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luau/Analysis/src/ConstraintSolver.cpp
Andy Friesen d2ab5df62b
Sync to upstream/release/565 (#845) 
We've made a few small changes to reduce the amount of stack we use when
typechecking nested method calls (eg `foo:bar():baz():quux()`).

We've also fixed a small bytecode compiler issue that caused us to emit
redundant jump instructions in code that conditionally uses `break` or
`continue`.

On the new solver, we've switched to a new, better way to handle
augmentations to unsealed tables. We've also made some substantial
improvements to type inference and error reporting on function calls.
These things should both be on par with the old solver now.

The main improvements to the native code generator have been elimination
of some redundant type tag checks. Also, we are starting to inline
particular fastcalls directly to IR.

---------

Co-authored-by: Arseny Kapoulkine <arseny.kapoulkine@gmail.com>
Co-authored-by: Vyacheslav Egorov <vegorov@roblox.com>
2023-02-24 13:49:38 -08:00

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// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#include "Luau/Anyification.h"
#include "Luau/ApplyTypeFunction.h"
#include "Luau/Clone.h"
#include "Luau/ConstraintSolver.h"
#include "Luau/DcrLogger.h"
#include "Luau/Instantiation.h"
#include "Luau/Location.h"
#include "Luau/Metamethods.h"
#include "Luau/ModuleResolver.h"
#include "Luau/Quantify.h"
#include "Luau/ToString.h"
#include "Luau/TypeUtils.h"
#include "Luau/Type.h"
#include "Luau/Unifier.h"
#include "Luau/VisitType.h"
LUAU_FASTFLAGVARIABLE(DebugLuauLogSolver, false);
LUAU_FASTFLAGVARIABLE(DebugLuauLogSolverToJson, false);
namespace Luau
{
size_t HashBlockedConstraintId::operator()(const BlockedConstraintId& bci) const
{
size_t result = 0;
if (const TypeId* ty = get_if<TypeId>(&bci))
result = std::hash<TypeId>()(*ty);
else if (const TypePackId* tp = get_if<TypePackId>(&bci))
result = std::hash<TypePackId>()(*tp);
else if (Constraint const* const* c = get_if<const Constraint*>(&bci))
result = std::hash<const Constraint*>()(*c);
else
LUAU_ASSERT(!"Should be unreachable");
return result;
}
[[maybe_unused]] static void dumpBindings(NotNull<Scope> scope, ToStringOptions& opts)
{
for (const auto& [k, v] : scope->bindings)
{
auto d = toString(v.typeId, opts);
printf("\t%s : %s\n", k.c_str(), d.c_str());
}
for (NotNull<Scope> child : scope->children)
dumpBindings(child, opts);
}
static std::pair<std::vector<TypeId>, std::vector<TypePackId>> saturateArguments(TypeArena* arena, NotNull<BuiltinTypes> builtinTypes,
const TypeFun& fn, const std::vector<TypeId>& rawTypeArguments, const std::vector<TypePackId>& rawPackArguments)
{
std::vector<TypeId> saturatedTypeArguments;
std::vector<TypeId> extraTypes;
std::vector<TypePackId> saturatedPackArguments;
for (size_t i = 0; i < rawTypeArguments.size(); ++i)
{
TypeId ty = rawTypeArguments[i];
if (i < fn.typeParams.size())
saturatedTypeArguments.push_back(ty);
else
extraTypes.push_back(ty);
}
// If we collected extra types, put them in a type pack now. This case is
// mutually exclusive with the type pack -> type conversion we do below:
// extraTypes will only have elements in it if we have more types than we
// have parameter slots for them to go into.
if (!extraTypes.empty())
{
saturatedPackArguments.push_back(arena->addTypePack(extraTypes));
}
for (size_t i = 0; i < rawPackArguments.size(); ++i)
{
TypePackId tp = rawPackArguments[i];
// If we are short on regular type saturatedTypeArguments and we have a single
// element type pack, we can decompose that to the type it contains and
// use that as a type parameter.
if (saturatedTypeArguments.size() < fn.typeParams.size() && size(tp) == 1 && finite(tp) && first(tp) && saturatedPackArguments.empty())
{
saturatedTypeArguments.push_back(*first(tp));
}
else
{
saturatedPackArguments.push_back(tp);
}
}
size_t typesProvided = saturatedTypeArguments.size();
size_t typesRequired = fn.typeParams.size();
size_t packsProvided = saturatedPackArguments.size();
size_t packsRequired = fn.typePackParams.size();
// Extra types should be accumulated in extraTypes, not saturatedTypeArguments. Extra
// packs will be accumulated in saturatedPackArguments, so we don't have an
// assertion for that.
LUAU_ASSERT(typesProvided <= typesRequired);
// If we didn't provide enough types, but we did provide a type pack, we
// don't want to use defaults. The rationale for this is that if the user
// provides a pack but doesn't provide enough types, we want to report an
// error, rather than simply using the default saturatedTypeArguments, if they exist. If
// they did provide enough types, but not enough packs, we of course want to
// use the default packs.
bool needsDefaults = (typesProvided < typesRequired && packsProvided == 0) || (typesProvided == typesRequired && packsProvided < packsRequired);
if (needsDefaults)
{
// Default types can reference earlier types. It's legal to write
// something like
// type T<A, B = A> = (A, B) -> number
// and we need to respect that. We use an ApplyTypeFunction for this.
ApplyTypeFunction atf{arena};
for (size_t i = 0; i < typesProvided; ++i)
atf.typeArguments[fn.typeParams[i].ty] = saturatedTypeArguments[i];
for (size_t i = typesProvided; i < typesRequired; ++i)
{
TypeId defaultTy = fn.typeParams[i].defaultValue.value_or(nullptr);
// We will fill this in with the error type later.
if (!defaultTy)
break;
TypeId instantiatedDefault = atf.substitute(defaultTy).value_or(builtinTypes->errorRecoveryType());
atf.typeArguments[fn.typeParams[i].ty] = instantiatedDefault;
saturatedTypeArguments.push_back(instantiatedDefault);
}
for (size_t i = 0; i < packsProvided; ++i)
{
atf.typePackArguments[fn.typePackParams[i].tp] = saturatedPackArguments[i];
}
for (size_t i = packsProvided; i < packsRequired; ++i)
{
TypePackId defaultTp = fn.typePackParams[i].defaultValue.value_or(nullptr);
// We will fill this in with the error type pack later.
if (!defaultTp)
break;
TypePackId instantiatedDefault = atf.substitute(defaultTp).value_or(builtinTypes->errorRecoveryTypePack());
atf.typePackArguments[fn.typePackParams[i].tp] = instantiatedDefault;
saturatedPackArguments.push_back(instantiatedDefault);
}
}
// If we didn't create an extra type pack from overflowing parameter packs,
// and we're still missing a type pack, plug in an empty type pack as the
// value of the empty packs.
if (extraTypes.empty() && saturatedPackArguments.size() + 1 == fn.typePackParams.size())
{
saturatedPackArguments.push_back(arena->addTypePack({}));
}
// We need to have _something_ when we substitute the generic saturatedTypeArguments,
// even if they're missing, so we use the error type as a filler.
for (size_t i = saturatedTypeArguments.size(); i < typesRequired; ++i)
{
saturatedTypeArguments.push_back(builtinTypes->errorRecoveryType());
}
for (size_t i = saturatedPackArguments.size(); i < packsRequired; ++i)
{
saturatedPackArguments.push_back(builtinTypes->errorRecoveryTypePack());
}
// At this point, these two conditions should be true. If they aren't we
// will run into access violations.
