case RequirementKind::SameShape:
llvm_unreachable("Same-shape requirement not supported here");
case RequirementKind::SameType: {
auto lhsTy = requirement.getFirstType();
auto rhsTy = requirement.getSecondType();
// Unrelated requirement.
if (!containsTypes(lhsTy, genericParameters) &&
!containsTypes(rhsTy, genericParameters))
continue;
// If both sides are dependent members, that's okay because types
// don't flow from member to the base e.g. `T.Element == U.Element`.
if (lhsTy->is<DependentMemberType>() &&
rhsTy->is<DependentMemberType>())
continue;
// Allow a subset of generic same-type requirements that only mention
// "in scope" generic parameters e.g. `T.X == Int` or `T == U.Z`
if (!containsGenericParamsExcluding(lhsTy, genericParameters) &&
!containsGenericParamsExcluding(rhsTy, genericParameters)) {
recordRequirement(reqIdx, requirement, requirementBaseLocator);
continue;
}
// If there is a same-type constraint that involves out of scope
// generic parameters mixed with in-scope ones, fail the type-check
// since the type could be inferred through other positions.
{
diagnoseInvalidRequirement(requirement);
return Type();
}
}
case RequirementKind::Conformance:
case RequirementKind::Superclass:
case RequirementKind::Layout:
auto adheringTy = requirement.getFirstType();
// Unrelated requirement.
if (!containsTypes(adheringTy, genericParameters))
continue;
// If adhering type has a mix or in- and out-of-scope parameters
// mentioned we need to diagnose.
if (containsGenericParamsExcluding(adheringTy, genericParameters)) {
diagnoseInvalidRequirement(requirement);
return Type();
}
if (requirement.getKind() == RequirementKind::Superclass) {
auto superclassTy = requirement.getSecondType();
if (containsGenericParamsExcluding(superclassTy, genericParameters)) {
diagnoseInvalidRequirement(requirement);
return Type();
}
}
recordRequirement(reqIdx, requirement, requirementBaseLocator);
break;
}
}
}
defaultExprTarget.setExprConversionType(contextualTy);
cs.setContextualInfo(defaultValue,
defaultExprTarget.getExprContextualTypeInfo());
auto viable = cs.solve(defaultExprTarget, FreeTypeVariableBinding::Disallow);
if (!viable)
return Type();
auto &solution = (*viable)[0];
cs.applySolution(solution);
if (auto result = cs.applySolution(solution, defaultExprTarget)) {
// Perform syntactic diagnostics on the type-checked target.
performSyntacticDiagnosticsForTarget(*result, /*isExprStmt=*/false);
defaultValue = result->getAsExpr();
return defaultValue->getType();
}
return Type();
}
bool TypeChecker::typeCheckBinding(Pattern *&pattern, Expr *&initializer,
DeclContext *DC, Type patternType,
PatternBindingDecl *PBD,
unsigned patternNumber,
TypeCheckExprOptions options) {
SyntacticElementTarget target =
PBD ? SyntacticElementTarget::forInitialization(
initializer, patternType, PBD, patternNumber,
/*bindPatternVarsOneWay=*/false)
: SyntacticElementTarget::forInitialization(
initializer, DC, patternType, pattern,
/*bindPatternVarsOneWay=*/false);
// Type-check the initializer.
auto resultTarget = typeCheckExpression(target, options);
if (resultTarget) {
initializer = resultTarget->getAsExpr();
pattern = resultTarget->getInitializationPattern();
return false;
}
auto &Context = DC->getASTContext();
initializer = target.getAsExpr();
if (!initializer->getType())
initializer->setType(ErrorType::get(Context));
// Assign error types to the pattern and its variables, to prevent it from
// being referenced by the constraint system.
if (patternType->hasUnresolvedType() ||
patternType->hasPlaceholder() ||
patternType->hasUnboundGenericType()) {
pattern->setType(ErrorType::get(Context));
}
pattern->forEachVariable([&](VarDecl *var) {
// Don't change the type of a variable that we've been able to
// compute a type for.
if (var->hasInterfaceType() &&
!var->getTypeInContext()->hasUnboundGenericType() &&
!var->isInvalid())
return;
var->setInvalid();
});
return true;
}
bool TypeChecker::typeCheckPatternBinding(PatternBindingDecl *PBD,
unsigned patternNumber,
Type patternType,
TypeCheckExprOptions options) {
Pattern *pattern = PBD->getPattern(patternNumber);
Expr *init = PBD->getInit(patternNumber);
// Enter an initializer context if necessary.
