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TypeInferenceWalker.kt
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TypeInferenceWalker.kt
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/*
* Use of this source code is governed by the MIT license that can be
* found in the LICENSE file.
*/
package org.rust.lang.core.types.infer
import com.intellij.openapi.progress.ProgressManager
import com.intellij.psi.PsiElement
import com.intellij.util.containers.isNullOrEmpty
import org.rust.lang.core.macros.MacroExpansion
import org.rust.lang.core.macros.expandedFromSequence
import org.rust.lang.core.psi.*
import org.rust.lang.core.psi.ext.*
import org.rust.lang.core.resolve.*
import org.rust.lang.core.resolve.ref.*
import org.rust.lang.core.stubs.RsStubLiteralKind
import org.rust.lang.core.types.*
import org.rust.lang.core.types.ty.*
import org.rust.lang.utils.RsDiagnostic
import org.rust.lang.utils.evaluation.ExprValue
import org.rust.lang.utils.evaluation.RsConstExprEvaluator
import org.rust.openapiext.forEachChild
import org.rust.stdext.notEmptyOrLet
import org.rust.stdext.singleOrFilter
import org.rust.stdext.singleOrLet
class RsTypeInferenceWalker(
private val ctx: RsInferenceContext,
private val returnTy: Ty
) {
private var tryTy: Ty? = returnTy
private var yieldTy: Ty? = null
private val lookup get() = ctx.lookup
private val items get() = ctx.items
private val fulfill get() = ctx.fulfill
private val RsStructLiteralField.type: Ty get() = resolveToDeclaration()?.typeReference?.type ?: TyUnknown
private fun resolveTypeVarsWithObligations(ty: Ty): Ty {
if (!ty.hasTyInfer) return ty
val tyRes = ctx.resolveTypeVarsIfPossible(ty)
if (!tyRes.hasTyInfer) return tyRes
selectObligationsWherePossible()
return ctx.resolveTypeVarsIfPossible(tyRes)
}
private fun selectObligationsWherePossible() {
fulfill.selectWherePossible()
}
private fun inferBlockExprType(blockExpr: RsBlockExpr, expected: Ty? = null): Ty =
when {
blockExpr.isTry -> inferTryBlockExprType(blockExpr, expected)
blockExpr.isAsync -> inferAsyncBlockExprType(blockExpr)
else -> {
val type = blockExpr.block.inferType(expected)
inferLabeledExprType(blockExpr, type, true)
}
}
private fun inferTryBlockExprType(blockExpr: RsBlockExpr, expected: Ty? = null): Ty {
require(blockExpr.isTry)
val oldTryTy = tryTy
try {
tryTy = expected ?: TyInfer.TyVar()
val resultTy = tryTy ?: TyUnknown
val okTy = blockExpr.block.inferType()
registerTryProjection(resultTy, "Ok", okTy)
return resultTy
} finally {
tryTy = oldTryTy
}
}
private fun inferAsyncBlockExprType(blockExpr: RsBlockExpr): Ty {
require(blockExpr.isAsync)
val outputTy = blockExpr.block.inferType()
return items.makeFuture(outputTy)
}
fun inferFnBody(block: RsBlock): Ty =
block.inferTypeCoercableTo(returnTy)
fun inferLambdaBody(expr: RsExpr): Ty =
if (expr is RsBlockExpr) {
// skipping diverging procession for lambda body
ctx.writeExprTy(expr, returnTy)
inferFnBody(expr.block)
} else {
expr.inferTypeCoercableTo(returnTy)
}
private fun RsBlock.inferTypeCoercableTo(expected: Ty): Ty =
inferType(expected, true)
private fun RsBlock.inferType(expected: Ty? = null, coerce: Boolean = false): Ty {
var isDiverging = false
val expandedStmts = expandedStmts
val tailExpr = expandedStmts.lastOrNull()
?.let { it as? RsExpr }
?.takeIf { e ->
// If tail expr is expanded from a macro, we should check that this macro doesn't have
// semicolon (`foo!();`), otherwice it's not a tail expr but a regular statement
e.expandedFromSequence.all {
val bracesKind = it.bracesKind ?: return@all false
!bracesKind.needsSemicolon || it.semicolon == null
}
}
for (stmt in expandedStmts) {
val result = when (stmt) {
tailExpr -> false
is RsStmt -> processStatement(stmt)
is RsExpr -> stmt.inferType() == TyNever
else -> false
}
isDiverging = result || isDiverging
}
val type = (if (coerce) tailExpr?.inferTypeCoercableTo(expected!!) else tailExpr?.inferType(expected)) ?: TyUnit
return if (isDiverging) TyNever else type
}
// returns true if expr is always diverging
private fun processStatement(psi: RsStmt): Boolean = when (psi) {
is RsLetDecl -> {
val explicitTy = psi.typeReference?.type
?.let { normalizeAssociatedTypesIn(it) }
val expr = psi.expr
// We need to know type before coercion to correctly identify if expr is always diverging
// so we can't call `inferTypeCoercableTo` directly here
val (inferredTy, coercedInferredTy) = if (expr != null) {
val inferredTy = expr.inferType(explicitTy)