LUAU_ASSERT(saturatedTypeArguments.size() == fn.typeParams.size());
LUAU_ASSERT(saturatedPackArguments.size() == fn.typePackParams.size());
return {saturatedTypeArguments, saturatedPackArguments};
}
bool InstantiationSignature::operator==(const InstantiationSignature& rhs) const
{
return fn == rhs.fn && arguments == rhs.arguments && packArguments == rhs.packArguments;
}
size_t HashInstantiationSignature::operator()(const InstantiationSignature& signature) const
{
size_t hash = std::hash<TypeId>{}(signature.fn.type);
for (const GenericTypeDefinition& p : signature.fn.typeParams)
{
hash ^= (std::hash<TypeId>{}(p.ty) << 1);
}
for (const GenericTypePackDefinition& p : signature.fn.typePackParams)
{
hash ^= (std::hash<TypePackId>{}(p.tp) << 1);
}
for (const TypeId a : signature.arguments)
{
hash ^= (std::hash<TypeId>{}(a) << 1);
}
for (const TypePackId a : signature.packArguments)
{
hash ^= (std::hash<TypePackId>{}(a) << 1);
}
return hash;
}
void dump(ConstraintSolver* cs, ToStringOptions& opts)
{
printf("constraints:\n");
for (NotNull<const Constraint> c : cs->unsolvedConstraints)
{
auto it = cs->blockedConstraints.find(c);
int blockCount = it == cs->blockedConstraints.end() ? 0 : int(it->second);
printf("\t%d\t%s\n", blockCount, toString(*c, opts).c_str());
for (NotNull<Constraint> dep : c->dependencies)
{
auto unsolvedIter = std::find(begin(cs->unsolvedConstraints), end(cs->unsolvedConstraints), dep);
if (unsolvedIter == cs->unsolvedConstraints.end())
continue;
auto it = cs->blockedConstraints.find(dep);
int blockCount = it == cs->blockedConstraints.end() ? 0 : int(it->second);
printf("\t%d\t\t%s\n", blockCount, toString(*dep, opts).c_str());
}
}
}
ConstraintSolver::ConstraintSolver(NotNull<Normalizer> normalizer, NotNull<Scope> rootScope, std::vector<NotNull<Constraint>> constraints,
ModuleName moduleName, NotNull<TypeReduction> reducer, NotNull<ModuleResolver> moduleResolver, std::vector<RequireCycle> requireCycles,
DcrLogger* logger)
: arena(normalizer->arena)
, builtinTypes(normalizer->builtinTypes)
, normalizer(normalizer)
, reducer(reducer)
, constraints(std::move(constraints))
, rootScope(rootScope)
, currentModuleName(std::move(moduleName))
, moduleResolver(moduleResolver)
, requireCycles(requireCycles)
, logger(logger)
{
opts.exhaustive = true;
for (NotNull<Constraint> c : this->constraints)
{
unsolvedConstraints.push_back(c);
for (NotNull<const Constraint> dep : c->dependencies)
{
block(dep, c);
}
}
if (FFlag::DebugLuauLogSolverToJson)
LUAU_ASSERT(logger);
}
void ConstraintSolver::randomize(unsigned seed)
{
if (unsolvedConstraints.empty())
return;
unsigned int rng = seed;
for (size_t i = unsolvedConstraints.size() - 1; i > 0; --i)
{
// Fisher-Yates shuffle
size_t j = rng % (i + 1);
std::swap(unsolvedConstraints[i], unsolvedConstraints[j]);
// LCG RNG, constants from Numerical Recipes
// This may occasionally result in skewed shuffles due to distribution properties, but this is a debugging tool so it should be good enough
rng = rng * 1664525 + 1013904223;
}
}
void ConstraintSolver::run()
{
if (isDone())
return;
if (FFlag::DebugLuauLogSolver)
{
printf("Starting solver\n");
dump(this, opts);
printf("Bindings:\n");
dumpBindings(rootScope, opts);
}
if (FFlag::DebugLuauLogSolverToJson)
{
logger->captureInitialSolverState(rootScope, unsolvedConstraints);
}
auto runSolverPass = [&](bool force) {
bool progress = false;
size_t i = 0;
while (i < unsolvedConstraints.size())
{
NotNull<const Constraint> c = unsolvedConstraints[i];
if (!force && isBlocked(c))
{
++i;
continue;
}
std::string saveMe = FFlag::DebugLuauLogSolver ? toString(*c, opts) : std::string{};
StepSnapshot snapshot;
if (FFlag::DebugLuauLogSolverToJson)
{
snapshot = logger->prepareStepSnapshot(rootScope, c, force, unsolvedConstraints);
}
bool success = tryDispatch(c, force);
progress |= success;
if (success)
{
unblock(c);
unsolvedConstraints.erase(unsolvedConstraints.begin() + i);
if (FFlag::DebugLuauLogSolverToJson)
{
logger->commitStepSnapshot(snapshot);
}
if (FFlag::DebugLuauLogSolver)
{
if (force)
printf("Force ");
printf("Dispatched\n\t%s\n", saveMe.c_str());
if (force)
{
printf("Blocked on:\n");
for (const auto& [bci, cv] : blocked)
{
if (end(cv) == std::find(begin(cv), end(cv), c))
continue;
if (auto bty = get_if<TypeId>(&bci))
printf("\tType %s\n", toString(*bty, opts).c_str());
else if (auto btp = get_if<TypePackId>(&bci))
printf("\tPack %s\n", toString(*btp, opts).c_str());
else if (auto cc = get_if<const Constraint*>(&bci))
printf("\tCons %s\n", toString(**cc, opts).c_str());
else
LUAU_ASSERT(!"Unreachable??");
}
}
dump(this, opts);
}
}
else
++i;
if (force && success)
return true;
}
return progress;
};
bool progress = false;
do
{
progress = runSolverPass(false);
if (!progress)
progress |= runSolverPass(true);
} while (progress);
finalizeModule();
if (FFlag::DebugLuauLogSolver)
{
dumpBindings(rootScope, opts);
}
if (FFlag::DebugLuauLogSolverToJson)
{
logger->captureFinalSolverState(rootScope, unsolvedConstraints);
}
}
bool ConstraintSolver::isDone()
{
return unsolvedConstraints.empty();
}
void ConstraintSolver::finalizeModule()
{
Anyification a{arena, rootScope, builtinTypes, &iceReporter, builtinTypes->anyType, builtinTypes->anyTypePack};
std::optional<TypePackId> returnType = a.substitute(rootScope->returnType);
if (!returnType)
{
reportError(CodeTooComplex{}, Location{});
rootScope->returnType = builtinTypes->errorTypePack;
}
else
rootScope->returnType = *returnType;
}
bool ConstraintSolver::tryDispatch(NotNull<const Constraint> constraint, bool force)
{
if (!force && isBlocked(constraint))
return false;
bool success = false;
if (auto sc = get<SubtypeConstraint>(*constraint))
success = tryDispatch(*sc, constraint, force);
else if (auto psc = get<PackSubtypeConstraint>(*constraint))
success = tryDispatch(*psc, constraint, force);
else if (auto gc = get<GeneralizationConstraint>(*constraint))
success = tryDispatch(*gc, constraint, force);
else if (auto ic = get<InstantiationConstraint>(*constraint))
success = tryDispatch(*ic, constraint, force);
else if (auto uc = get<UnaryConstraint>(*constraint))
success = tryDispatch(*uc, constraint, force);
else if (auto bc = get<BinaryConstraint>(*constraint))
success = tryDispatch(*bc, constraint, force);
else if (auto ic = get<IterableConstraint>(*constraint))
success = tryDispatch(*ic, constraint, force);
else if (auto nc = get<NameConstraint>(*constraint))
success = tryDispatch(*nc, constraint);
else if (auto taec = get<TypeAliasExpansionConstraint>(*constraint))
success = tryDispatch(*taec, constraint);
else if (auto fcc = get<FunctionCallConstraint>(*constraint))
success = tryDispatch(*fcc, constraint);
else if (auto fcc = get<PrimitiveTypeConstraint>(*constraint))
success = tryDispatch(*fcc, constraint);
else if (auto hpc = get<HasPropConstraint>(*constraint))
success = tryDispatch(*hpc, constraint);
else if (auto spc = get<SetPropConstraint>(*constraint))
success = tryDispatch(*spc, constraint, force);
else if (auto spc = get<SetIndexerConstraint>(*constraint))
success = tryDispatch(*spc, constraint, force);
else if (auto sottc = get<SingletonOrTopTypeConstraint>(*constraint))
success = tryDispatch(*sottc, constraint);
else if (auto uc = get<UnpackConstraint>(*constraint))
success = tryDispatch(*uc, constraint);
else
LUAU_ASSERT(false);
if (success)
unblock(constraint);
return success;
}
bool ConstraintSolver::tryDispatch(const SubtypeConstraint& c, NotNull<const Constraint> constraint, bool force)
{
if (isBlocked(c.subType))
return block(c.subType, constraint);
else if (isBlocked(c.superType))
return block(c.superType, constraint);
Unifier u{normalizer, Mode::Strict, constraint->scope, Location{}, Covariant};
u.useScopes = true;
u.tryUnify(c.subType, c.superType);
if (!u.blockedTypes.empty() || !u.blockedTypePacks.empty())
{
for (TypeId bt : u.blockedTypes)
block(bt, constraint);
for (TypePackId btp : u.blockedTypePacks)
block(btp, constraint);
return false;
}
if (!u.errors.empty())
{
TypeId errorType = errorRecoveryType();
u.tryUnify(c.subType, errorType);
u.tryUnify(c.superType, errorType);
}
const auto [changedTypes, changedPacks] = u.log.getChanges();
u.log.commit();
unblock(changedTypes);
unblock(changedPacks);
// unify(c.subType, c.superType, constraint->scope);
return true;
}
bool ConstraintSolver::tryDispatch(const PackSubtypeConstraint& c, NotNull<const Constraint> constraint, bool force)
{
if (isBlocked(c.subPack))
return block(c.subPack, constraint);
else if (isBlocked(c.superPack))
return block(c.superPack, constraint);
unify(c.subPack, c.superPack, constraint->scope);
return true;
}
bool ConstraintSolver::tryDispatch(const GeneralizationConstraint& c, NotNull<const Constraint> constraint, bool force)
{
if (isBlocked(c.sourceType))
return block(c.sourceType, constraint);
TypeId generalized = quantify(arena, c.sourceType, constraint->scope);
if (isBlocked(c.generalizedType))
asMutable(c.generalizedType)->ty.emplace<BoundType>(generalized);
else
unify(c.generalizedType, generalized, constraint->scope);
unblock(c.generalizedType);
unblock(c.sourceType);
return true;
}
bool ConstraintSolver::tryDispatch(const InstantiationConstraint& c, NotNull<const Constraint> constraint, bool force)
{
if (isBlocked(c.superType))
return block(c.superType, constraint);
Instantiation inst(TxnLog::empty(), arena, TypeLevel{}, constraint->scope);
std::optional<TypeId> instantiated = inst.substitute(c.superType);
LUAU_ASSERT(instantiated); // TODO FIXME HANDLE THIS
if (isBlocked(c.subType))
asMutable(c.subType)->ty.emplace<BoundType>(*instantiated);
else
unify(c.subType, *instantiated, constraint->scope);
unblock(c.subType);
return true;
}
bool ConstraintSolver::tryDispatch(const UnaryConstraint& c, NotNull<const Constraint> constraint, bool force)
{
TypeId operandType = follow(c.operandType);
if (isBlocked(operandType))
return block(operandType, constraint);
if (get<FreeType>(operandType))
return block(operandType, constraint);
LUAU_ASSERT(get<BlockedType>(c.resultType));
switch (c.op)
{
case AstExprUnary::Not:
{
asMutable(c.resultType)->ty.emplace<BoundType>(builtinTypes->booleanType);
return true;
}
case AstExprUnary::Len:
{
// __len must return a number.