PatternBindingInitializer *initContext = PBD->getInitContext(patternNumber);
DeclContext *DC = initContext ? initContext : PBD->getDeclContext();
// If we weren't given a pattern type, compute one now.
if (!patternType) {
if (pattern->hasType())
patternType = pattern->getType();
else {
auto contextualPattern = ContextualPattern::forRawPattern(pattern, DC);
patternType = typeCheckPattern(contextualPattern);
}
if (patternType->hasError()) {
PBD->setInvalid();
return true;
}
}
bool hadError = TypeChecker::typeCheckBinding(pattern, init, DC, patternType,
PBD, patternNumber, options);
if (!init) {
PBD->setInvalid();
return true;
}
PBD->setPattern(patternNumber, pattern);
PBD->setInit(patternNumber, init);
if (hadError)
PBD->setInvalid();
PBD->setInitializerChecked(patternNumber);
return hadError;
}
bool TypeChecker::typeCheckForEachPreamble(DeclContext *dc, ForEachStmt *stmt,
GenericEnvironment *packElementEnv) {
auto &Context = dc->getASTContext();
FrontendStatsTracer statsTracer(Context.Stats, "typecheck-for-each", stmt);
PrettyStackTraceStmt stackTrace(Context, "type-checking-for-each", stmt);
auto failed = [&]() -> bool {
// Invalidate the pattern and the var decl.
stmt->getPattern()->setType(ErrorType::get(Context));
stmt->getPattern()->forEachVariable([&](VarDecl *var) {
if (var->hasInterfaceType() && !var->isInvalid())
return;
var->setInvalid();
});
return true;
};
auto target = SyntacticElementTarget::forForEachPreamble(
stmt, dc, /*ignoreWhereClause=*/false, packElementEnv);
if (!typeCheckTarget(target))
return failed();
// Check to see if the sequence expr is throwing (in async context),
// if so require the stmt to have a `try`.
if (diagnoseUnhandledThrowsInAsyncContext(dc, stmt))
return failed();
return false;
}
bool TypeChecker::typeCheckCondition(Expr *&expr, DeclContext *dc) {
// If this expression is already typechecked and has type Bool, then just
// re-typecheck it.
if (expr->getType() && expr->getType()->isBool()) {
auto resultTy =
TypeChecker::typeCheckExpression(expr, dc);
return !resultTy;
}
auto *boolDecl = dc->getASTContext().getBoolDecl();
if (!boolDecl)
return true;
auto resultTy = TypeChecker::typeCheckExpression(
expr, dc,
/*contextualInfo=*/{boolDecl->getDeclaredInterfaceType(), CTP_Condition});
return !resultTy;
}
/// Find the `~=` operator that can compare an expression inside a pattern to a
/// value of a given type.
bool TypeChecker::typeCheckExprPattern(ExprPattern *EP, DeclContext *DC,
Type rhsType) {
auto &Context = DC->getASTContext();
FrontendStatsTracer StatsTracer(Context.Stats,
"typecheck-expr-pattern", EP);
PrettyStackTracePattern stackTrace(Context, "type-checking", EP);
EP->getMatchVar()->setInterfaceType(rhsType->mapTypeOutOfContext());
// Check the expression as a condition.
auto target = SyntacticElementTarget::forExprPattern(EP);
auto result = typeCheckExpression(target);
if (!result)
return true;
// Save the type-checked expression in the pattern.
EP->setMatchExpr(result->getAsExpr());
// Set the type on the pattern.
EP->setType(rhsType);