val coercedTy = if (explicitTy != null && coerce(expr, inferredTy, explicitTy)) {
explicitTy
} else {
inferredTy
}
inferredTy to coercedTy
} else {
TyUnknown to TyInfer.TyVar()
}
psi.pat?.extractBindings(explicitTy ?: resolveTypeVarsWithObligations(coercedInferredTy))
inferredTy == TyNever
}
is RsExprStmt -> psi.expr.inferType() == TyNever
else -> false
}
private fun RsExpr.inferType(expected: Ty? = null): Ty {
ProgressManager.checkCanceled()
if (ctx.isTypeInferred(this)) error("Trying to infer expression type twice")
if (expected != null) {
when (this) {
is RsPathExpr -> ctx.writeExpectedPathExprTy(this, expected)
is RsDotExpr -> ctx.writeExpectedDotExprTy(this, expected)
}
}
val ty = when (this) {
is RsPathExpr -> inferPathExprType(this)
is RsStructLiteral -> inferStructLiteralType(this, expected)
is RsTupleExpr -> inferRsTupleExprType(this, expected)
is RsParenExpr -> this.expr.inferType(expected)
is RsUnitExpr -> TyUnit
is RsCastExpr -> inferCastExprType(this)
is RsCallExpr -> inferCallExprType(this, expected)
is RsDotExpr -> inferDotExprType(this, expected)
is RsLitExpr -> inferLitExprType(this, expected)
is RsBlockExpr -> inferBlockExprType(this, expected)
is RsIfExpr -> inferIfExprType(this, expected)
is RsLoopExpr -> inferLoopExprType(this)
is RsWhileExpr -> inferWhileExprType(this)
is RsForExpr -> inferForExprType(this)
is RsMatchExpr -> inferMatchExprType(this, expected)
is RsUnaryExpr -> inferUnaryExprType(this, expected)
is RsBinaryExpr -> inferBinaryExprType(this)
is RsTryExpr -> inferTryExprType(this)
is RsArrayExpr -> inferArrayType(this, expected)
is RsRangeExpr -> inferRangeType(this)
is RsIndexExpr -> inferIndexExprType(this)
is RsMacroExpr -> inferMacroExprType(this, expected)
is RsLambdaExpr -> inferLambdaExprType(this, expected)
is RsYieldExpr -> inferYieldExprType(this)
is RsRetExpr -> inferRetExprType(this)
is RsBreakExpr -> inferBreakExprType(this)
is RsContExpr -> TyNever
else -> TyUnknown
}
ctx.writeExprTy(this, ty)
return ty
}
private fun RsExpr.inferTypeCoercableTo(expected: Ty): Ty {
val inferred = inferType(expected)
return if (coerce(this, inferred, expected)) expected else inferred
}
@JvmName("inferTypeCoercableTo_")
fun inferTypeCoercableTo(expr: RsExpr, expected: Ty): Ty =
expr.inferTypeCoercableTo(expected)
private fun coerce(element: RsElement, inferred: Ty, expected: Ty): Boolean {
return coerceResolved(element, resolveTypeVarsWithObligations(inferred), resolveTypeVarsWithObligations(expected))
}
private fun coerceResolved(element: RsElement, inferred: Ty, expected: Ty): Boolean {
val ok = tryCoerce(inferred, expected)
if (!ok) {
// ignoring possible false-positives (it's only basic experimental type checking)
val ignoredTys = listOf(
TyUnknown::class.java,
TyInfer.TyVar::class.java,
TyTypeParameter::class.java,
TyProjection::class.java,
TyTraitObject::class.java,
TyAnon::class.java
)
if (!expected.containsTyOfClass(ignoredTys) && !inferred.containsTyOfClass(ignoredTys)) {
// another awful hack: check that inner expressions did not annotated as an error
// to disallow annotation intersections. This should be done in a different way
if (ctx.diagnostics.all { !element.isAncestorOf(it.element) }) {
ctx.reportTypeMismatch(element, expected, inferred)
}
}
}
return ok
}
private fun tryCoerce(inferred: Ty, expected: Ty): Boolean {
return when {
inferred == TyNever -> true
// Coerce array to slice
inferred is TyReference && inferred.referenced is TyArray &&
expected is TyReference && expected.referenced is TySlice -> {
ctx.combineTypes(inferred.referenced.base, expected.referenced.elementType)
}
// Coerce reference to pointer
inferred is TyReference && expected is TyPointer &&
coerceMutability(inferred.mutability, expected.mutability) -> {
ctx.combineTypes(inferred.referenced, expected.referenced)
}
// Coerce mutable pointer to const pointer
inferred is TyPointer && inferred.mutability.isMut
&& expected is TyPointer && !expected.mutability.isMut -> {
ctx.combineTypes(inferred.referenced, expected.referenced)
}
// Coerce references
inferred is TyReference && expected is TyReference &&
coerceMutability(inferred.mutability, expected.mutability) -> {
coerceReference(inferred, expected)
}
// TODO trait object unsizing
else -> ctx.combineTypes(inferred, expected)
}
}
private fun coerceMutability(from: Mutability, to: Mutability): Boolean =
from == to || from.isMut && !to.isMut
/**
* Reborrows `&mut A` to `&mut B` and `&(mut) A` to `&B`.