asMutable(c.resultType)->ty.emplace<BoundType>(builtinTypes->numberType);
return true;
}
case AstExprUnary::Minus:
{
if (isNumber(operandType) || get<AnyType>(operandType) || get<ErrorType>(operandType) || get<NeverType>(operandType))
{
asMutable(c.resultType)->ty.emplace<BoundType>(c.operandType);
}
else if (std::optional<TypeId> mm = findMetatableEntry(builtinTypes, errors, operandType, "__unm", constraint->location))
{
TypeId mmTy = follow(*mm);
if (get<FreeType>(mmTy) && !force)
return block(mmTy, constraint);
TypePackId argPack = arena->addTypePack(TypePack{{operandType}, {}});
TypePackId retPack = arena->addTypePack(BlockedTypePack{});
asMutable(c.resultType)->ty.emplace<FreeType>(constraint->scope);
pushConstraint(constraint->scope, constraint->location, PackSubtypeConstraint{retPack, arena->addTypePack(TypePack{{c.resultType}})});
pushConstraint(constraint->scope, constraint->location, FunctionCallConstraint{mmTy, argPack, retPack, nullptr});
}
else
{
asMutable(c.resultType)->ty.emplace<BoundType>(builtinTypes->errorRecoveryType());
}
return true;
}
}
LUAU_ASSERT(false);
return false;
}
bool ConstraintSolver::tryDispatch(const BinaryConstraint& c, NotNull<const Constraint> constraint, bool force)
{
TypeId leftType = follow(c.leftType);
TypeId rightType = follow(c.rightType);
TypeId resultType = follow(c.resultType);
bool isLogical = c.op == AstExprBinary::Op::And || c.op == AstExprBinary::Op::Or;
/* Compound assignments create constraints of the form
*
* A <: Binary<op, A, B>
*
* This constraint is the one that is meant to unblock A, so it doesn't
* make any sense to stop and wait for someone else to do it.
*/
if (isBlocked(leftType) && leftType != resultType)
return block(c.leftType, constraint);
if (isBlocked(rightType) && rightType != resultType)
return block(c.rightType, constraint);
if (!force)
{
// Logical expressions may proceed if the LHS is free.
if (get<FreeType>(leftType) && !isLogical)
return block(leftType, constraint);
}
// Logical expressions may proceed if the LHS is free.
if (isBlocked(leftType) || (get<FreeType>(leftType) && !isLogical))
{
asMutable(resultType)->ty.emplace<BoundType>(errorRecoveryType());
unblock(resultType);
return true;
}
// Metatables go first, even if there is primitive behavior.
if (auto it = kBinaryOpMetamethods.find(c.op); it != kBinaryOpMetamethods.end())
{
// Metatables are not the same. The metamethod will not be invoked.
if ((c.op == AstExprBinary::Op::CompareEq || c.op == AstExprBinary::Op::CompareNe) &&
getMetatable(leftType, builtinTypes) != getMetatable(rightType, builtinTypes))
{
// TODO: Boolean singleton false? The result is _always_ boolean false.
asMutable(resultType)->ty.emplace<BoundType>(builtinTypes->booleanType);
unblock(resultType);
return true;
}
std::optional<TypeId> mm;
// The LHS metatable takes priority over the RHS metatable, where
// present.
if (std::optional<TypeId> leftMm = findMetatableEntry(builtinTypes, errors, leftType, it->second, constraint->location))
mm = leftMm;
else if (std::optional<TypeId> rightMm = findMetatableEntry(builtinTypes, errors, rightType, it->second, constraint->location))
mm = rightMm;
if (mm)
{
Instantiation instantiation{TxnLog::empty(), arena, TypeLevel{}, constraint->scope};
std::optional<TypeId> instantiatedMm = instantiation.substitute(*mm);
if (!instantiatedMm)
{
reportError(CodeTooComplex{}, constraint->location);
return true;
}
// TODO: Is a table with __call legal here?
// TODO: Overloads
if (const FunctionType* ftv = get<FunctionType>(follow(*instantiatedMm)))
{
TypePackId inferredArgs;
// For >= and > we invoke __lt and __le respectively with
// swapped argument ordering.
if (c.op == AstExprBinary::Op::CompareGe || c.op == AstExprBinary::Op::CompareGt)
{
inferredArgs = arena->addTypePack({rightType, leftType});
}
else
{
inferredArgs = arena->addTypePack({leftType, rightType});
}
unify(inferredArgs, ftv->argTypes, constraint->scope);
TypeId mmResult;
// Comparison operations always evaluate to a boolean,
// regardless of what the metamethod returns.
switch (c.op)
{
case AstExprBinary::Op::CompareEq:
case AstExprBinary::Op::CompareNe:
case AstExprBinary::Op::CompareGe:
case AstExprBinary::Op::CompareGt:
case AstExprBinary::Op::CompareLe:
case AstExprBinary::Op::CompareLt:
mmResult = builtinTypes->booleanType;
break;
default:
mmResult = first(ftv->retTypes).value_or(errorRecoveryType());
}
asMutable(resultType)->ty.emplace<BoundType>(mmResult);
unblock(resultType);
(*c.astOriginalCallTypes)[c.astFragment] = *mm;
(*c.astOverloadResolvedTypes)[c.astFragment] = *instantiatedMm;
return true;
}
}
// If there's no metamethod available, fall back to primitive behavior.
}
// If any is present, the expression must evaluate to any as well.
bool leftAny = get<AnyType>(leftType) || get<ErrorType>(leftType);
bool rightAny = get<AnyType>(rightType) || get<ErrorType>(rightType);
bool anyPresent = leftAny || rightAny;
switch (c.op)
{
// For arithmetic operators, if the LHS is a number, the RHS must be a
// number as well. The result will also be a number.
case AstExprBinary::Op::Add:
case AstExprBinary::Op::Sub:
case AstExprBinary::Op::Mul:
case AstExprBinary::Op::Div:
case AstExprBinary::Op::Pow:
case AstExprBinary::Op::Mod:
if (isNumber(leftType))
{
unify(leftType, rightType, constraint->scope);
asMutable(resultType)->ty.emplace<BoundType>(anyPresent ? builtinTypes->anyType : leftType);
unblock(resultType);
return true;
}
break;
// For concatenation, if the LHS is a string, the RHS must be a string as
// well. The result will also be a string.
case AstExprBinary::Op::Concat:
if (isString(leftType))
{
unify(leftType, rightType, constraint->scope);
asMutable(resultType)->ty.emplace<BoundType>(anyPresent ? builtinTypes->anyType : leftType);
unblock(resultType);
return true;
}
break;
// Inexact comparisons require that the types be both numbers or both
// strings, and evaluate to a boolean.
case AstExprBinary::Op::CompareGe:
case AstExprBinary::Op::CompareGt:
case AstExprBinary::Op::CompareLe:
case AstExprBinary::Op::CompareLt:
if ((isNumber(leftType) && isNumber(rightType)) || (isString(leftType) && isString(rightType)))
{
asMutable(resultType)->ty.emplace<BoundType>(builtinTypes->booleanType);
unblock(resultType);
return true;
}
break;
// == and ~= always evaluate to a boolean, and impose no other constraints
// on their parameters.
case AstExprBinary::Op::CompareEq:
case AstExprBinary::Op::CompareNe:
asMutable(resultType)->ty.emplace<BoundType>(builtinTypes->booleanType);
unblock(resultType);
return true;
// And evalutes to a boolean if the LHS is falsey, and the RHS type if LHS is
// truthy.
case AstExprBinary::Op::And:
{
TypeId leftFilteredTy = arena->addType(IntersectionType{{builtinTypes->falsyType, leftType}});
asMutable(resultType)->ty.emplace<BoundType>(arena->addType(UnionType{{leftFilteredTy, rightType}}));
unblock(resultType);
return true;
}
// Or evaluates to the LHS type if the LHS is truthy, and the RHS type if
// LHS is falsey.
case AstExprBinary::Op::Or:
{
TypeId leftFilteredTy = arena->addType(IntersectionType{{builtinTypes->truthyType, leftType}});
asMutable(resultType)->ty.emplace<BoundType>(arena->addType(UnionType{{leftFilteredTy, rightType}}));
unblock(resultType);
return true;
}
default:
iceReporter.ice("Unhandled AstExprBinary::Op for binary operation", constraint->location);
break;
}
// We failed to either evaluate a metamethod or invoke primitive behavior.
unify(leftType, errorRecoveryType(), constraint->scope);
unify(rightType, errorRecoveryType(), constraint->scope);
asMutable(resultType)->ty.emplace<BoundType>(errorRecoveryType());
unblock(resultType);
return true;
}
bool ConstraintSolver::tryDispatch(const IterableConstraint& c, NotNull<const Constraint> constraint, bool force)
{
/*
* for .. in loops can play out in a bunch of different ways depending on
* the shape of iteratee.
*
* iteratee might be:
* * (nextFn)
* * (nextFn, table)
* * (nextFn, table, firstIndex)
* * table with a metatable and __index
* * table with a metatable and __call but no __index (if the metatable has
* both, __index takes precedence)
* * table with an indexer but no __index or __call (or no metatable)
*
* To dispatch this constraint, we need first to know enough about iteratee
* to figure out which of the above shapes we are actually working with.
*
* If `force` is true and we still do not know, we must flag a warning. Type
* families are the fix for this.
*
* Since we need to know all of this stuff about the types of the iteratee,
* we have no choice but for ConstraintSolver to also be the thing that
* applies constraints to the types of the iterators.
*/
auto block_ = [&](auto&& t) {
if (force)
{
// If we haven't figured out the type of the iteratee by now,
// there's nothing we can do.
return true;
}
block(t, constraint);
return false;
};
auto [iteratorTypes, iteratorTail] = flatten(c.iterator);
if (iteratorTail)
return block_(*iteratorTail);
{
bool blocked = false;
for (TypeId t : iteratorTypes)
{
if (isBlocked(t))
{
block(t, constraint);
blocked = true;
}
}
if (blocked)
return false;
}
if (0 == iteratorTypes.size())
{
Anyification anyify{arena, constraint->scope, builtinTypes, &iceReporter, errorRecoveryType(), errorRecoveryTypePack()};
std::optional<TypePackId> anyified = anyify.substitute(c.variables);
LUAU_ASSERT(anyified);
unify(*anyified, c.variables, constraint->scope);
return true;
}
TypeId nextTy = follow(iteratorTypes[0]);
if (get<FreeType>(nextTy))
return block_(nextTy);
if (get<FunctionType>(nextTy))
{
TypeId tableTy = builtinTypes->nilType;
if (iteratorTypes.size() >= 2)
tableTy = iteratorTypes[1];
TypeId firstIndexTy = builtinTypes->nilType;
if (iteratorTypes.size() >= 3)
firstIndexTy = iteratorTypes[2];
return tryDispatchIterableFunction(nextTy, tableTy, firstIndexTy, c, constraint, force);
}
else
return tryDispatchIterableTable(iteratorTypes[0], c, constraint, force);
return true;
}
bool ConstraintSolver::tryDispatch(const NameConstraint& c, NotNull<const Constraint> constraint)
{
if (isBlocked(c.namedType))
return block(c.namedType, constraint);
TypeId target = follow(c.namedType);
if (target->persistent || target->owningArena != arena)
return true;
if (TableType* ttv = getMutable<TableType>(target))
{
if (c.synthetic && !ttv->name)
ttv->syntheticName = c.name;
else
{
ttv->name = c.name;
ttv->instantiatedTypeParams = c.typeParameters;
ttv->instantiatedTypePackParams = c.typePackParameters;
}
}
else if (MetatableType* mtv = getMutable<MetatableType>(target))
mtv->syntheticName = c.name;
else if (get<IntersectionType>(target) || get<UnionType>(target))
{
// nothing (yet)
}
else
return block(c.namedType, constraint);
return true;
}
struct InfiniteTypeFinder : TypeOnceVisitor
{
ConstraintSolver* solver;
const InstantiationSignature& signature;
NotNull<Scope> scope;
bool foundInfiniteType = false;
explicit InfiniteTypeFinder(ConstraintSolver* solver, const InstantiationSignature& signature, NotNull<Scope> scope)
: solver(solver)
, signature(signature)
, scope(scope)
{
}
bool visit(TypeId ty, const PendingExpansionType& petv) override
{
std::optional<TypeFun> tf =
(petv.prefix) ? scope->lookupImportedType(petv.prefix->value, petv.name.value) : scope->lookupType(petv.name.value);
if (!tf.has_value())
return true;
auto [typeArguments, packArguments] = saturateArguments(solver->arena, solver->builtinTypes, *tf, petv.typeArguments, petv.packArguments);
if (follow(tf->type) == follow(signature.fn.type) && (signature.arguments != typeArguments || signature.packArguments != packArguments))
{
foundInfiniteType = true;
return false;
}
return true;
}
};
struct InstantiationQueuer : TypeOnceVisitor
{
ConstraintSolver* solver;
NotNull<Scope> scope;
Location location;
explicit InstantiationQueuer(NotNull<Scope> scope, const Location& location, ConstraintSolver* solver)
: solver(solver)
, scope(scope)
, location(location)
{
}
bool visit(TypeId ty, const PendingExpansionType& petv) override
{
solver->pushConstraint(scope, location, TypeAliasExpansionConstraint{ty});
return false;
}
};
bool ConstraintSolver::tryDispatch(const TypeAliasExpansionConstraint& c, NotNull<const Constraint> constraint)
{
const PendingExpansionType* petv = get<PendingExpansionType>(follow(c.target));
if (!petv)
{
unblock(c.target);
return true;
}
auto bindResult = [this, &c](TypeId result) {
asMutable(c.target)->ty.emplace<BoundType>(result);
unblock(c.target);
};
std::optional<TypeFun> tf = (petv->prefix) ? constraint->scope->lookupImportedType(petv->prefix->value, petv->name.value)
: constraint->scope->lookupType(petv->name.value);
if (!tf.has_value())
{
reportError(UnknownSymbol{petv->name.value, UnknownSymbol::Context::Type}, constraint->location);
bindResult(errorRecoveryType());
return true;
}
// If there are no parameters to the type function we can just use the type
// directly.
if (tf->typeParams.empty() && tf->typePackParams.empty())
{
bindResult(tf->type);
return true;
}
auto [typeArguments, packArguments] = saturateArguments(arena, builtinTypes, *tf, petv->typeArguments, petv->packArguments);
bool sameTypes = std::equal(typeArguments.begin(), typeArguments.end(), tf->typeParams.begin(), tf->typeParams.end(), [](auto&& itp, auto&& p) {
return itp == p.ty;
});
bool samePacks =
std::equal(packArguments.begin(), packArguments.end(), tf->typePackParams.begin(), tf->typePackParams.end(), [](auto&& itp, auto&& p) {
return itp == p.tp;
});
// If we're instantiating the type with its generic saturatedTypeArguments we are
// performing the identity substitution. We can just short-circuit and bind
// to the TypeFun's type.
if (sameTypes && samePacks)
{
bindResult(tf->type);
return true;
}
InstantiationSignature signature{
*tf,
typeArguments,
packArguments,
};
// If we use the same signature, we don't need to bother trying to
// instantiate the alias again, since the instantiation should be
// deterministic.
if (TypeId* cached = instantiatedAliases.find(signature))
{
bindResult(*cached);
return true;
}
// In order to prevent infinite types from being expanded and causing us to
// cycle infinitely, we need to scan the type function for cases where we
// expand the same alias with different type saturatedTypeArguments. See
// https://github.com/Roblox/luau/pull/68 for the RFC responsible for this.
// This is a little nicer than using a recursion limit because we can catch
// the infinite expansion before actually trying to expand it.
InfiniteTypeFinder itf{this, signature, constraint->scope};
itf.traverse(tf->type);
if (itf.foundInfiniteType)
{
// TODO (CLI-56761): Report an error.
bindResult(errorRecoveryType());
reportError(GenericError{"Recursive type being used with different parameters"}, constraint->location);
return true;
}
ApplyTypeFunction applyTypeFunction{arena};
for (size_t i = 0; i < typeArguments.size(); ++i)
{
applyTypeFunction.typeArguments[tf->typeParams[i].ty] = typeArguments[i];
}
for (size_t i = 0; i < packArguments.size(); ++i)
{
applyTypeFunction.typePackArguments[tf->typePackParams[i].tp] = packArguments[i];
}
std::optional<TypeId> maybeInstantiated = applyTypeFunction.substitute(tf->type);
// Note that ApplyTypeFunction::encounteredForwardedType is never set in
// DCR, because we do not use free types for forward-declared generic
// aliases.
if (!maybeInstantiated.has_value())
{
// TODO (CLI-56761): Report an error.
bindResult(errorRecoveryType());
return true;
}
TypeId instantiated = *maybeInstantiated;
TypeId target = follow(instantiated);
// The application is not recursive, so we need to queue up application of
// any child type function instantiations within the result in order for it
// to be complete.