* To match `A` with `B`, autoderef will be performed
*/
private fun coerceReference(inferred: TyReference, expected: TyReference): Boolean {
for (derefTy in lookup.coercionSequence(inferred).drop(1)) {
// TODO proper handling of lifetimes
val derefTyRef = TyReference(derefTy, expected.mutability, expected.region)
if (ctx.combineTypesIfOk(derefTyRef, expected)) return true
}
return false
}
private fun inferLitExprType(expr: RsLitExpr, expected: Ty?): Ty {
return when (val stubKind = expr.stubKind) {
is RsStubLiteralKind.Boolean -> TyBool
is RsStubLiteralKind.Char -> if (stubKind.isByte) TyInteger.U8 else TyChar
is RsStubLiteralKind.String -> {
// TODO infer the actual lifetime
if (stubKind.isByte) {
TyReference(TyArray(TyInteger.U8, stubKind.value?.length?.toLong() ?: 0), Mutability.IMMUTABLE)
} else {
TyReference(TyStr, Mutability.IMMUTABLE)
}
}
is RsStubLiteralKind.Integer -> {
val ty = stubKind.ty
ty ?: when (expected) {
is TyInteger -> expected
TyChar -> TyInteger.U8
is TyPointer, is TyFunction -> TyInteger.USize
else -> TyInfer.IntVar()
}
}
is RsStubLiteralKind.Float -> {
val ty = stubKind.ty
ty ?: (expected?.takeIf { it is TyFloat } ?: TyInfer.FloatVar())
}
null -> TyUnknown
}
}
private fun inferPathExprType(expr: RsPathExpr): Ty {
val path = expr.path
val resolveVariants = resolvePathRaw(path, lookup)
val assocVariants = resolveVariants.filterIsInstance<AssocItemScopeEntry>()
val filteredVariants = if (resolveVariants.size == assocVariants.size) {
val variants = filterAssocItems(assocVariants, expr)
val fnVariants = variants.mapNotNull { it.element as? RsFunction }
if (variants.size > 1 && fnVariants.size == variants.size && path.path != null) {
val resolved = collapseToTrait(fnVariants)
if (resolved != null) {
ctx.writePath(expr, variants.map { ResolvedPath.from(it) })
val subst = collapseSubst(
resolved,
variants.mapNotNull { e ->
(e.element as? RsGenericDeclaration)?.let { BoundElement(it, e.subst) }
}
)
val scopeEntry = variants.first().copy(
element = resolved,
subst = subst,
source = TraitImplSource.Collapsed((resolved.owner as RsAbstractableOwner.Trait).trait)
)
return instantiatePath(resolved, scopeEntry, expr)
}
}
variants
} else {
resolveVariants
}
ctx.writePath(expr, filteredVariants.mapNotNull { ResolvedPath.from(it) })
val first = filteredVariants.singleOrNull() ?: return TyUnknown
return instantiatePath(first.element ?: return TyUnknown, first, expr)
}
/** This works for `String::from` where multiple impls of `From` trait found for `String` */
private fun collapseToTrait(elements: List<RsFunction>): RsFunction? {
if (elements.size <= 1) return null
val traits = elements.mapNotNull {
when (val owner = it.owner) {
is RsAbstractableOwner.Impl -> owner.impl.traitRef?.resolveToTrait()
is RsAbstractableOwner.Trait -> owner.trait
else -> null
}
}
if (traits.size == elements.size && traits.toSet().size == 1) {
val fnName = elements.first().name
val trait = traits.first()
val functionList = trait.members?.functionList ?: return null
return functionList.singleOrNull { it.name == fnName }
}
return null
}
/** See test `test type arguments remap on collapse to trait` */
private fun collapseSubst(parentFn: RsFunction, variants: List<BoundElement<RsGenericDeclaration>>): Substitution {
//TODO remap lifetimes
val collapsed = mutableMapOf<TyTypeParameter, Ty>()
val generics = parentFn.generics
for (fn in variants) {
for ((key, newValue) in generics.zip(fn.positionalTypeArguments)) {
@Suppress("NAME_SHADOWING")
collapsed.compute(key) { key, oldValue ->
if (oldValue == null || oldValue == newValue) newValue else TyInfer.TyVar(key)
}
}
}
variants.first().subst[TyTypeParameter.self()]?.let { collapsed[TyTypeParameter.self()] = it }