InstantiationQueuer queuer{constraint->scope, constraint->location, this};
queuer.traverse(target);
if (target->persistent)
{
bindResult(target);
return true;
}
// Type function application will happily give us the exact same type if
// there are e.g. generic saturatedTypeArguments that go unused.
bool needsClone = follow(tf->type) == target;
// Only tables have the properties we're trying to set.
TableType* ttv = getMutableTableType(target);
if (ttv)
{
if (needsClone)
{
// Substitution::clone is a shallow clone. If this is a
// metatable type, we want to mutate its table, so we need to
// explicitly clone that table as well. If we don't, we will
// mutate another module's type surface and cause a
// use-after-free.
if (get<MetatableType>(target))
{
instantiated = applyTypeFunction.clone(target);
MetatableType* mtv = getMutable<MetatableType>(instantiated);
mtv->table = applyTypeFunction.clone(mtv->table);
ttv = getMutable<TableType>(mtv->table);
}
else if (get<TableType>(target))
{
instantiated = applyTypeFunction.clone(target);
ttv = getMutable<TableType>(instantiated);
}
target = follow(instantiated);
}
ttv->instantiatedTypeParams = typeArguments;
ttv->instantiatedTypePackParams = packArguments;
// TODO: Fill in definitionModuleName.
}
bindResult(target);
instantiatedAliases[signature] = target;
return true;
}
bool ConstraintSolver::tryDispatch(const FunctionCallConstraint& c, NotNull<const Constraint> constraint)
{
TypeId fn = follow(c.fn);
TypePackId argsPack = follow(c.argsPack);
TypePackId result = follow(c.result);
if (isBlocked(fn))
{
return block(c.fn, constraint);
}
auto collapse = [](const auto* t) -> std::optional<TypeId> {
auto it = begin(t);
auto endIt = end(t);
LUAU_ASSERT(it != endIt);
TypeId fst = follow(*it);
while (it != endIt)
{
if (follow(*it) != fst)
return std::nullopt;
++it;
}
return fst;
};
// Sometimes the `fn` type is a union/intersection, but whose constituents are all the same pointer.
if (auto ut = get<UnionType>(fn))
fn = collapse(ut).value_or(fn);
else if (auto it = get<IntersectionType>(fn))
fn = collapse(it).value_or(fn);
// We don't support magic __call metamethods.
if (std::optional<TypeId> callMm = findMetatableEntry(builtinTypes, errors, fn, "__call", constraint->location))
{
std::vector<TypeId> args{fn};
for (TypeId arg : c.argsPack)
args.push_back(arg);
argsPack = arena->addTypePack(TypePack{args, {}});
fn = *callMm;
asMutable(c.result)->ty.emplace<FreeTypePack>(constraint->scope);
}
else
{
const FunctionType* ftv = get<FunctionType>(fn);
bool usedMagic = false;
if (ftv)
{
if (ftv->dcrMagicFunction)
usedMagic = ftv->dcrMagicFunction(MagicFunctionCallContext{NotNull(this), c.callSite, c.argsPack, result});
if (ftv->dcrMagicRefinement)
ftv->dcrMagicRefinement(MagicRefinementContext{constraint->scope, c.callSite, c.discriminantTypes});
}
if (!usedMagic)
asMutable(c.result)->ty.emplace<FreeTypePack>(constraint->scope);
}
for (std::optional<TypeId> ty : c.discriminantTypes)
{
if (!ty || !isBlocked(*ty))
continue;
// We use `any` here because the discriminant type may be pointed at by both branches,
// where the discriminant type is not negated, and the other where it is negated, i.e.
// `unknown ~ unknown` and `~unknown ~ never`, so `T & unknown ~ T` and `T & ~unknown ~ never`
// v.s.
// `any ~ any` and `~any ~ any`, so `T & any ~ T` and `T & ~any ~ T`
//
// In practice, users cannot negate `any`, so this is an implementation detail we can always change.
*asMutable(follow(*ty)) = BoundType{builtinTypes->anyType};
}
TypeId instantiatedTy = arena->addType(BlockedType{});
TypeId inferredTy = arena->addType(FunctionType{TypeLevel{}, constraint->scope.get(), argsPack, c.result});
auto pushConstraintGreedy = [this, constraint](ConstraintV cv) -> Constraint* {
std::unique_ptr<Constraint> c = std::make_unique<Constraint>(constraint->scope, constraint->location, std::move(cv));
NotNull<Constraint> borrow{c.get()};
bool ok = tryDispatch(borrow, false);
if (ok)
return nullptr;
solverConstraints.push_back(std::move(c));
unsolvedConstraints.push_back(borrow);
return borrow;
};
// HACK: We don't want other constraints to act on the free type pack
// created above until after these two constraints are solved, so we try to
// dispatch them directly.
auto ic = pushConstraintGreedy(InstantiationConstraint{instantiatedTy, fn});
auto sc = pushConstraintGreedy(SubtypeConstraint{instantiatedTy, inferredTy});
// Anything that is blocked on this constraint must also be blocked on our
// synthesized constraints.
auto blockedIt = blocked.find(constraint.get());
if (blockedIt != blocked.end())
{
for (const auto& blockedConstraint : blockedIt->second)
{
if (ic)
block(NotNull{ic}, blockedConstraint);
if (sc)
block(NotNull{sc}, blockedConstraint);
}
}
unblock(c.result);
return true;
}
bool ConstraintSolver::tryDispatch(const PrimitiveTypeConstraint& c, NotNull<const Constraint> constraint)
{
TypeId expectedType = follow(c.expectedType);
if (isBlocked(expectedType) || get<PendingExpansionType>(expectedType))
return block(expectedType, constraint);
TypeId bindTo = maybeSingleton(expectedType) ? c.singletonType : c.multitonType;
asMutable(c.resultType)->ty.emplace<BoundType>(bindTo);
return true;
}
bool ConstraintSolver::tryDispatch(const HasPropConstraint& c, NotNull<const Constraint> constraint)
{
TypeId subjectType = follow(c.subjectType);
if (isBlocked(subjectType) || get<PendingExpansionType>(subjectType))
return block(subjectType, constraint);
if (get<FreeType>(subjectType))
{
TableType& ttv = asMutable(subjectType)->ty.emplace<TableType>(TableState::Free, TypeLevel{}, constraint->scope);
ttv.props[c.prop] = Property{c.resultType};
asMutable(c.resultType)->ty.emplace<FreeType>(constraint->scope);
unblock(c.resultType);
return true;
}
subjectType = reducer->reduce(subjectType).value_or(subjectType);
std::optional<TypeId> resultType = lookupTableProp(subjectType, c.prop);
if (!resultType)
{
asMutable(c.resultType)->ty.emplace<BoundType>(builtinTypes->errorRecoveryType());
unblock(c.resultType);
return true;
}
if (isBlocked(*resultType))
{
block(*resultType, constraint);
return false;
}
asMutable(c.resultType)->ty.emplace<BoundType>(*resultType);
return true;
}
static bool isUnsealedTable(TypeId ty)
{
ty = follow(ty);
const TableType* ttv = get<TableType>(ty);
return ttv && ttv->state == TableState::Unsealed;
}
/**
* Create a shallow copy of `ty` and its properties along `path`. Insert a new
* property (the last segment of `path`) into the tail table with the value `t`.
*
* On success, returns the new outermost table type. If the root table or any
* of its subkeys are not unsealed tables, the function fails and returns
* std::nullopt.
*
* TODO: Prove that we completely give up in the face of indexers and
* metatables.
*/
static std::optional<TypeId> updateTheTableType(NotNull<TypeArena> arena, TypeId ty, const std::vector<std::string>& path, TypeId replaceTy)
{
if (path.empty())
return std::nullopt;
// First walk the path and ensure that it's unsealed tables all the way
// to the end.
{
TypeId t = ty;
for (size_t i = 0; i < path.size() - 1; ++i)
{
if (!isUnsealedTable(t))
return std::nullopt;
const TableType* tbl = get<TableType>(t);
auto it = tbl->props.find(path[i]);
if (it == tbl->props.end())
return std::nullopt;
t = it->second.type;
}
// The last path segment should not be a property of the table at all.
// We are not changing property types. We are only admitting this one
// new property to be appended.
if (!isUnsealedTable(t))
return std::nullopt;
const TableType* tbl = get<TableType>(t);
if (0 != tbl->props.count(path.back()))
return std::nullopt;
}
const TypeId res = shallowClone(ty, arena);
TypeId t = res;
for (size_t i = 0; i < path.size() - 1; ++i)
{
const std::string segment = path[i];
TableType* ttv = getMutable<TableType>(t);
LUAU_ASSERT(ttv);
auto propIt = ttv->props.find(segment);
if (propIt != ttv->props.end())
{
LUAU_ASSERT(isUnsealedTable(propIt->second.type));
t = shallowClone(follow(propIt->second.type), arena);
ttv->props[segment].type = t;
}
else
return std::nullopt;
}
TableType* ttv = getMutable<TableType>(t);
LUAU_ASSERT(ttv);
const std::string lastSegment = path.back();
LUAU_ASSERT(0 == ttv->props.count(lastSegment));
ttv->props[lastSegment] = Property{replaceTy};
return res;
}
bool ConstraintSolver::tryDispatch(const SetPropConstraint& c, NotNull<const Constraint> constraint, bool force)
{
TypeId subjectType = follow(c.subjectType);
if (isBlocked(subjectType))
return block(subjectType, constraint);
if (!force && get<FreeType>(subjectType))
return block(subjectType, constraint);
std::optional<TypeId> existingPropType = subjectType;
for (const std::string& segment : c.path)
{
ErrorVec e;
std::optional<TypeId> propTy = lookupTableProp(*existingPropType, segment);
if (!propTy)
{
existingPropType = std::nullopt;
break;
}
else if (isBlocked(*propTy))
return block(*propTy, constraint);
else
existingPropType = follow(*propTy);
}
auto bind = [](TypeId a, TypeId b) {
asMutable(a)->ty.emplace<BoundType>(b);
};
if (existingPropType)
{
if (!isBlocked(c.propType))
unify(c.propType, *existingPropType, constraint->scope);
bind(c.resultType, c.subjectType);
return true;
}
if (get<AnyType>(subjectType) || get<ErrorType>(subjectType) || get<NeverType>(subjectType))
{
bind(c.resultType, subjectType);
return true;
}
if (get<FreeType>(subjectType))
{
TypeId ty = arena->freshType(constraint->scope);
// Mint a chain of free tables per c.path
for (auto it = rbegin(c.path); it != rend(c.path); ++it)
{
TableType t{TableState::Free, TypeLevel{}, constraint->scope};
t.props[*it] = {ty};
ty = arena->addType(std::move(t));
}
LUAU_ASSERT(ty);
bind(subjectType, ty);
if (follow(c.resultType) != follow(ty))
bind(c.resultType, ty);
return true;
}
else if (auto ttv = getMutable<TableType>(subjectType))
{
if (ttv->state == TableState::Free)
{
LUAU_ASSERT(!subjectType->persistent);
ttv->props[c.path[0]] = Property{c.propType};
bind(c.resultType, c.subjectType);
return true;
}
else if (ttv->state == TableState::Unsealed)
{
LUAU_ASSERT(!subjectType->persistent);
std::optional<TypeId> augmented = updateTheTableType(NotNull{arena}, subjectType, c.path, c.propType);
bind(c.resultType, augmented.value_or(subjectType));
bind(subjectType, c.resultType);
return true;
}
else
{
bind(c.resultType, subjectType);
return true;
}
}
else if (get<ClassType>(subjectType))
{
// Classes never change shape as a result of property assignments.
// The result is always the subject.
bind(c.resultType, subjectType);
return true;
}
LUAU_ASSERT(0);
return true;
}
bool ConstraintSolver::tryDispatch(const SetIndexerConstraint& c, NotNull<const Constraint> constraint, bool force)
{
TypeId subjectType = follow(c.subjectType);
if (isBlocked(subjectType))
return block(subjectType, constraint);
if (auto ft = get<FreeType>(subjectType))
{
Scope* scope = ft->scope;
TableType* tt = &asMutable(subjectType)->ty.emplace<TableType>(TableState::Free, TypeLevel{}, scope);
tt->indexer = TableIndexer{c.indexType, c.propType};
asMutable(c.resultType)->ty.emplace<BoundType>(subjectType);
asMutable(c.propType)->ty.emplace<FreeType>(scope);
unblock(c.propType);
unblock(c.resultType);
return true;
}
else if (auto tt = get<TableType>(subjectType))
{
if (tt->indexer)
{
// TODO This probably has to be invariant.
unify(c.indexType, tt->indexer->indexType, constraint->scope);
asMutable(c.propType)->ty.emplace<BoundType>(tt->indexer->indexResultType);
asMutable(c.resultType)->ty.emplace<BoundType>(subjectType);
unblock(c.propType);
unblock(c.resultType);
return true;
}
else if (tt->state == TableState::Free || tt->state == TableState::Unsealed)
{
auto mtt = getMutable<TableType>(subjectType);
mtt->indexer = TableIndexer{c.indexType, c.propType};
asMutable(c.propType)->ty.emplace<FreeType>(tt->scope);
asMutable(c.resultType)->ty.emplace<BoundType>(subjectType);
unblock(c.propType);
unblock(c.resultType);
return true;
}
// Do not augment sealed or generic tables that lack indexers
}
asMutable(c.propType)->ty.emplace<BoundType>(builtinTypes->errorRecoveryType());
asMutable(c.resultType)->ty.emplace<BoundType>(builtinTypes->errorRecoveryType());
unblock(c.propType);
unblock(c.resultType);
return true;
}
bool ConstraintSolver::tryDispatch(const SingletonOrTopTypeConstraint& c, NotNull<const Constraint> constraint)
{
if (isBlocked(c.discriminantType))
return false;
TypeId followed = follow(c.discriminantType);
// `nil` is a singleton type too! There's only one value of type `nil`.
if (c.negated && (get<SingletonType>(followed) || isNil(followed)))
*asMutable(c.resultType) = NegationType{c.discriminantType};
else if (!c.negated && get<SingletonType>(followed))
*asMutable(c.resultType) = BoundType{c.discriminantType};
else
*asMutable(c.resultType) = BoundType{builtinTypes->unknownType};
return true;
}
bool ConstraintSolver::tryDispatch(const UnpackConstraint& c, NotNull<const Constraint> constraint)
{
TypePackId sourcePack = follow(c.sourcePack);
TypePackId resultPack = follow(c.resultPack);
if (isBlocked(sourcePack))
return block(sourcePack, constraint);
if (isBlocked(resultPack))
{
asMutable(resultPack)->ty.emplace<BoundTypePack>(sourcePack);
unblock(resultPack);
return true;
}
TypePack srcPack = extendTypePack(*arena, builtinTypes, sourcePack, size(resultPack));
auto destIter = begin(resultPack);
auto destEnd = end(resultPack);
size_t i = 0;
while (destIter != destEnd)
{
if (i >= srcPack.head.size())
break;
TypeId srcTy = follow(srcPack.head[i]);
if (isBlocked(*destIter))
{
if (follow(srcTy) == *destIter)
{
// Cyclic type dependency. (????)
asMutable(*destIter)->ty.emplace<FreeType>(constraint->scope);
}
else
asMutable(*destIter)->ty.emplace<BoundType>(srcTy);
unblock(*destIter);
}
else
unify(*destIter, srcTy, constraint->scope);
++destIter;
++i;
}
// We know that resultPack does not have a tail, but we don't know if
// sourcePack is long enough to fill every value. Replace every remaining
// result TypeId with the error recovery type.
while (destIter != destEnd)
{
if (isBlocked(*destIter))
{
asMutable(*destIter)->ty.emplace<BoundType>(builtinTypes->errorRecoveryType());
unblock(*destIter);
}
++destIter;
}
return true;
}
bool ConstraintSolver::tryDispatchIterableTable(TypeId iteratorTy, const IterableConstraint& c, NotNull<const Constraint> constraint, bool force)
{
auto block_ = [&](auto&& t) {
if (force)
{
// TODO: I believe it is the case that, if we are asked to force
// this constraint, then we can do nothing but fail. I'd like to
// find a code sample that gets here.
LUAU_ASSERT(false);
}
else
block(t, constraint);
return false;
};
// We may have to block here if we don't know what the iteratee type is,
// if it's a free table, if we don't know it has a metatable, and so on.
iteratorTy = follow(iteratorTy);
if (get<FreeType>(iteratorTy))
return block_(iteratorTy);
auto anyify = [&](auto ty) {
Anyification anyify{arena, constraint->scope, builtinTypes, &iceReporter, builtinTypes->anyType, builtinTypes->anyTypePack};
std::optional anyified = anyify.substitute(ty);
if (!anyified)
reportError(CodeTooComplex{}, constraint->location);
else
unify(*anyified, ty, constraint->scope);
};
auto errorify = [&](auto ty) {
Anyification anyify{arena, constraint->scope, builtinTypes, &iceReporter, errorRecoveryType(), errorRecoveryTypePack()};
std::optional errorified = anyify.substitute(ty);
if (!errorified)
reportError(CodeTooComplex{}, constraint->location);
else
unify(*errorified, ty, constraint->scope);
};
if (get<AnyType>(iteratorTy))
{
anyify(c.variables);
return true;
}
if (get<ErrorType>(iteratorTy))
{
errorify(c.variables);
return true;
}
// Irksome: I don't think we have any way to guarantee that this table
// type never has a metatable.
if (auto iteratorTable = get<TableType>(iteratorTy))
{
if (iteratorTable->state == TableState::Free)
return block_(iteratorTy);
if (iteratorTable->indexer)
{
TypePackId expectedVariablePack = arena->addTypePack({iteratorTable->indexer->indexType, iteratorTable->indexer->indexResultType});
unify(c.variables, expectedVariablePack, constraint->scope);
}
else
errorify(c.variables);
}
else if (std::optional<TypeId> iterFn = findMetatableEntry(builtinTypes, errors, iteratorTy, "__iter", Location{}))
{
if (isBlocked(*iterFn))
{
return block(*iterFn, constraint);
}
Instantiation instantiation(TxnLog::empty(), arena, TypeLevel{}, constraint->scope);
if (std::optional<TypeId> instantiatedIterFn = instantiation.substitute(*iterFn))
{
if (auto iterFtv = get<FunctionType>(*instantiatedIterFn))
{
TypePackId expectedIterArgs = arena->addTypePack({iteratorTy});
unify(iterFtv->argTypes, expectedIterArgs, constraint->scope);
TypePack iterRets = extendTypePack(*arena, builtinTypes, iterFtv->retTypes, 2);
if (iterRets.head.size() < 1)
{
// We've done what we can; this will get reported as an
// error by the type checker.
return true;
}
TypeId nextFn = iterRets.head[0];
TypeId table = iterRets.head.size() == 2 ? iterRets.head[1] : arena->freshType(constraint->scope);
if (std::optional<TypeId> instantiatedNextFn = instantiation.substitute(nextFn))
{
const TypeId firstIndex = arena->freshType(constraint->scope);
// nextTy : (iteratorTy, indexTy?) -> (indexTy, valueTailTy...)
const TypePackId nextArgPack = arena->addTypePack({table, arena->addType(UnionType{{firstIndex, builtinTypes->nilType}})});
const TypePackId valueTailTy = arena->addTypePack(FreeTypePack{constraint->scope});
const TypePackId nextRetPack = arena->addTypePack(TypePack{{firstIndex}, valueTailTy});
const TypeId expectedNextTy = arena->addType(FunctionType{nextArgPack, nextRetPack});
unify(*instantiatedNextFn, expectedNextTy, constraint->scope);
pushConstraint(constraint->scope, constraint->location, PackSubtypeConstraint{c.variables, nextRetPack});
}
else
{
reportError(UnificationTooComplex{}, constraint->location);
}
}
else
{
// TODO: Support __call and function overloads (what does an overload even mean for this?)
}
}
else
{
reportError(UnificationTooComplex{}, constraint->location);
}
}
else if (auto iteratorMetatable = get<MetatableType>(iteratorTy))
{
TypeId metaTy = follow(iteratorMetatable->metatable);
if (get<FreeType>(metaTy))
return block_(metaTy);
LUAU_ASSERT(false);
}
else
errorify(c.variables);
return true;
}
bool ConstraintSolver::tryDispatchIterableFunction(
TypeId nextTy, TypeId tableTy, TypeId firstIndexTy, const IterableConstraint& c, NotNull<const Constraint> constraint, bool force)
{
// We need to know whether or not this type is nil or not.
// If we don't know, block and reschedule ourselves.
firstIndexTy = follow(firstIndexTy);
if (get<FreeType>(firstIndexTy))
{
if (force)
LUAU_ASSERT(false);
else
block(firstIndexTy, constraint);
return false;
}
const TypeId firstIndex = isNil(firstIndexTy) ? arena->freshType(constraint->scope) // FIXME: Surely this should be a union (free | nil)
: firstIndexTy;
// nextTy : (tableTy, indexTy?) -> (indexTy?, valueTailTy...)
const TypePackId nextArgPack = arena->addTypePack({tableTy, arena->addType(UnionType{{firstIndex, builtinTypes->nilType}})});
const TypePackId valueTailTy = arena->addTypePack(FreeTypePack{constraint->scope});
const TypePackId nextRetPack = arena->addTypePack(TypePack{{firstIndex}, valueTailTy});
const TypeId expectedNextTy = arena->addType(FunctionType{TypeLevel{}, constraint->scope, nextArgPack, nextRetPack});
unify(nextTy, expectedNextTy, constraint->scope);
auto it = begin(nextRetPack);
std::vector<TypeId> modifiedNextRetHead;
// The first value is never nil in the context of the loop, even if it's nil
// in the next function's return type, because the loop will not advance if
// it's nil.
if (it != end(nextRetPack))
{
TypeId firstRet = *it;
TypeId modifiedFirstRet = stripNil(builtinTypes, *arena, firstRet);
modifiedNextRetHead.push_back(modifiedFirstRet);
++it;
}
for (; it != end(nextRetPack); ++it)
modifiedNextRetHead.push_back(*it);
TypePackId modifiedNextRetPack = arena->addTypePack(std::move(modifiedNextRetHead), it.tail());
pushConstraint(constraint->scope, constraint->location, PackSubtypeConstraint{c.variables, modifiedNextRetPack});
return true;
}
std::optional<TypeId> ConstraintSolver::lookupTableProp(TypeId subjectType, const std::string& propName)
{
std::unordered_set<TypeId> seen;
return lookupTableProp(subjectType, propName, seen);
}
std::optional<TypeId> ConstraintSolver::lookupTableProp(TypeId subjectType, const std::string& propName, std::unordered_set<TypeId>& seen)
{
if (!seen.insert(subjectType).second)
return std::nullopt;
auto collectParts = [&](auto&& unionOrIntersection) -> std::pair<std::optional<TypeId>, std::vector<TypeId>> {
std::optional<TypeId> blocked;
std::vector<TypeId> parts;
std::vector<TypeId> freeParts;
for (TypeId expectedPart : unionOrIntersection)
{
expectedPart = follow(expectedPart);
if (isBlocked(expectedPart) || get<PendingExpansionType>(expectedPart))
blocked = expectedPart;
else if (const TableType* ttv = get<TableType>(follow(expectedPart)))
{
if (auto prop = ttv->props.find(propName); prop != ttv->props.end())
parts.push_back(prop->second.type);
else if (ttv->indexer && maybeString(ttv->indexer->indexType))
parts.push_back(ttv->indexer->indexResultType);
}
else if (get<FreeType>(expectedPart))
{
freeParts.push_back(expectedPart);
}
}
// If the only thing resembling a match is a single fresh type, we can
// confidently tablify it. If other types match or if there are more
// than one free type, we can't do anything.
if (parts.empty() && 1 == freeParts.size())
{
TypeId freePart = freeParts.front();
const FreeType* ft = get<FreeType>(freePart);
LUAU_ASSERT(ft);
Scope* scope = ft->scope;
TableType* tt = &asMutable(freePart)->ty.emplace<TableType>();
tt->state = TableState::Free;
tt->scope = scope;
TypeId propType = arena->freshType(scope);
tt->props[propName] = Property{propType};
parts.push_back(propType);
}
return {blocked, parts};
};
std::optional<TypeId> resultType;
if (get<AnyType>(subjectType) || get<NeverType>(subjectType))
{
return subjectType;
}
else if (auto ttv = getMutable<TableType>(subjectType))
{
if (auto prop = ttv->props.find(propName); prop != ttv->props.end())
resultType = prop->second.type;
else if (ttv->indexer && maybeString(ttv->indexer->indexType))
resultType = ttv->indexer->indexResultType;
else if (ttv->state == TableState::Free)
{
resultType = arena->addType(FreeType{ttv->scope});
ttv->props[propName] = Property{*resultType};
}
}
else if (auto mt = get<MetatableType>(subjectType))
{
if (auto p = lookupTableProp(mt->table, propName, seen))
return p;
TypeId mtt = follow(mt->metatable);
if (get<BlockedType>(mtt))
return mtt;
else if (auto metatable = get<TableType>(mtt))
{
auto indexProp = metatable->props.find("__index");
if (indexProp == metatable->props.end())
return std::nullopt;
// TODO: __index can be an overloaded function.
TypeId indexType = follow(indexProp->second.type);
if (auto ft = get<FunctionType>(indexType))
{
std::optional<TypeId> ret = first(ft->retTypes);
if (ret)
return *ret;
else
return std::nullopt;
}
return lookupTableProp(indexType, propName, seen);
}
}
else if (auto ct = get<ClassType>(subjectType))
{
while (ct)
{
if (auto prop = ct->props.find(propName); prop != ct->props.end())
return prop->second.type;
else if (ct->parent)
ct = get<ClassType>(follow(*ct->parent));
else
break;
}
}
else if (auto pt = get<PrimitiveType>(subjectType); pt && pt->metatable)
{
const TableType* metatable = get<TableType>(follow(*pt->metatable));
LUAU_ASSERT(metatable);
auto indexProp = metatable->props.find("__index");
if (indexProp == metatable->props.end())
return std::nullopt;
return lookupTableProp(indexProp->second.type, propName, seen);
}
else if (auto utv = get<UnionType>(subjectType))
{
auto [blocked, parts] = collectParts(utv);
if (blocked)
resultType = *blocked;
else if (parts.size() == 1)
resultType = parts[0];
else if (parts.size() > 1)
resultType = arena->addType(UnionType{std::move(parts)});
// otherwise, nothing: no matching property
}
else if (auto itv = get<IntersectionType>(subjectType))
{
auto [blocked, parts] = collectParts(itv);
if (blocked)
resultType = *blocked;
else if (parts.size() == 1)
resultType = parts[0];
else if (parts.size() > 1)
resultType = arena->addType(IntersectionType{std::move(parts)});
// otherwise, nothing: no matching property
}
return resultType;
}
void ConstraintSolver::block_(BlockedConstraintId target, NotNull<const Constraint> constraint)
{
blocked[target].push_back(constraint);
auto& count = blockedConstraints[constraint];
count += 1;
}
void ConstraintSolver::block(NotNull<const Constraint> target, NotNull<const Constraint> constraint)
{
if (FFlag::DebugLuauLogSolverToJson)
logger->pushBlock(constraint, target);
if (FFlag::DebugLuauLogSolver)
printf("block Constraint %s on\t%s\n", toString(*target, opts).c_str(), toString(*constraint, opts).c_str());
block_(target.get(), constraint);
}
bool ConstraintSolver::block(TypeId target, NotNull<const Constraint> constraint)
{
if (FFlag::DebugLuauLogSolverToJson)
logger->pushBlock(constraint, target);
if (FFlag::DebugLuauLogSolver)
printf("block TypeId %s on\t%s\n", toString(target, opts).c_str(), toString(*constraint, opts).c_str());
block_(follow(target), constraint);
return false;
}
bool ConstraintSolver::block(TypePackId target, NotNull<const Constraint> constraint)
{
if (FFlag::DebugLuauLogSolverToJson)
logger->pushBlock(constraint, target);
if (FFlag::DebugLuauLogSolver)
printf("block TypeId %s on\t%s\n", toString(target, opts).c_str(), toString(*constraint, opts).c_str());
block_(target, constraint);
return false;
}
struct Blocker : TypeOnceVisitor
{
NotNull<ConstraintSolver> solver;
NotNull<const Constraint> constraint;
bool blocked = false;
explicit Blocker(NotNull<ConstraintSolver> solver, NotNull<const Constraint> constraint)
: solver(solver)
, constraint(constraint)
{
}
bool visit(TypeId ty, const BlockedType&)
{
blocked = true;
solver->block(ty, constraint);
return false;
}
bool visit(TypeId ty, const PendingExpansionType&)
{
blocked = true;
solver->block(ty, constraint);
return false;
}
};
bool ConstraintSolver::recursiveBlock(TypeId target, NotNull<const Constraint> constraint)
{
Blocker blocker{NotNull{this}, constraint};
blocker.traverse(target);
return !blocker.blocked;
}
bool ConstraintSolver::recursiveBlock(TypePackId pack, NotNull<const Constraint> constraint)
{
Blocker blocker{NotNull{this}, constraint};
blocker.traverse(pack);
return !blocker.blocked;
}
void ConstraintSolver::unblock_(BlockedConstraintId progressed)
{
auto it = blocked.find(progressed);
if (it == blocked.end())
return;
// unblocked should contain a value always, because of the above check
for (NotNull<const Constraint> unblockedConstraint : it->second)
{
auto& count = blockedConstraints[unblockedConstraint];
if (FFlag::DebugLuauLogSolver)
printf("Unblocking count=%d\t%s\n", int(count), toString(*unblockedConstraint, opts).c_str());
// This assertion being hit indicates that `blocked` and
// `blockedConstraints` desynchronized at some point. This is problematic
// because we rely on this count being correct to skip over blocked
// constraints.
LUAU_ASSERT(count > 0);
count -= 1;
}
blocked.erase(it);
}
void ConstraintSolver::unblock(NotNull<const Constraint> progressed)
{
if (FFlag::DebugLuauLogSolverToJson)
logger->popBlock(progressed);
return unblock_(progressed.get());
}
void ConstraintSolver::unblock(TypeId progressed)
{
if (FFlag::DebugLuauLogSolverToJson)
logger->popBlock(progressed);
unblock_(progressed);
if (auto bt = get<BoundType>(progressed))
unblock(bt->boundTo);
}
void ConstraintSolver::unblock(TypePackId progressed)
{
if (FFlag::DebugLuauLogSolverToJson)
logger->popBlock(progressed);
return unblock_(progressed);
}
void ConstraintSolver::unblock(const std::vector<TypeId>& types)
{
for (TypeId t : types)
unblock(t);
}
void ConstraintSolver::unblock(const std::vector<TypePackId>& packs)
{
for (TypePackId t : packs)
unblock(t);
}
bool ConstraintSolver::isBlocked(TypeId ty)
{
return nullptr != get<BlockedType>(follow(ty)) || nullptr != get<PendingExpansionType>(follow(ty));
}
bool ConstraintSolver::isBlocked(TypePackId tp)
{
return nullptr != get<BlockedTypePack>(follow(tp));
}
bool ConstraintSolver::isBlocked(NotNull<const Constraint> constraint)
{
auto blockedIt = blockedConstraints.find(constraint);
return blockedIt != blockedConstraints.end() && blockedIt->second > 0;
}
void ConstraintSolver::unify(TypeId subType, TypeId superType, NotNull<Scope> scope)
{
Unifier u{normalizer, Mode::Strict, scope, Location{}, Covariant};
u.useScopes = true;
u.tryUnify(subType, superType);
if (!u.errors.empty())
{
TypeId errorType = errorRecoveryType();
u.tryUnify(subType, errorType);
u.tryUnify(superType, errorType);
}
const auto [changedTypes, changedPacks] = u.log.getChanges();
u.log.commit();
unblock(changedTypes);
unblock(changedPacks);
}
void ConstraintSolver::unify(TypePackId subPack, TypePackId superPack, NotNull<Scope> scope)
{
UnifierSharedState sharedState{&iceReporter};
Unifier u{normalizer, Mode::Strict, scope, Location{}, Covariant};
u.useScopes = true;
u.tryUnify(subPack, superPack);
const auto [changedTypes, changedPacks] = u.log.getChanges();
u.log.commit();
unblock(changedTypes);
unblock(changedPacks);
}
NotNull<Constraint> ConstraintSolver::pushConstraint(NotNull<Scope> scope, const Location& location, ConstraintV cv)
{
std::unique_ptr<Constraint> c = std::make_unique<Constraint>(scope, location, std::move(cv));
NotNull<Constraint> borrow = NotNull(c.get());
solverConstraints.push_back(std::move(c));
unsolvedConstraints.push_back(borrow);
return borrow;
}
TypeId ConstraintSolver::resolveModule(const ModuleInfo& info, const Location& location)
{
if (info.name.empty())
{
reportError(UnknownRequire{}, location);
return errorRecoveryType();
}
std::string humanReadableName = moduleResolver->getHumanReadableModuleName(info.name);
for (const auto& [location, path] : requireCycles)
{
if (!path.empty() && path.front() == humanReadableName)
return builtinTypes->anyType;
}
ModulePtr module = moduleResolver->getModule(info.name);
if (!module)
{
if (!moduleResolver->moduleExists(info.name) && !info.optional)
reportError(UnknownRequire{humanReadableName}, location);
return errorRecoveryType();
}
if (module->type != SourceCode::Type::Module)
{
reportError(IllegalRequire{humanReadableName, "Module is not a ModuleScript. It cannot be required."}, location);
return errorRecoveryType();
}
TypePackId modulePack = module->returnType;
if (get<Unifiable::Error>(modulePack))
return errorRecoveryType();
std::optional<TypeId> moduleType = first(modulePack);
if (!moduleType)
{
reportError(IllegalRequire{humanReadableName, "Module does not return exactly 1 value. It cannot be required."}, location);
return errorRecoveryType();
}
return *moduleType;
}
void ConstraintSolver::reportError(TypeErrorData&& data, const Location& location)
{
errors.emplace_back(location, std::move(data));
errors.back().moduleName = currentModuleName;
}
void ConstraintSolver::reportError(TypeError e)
{
errors.emplace_back(std::move(e));
errors.back().moduleName = currentModuleName;
}
TypeId ConstraintSolver::errorRecoveryType() const
{
return builtinTypes->errorRecoveryType();
}
TypePackId ConstraintSolver::errorRecoveryTypePack() const
{
return builtinTypes->errorRecoveryTypePack();
}
TypeId ConstraintSolver::unionOfTypes(TypeId a, TypeId b, NotNull<Scope> scope, bool unifyFreeTypes)
{
a = follow(a);
b = follow(b);
if (unifyFreeTypes && (get<FreeType>(a) || get<FreeType>(b)))
{
Unifier u{normalizer, Mode::Strict, scope, Location{}, Covariant};
u.useScopes = true;
u.tryUnify(b, a);
if (u.errors.empty())
{
u.log.commit();
return a;
}
else
{
return builtinTypes->errorRecoveryType(builtinTypes->anyType);
}
}
if (*a == *b)
return a;
std::vector<TypeId> types = reduceUnion({a, b});
if (types.empty())
return builtinTypes->neverType;
if (types.size() == 1)
return types[0];
return arena->addType(UnionType{types});
}
} // namespace Luau
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