return collapsed.toTypeSubst()
}
private fun instantiatePath(
element: RsElement,
scopeEntry: ScopeEntry,
pathExpr: RsPathExpr
): Ty {
val subst = instantiatePathGenerics(pathExpr.path, BoundElement(element, scopeEntry.subst)).subst
val type = when (element) {
is RsPatBinding -> ctx.getBindingType(element)
is RsTypeDeclarationElement -> element.declaredType
is RsEnumVariant -> element.parentEnum.declaredType
is RsFunction -> element.type
is RsConstant -> element.typeReference?.type ?: TyUnknown
is RsConstParameter -> element.typeReference?.type ?: TyUnknown
is RsSelfParameter -> element.typeOfValue
else -> return TyUnknown
}
val typeParameters = when {
scopeEntry is AssocItemScopeEntry && element is RsAbstractable -> {
val owner = element.owner
val (typeParameters, selfTy) = when (owner) {
is RsAbstractableOwner.Impl -> {
val typeParameters = ctx.instantiateBounds(owner.impl)
val selfTy = owner.impl.typeReference?.type?.substitute(typeParameters) ?: TyUnknown
subst[TyTypeParameter.self()]?.let { ctx.combineTypes(selfTy, it) }
typeParameters to selfTy
}
is RsAbstractableOwner.Trait -> {
val typeParameters = ctx.instantiateBounds(owner.trait)
// UFCS - add predicate `Self : Trait<Args>`
val selfTy = subst[TyTypeParameter.self()] ?: ctx.typeVarForParam(TyTypeParameter.self())
val newSubst = owner.trait.generics.associateBy { it }.toTypeSubst()
val boundTrait = BoundElement(owner.trait, newSubst)
.substitute(typeParameters)
val traitRef = TraitRef(selfTy, boundTrait)
fulfill.registerPredicateObligation(Obligation(Predicate.Trait(traitRef)))
when (scopeEntry.source) {
is TraitImplSource.Object, is TraitImplSource.Collapsed -> {
ctx.registerPathRefinement(pathExpr, traitRef)
}
}
typeParameters to selfTy
}
else -> emptySubstitution to null
}
if (element is RsGenericDeclaration) {
ctx.instantiateBounds(element, selfTy, typeParameters)
} else {
typeParameters
}
}
element is RsEnumVariant -> ctx.instantiateBounds(element.parentEnum)
element is RsGenericDeclaration -> ctx.instantiateBounds(element)
else -> emptySubstitution
}
unifySubst(subst, typeParameters)
val tupleFields = (element as? RsFieldsOwner)?.tupleFields
return if (tupleFields != null) {
// Treat tuple constructor as a function
TyFunction(tupleFields.tupleFieldDeclList.map { it.typeReference.type }, type)
} else {
type
}.substitute(typeParameters).foldWith(associatedTypeNormalizer)
}
private fun <T : TypeFoldable<T>> normalizeAssociatedTypesIn(ty: T): T {
val (normTy, obligations) = ctx.normalizeAssociatedTypesIn(ty)
obligations.forEach(fulfill::registerPredicateObligation)
return normTy
}
private inner class AssociatedTypeNormalizer : TypeFolder {
override fun foldTy(ty: Ty): Ty = normalizeAssociatedTypesIn(ty)
}
private val associatedTypeNormalizer = AssociatedTypeNormalizer()
private fun unifySubst(subst1: Substitution, subst2: Substitution) {
subst1.typeSubst.forEach { (k, v1) ->
subst2[k]?.let { v2 ->
if (k != v1 && k != TyTypeParameter.self() && v1 !is TyTypeParameter && v1 !is TyUnknown) {
ctx.combineTypes(v2, v1)
}
}
}
// TODO take into account the lifetimes
}
private fun inferStructLiteralType(expr: RsStructLiteral, expected: Ty?): Ty {
val boundElement = expr.path.reference.advancedDeepResolve()
if (boundElement == null) {
for (field in expr.structLiteralBody.structLiteralFieldList) {
field.expr?.inferType()
}
// Handle struct update syntax { ..expression }
expr.structLiteralBody.expr?.inferType()
return TyUnknown
}
val (element, subst) = boundElement
val genericDecl: RsGenericDeclaration? = when (element) {
is RsStructItem -> element
is RsEnumVariant -> element.parentEnum
else -> null
}
val typeParameters = genericDecl?.let { ctx.instantiateBounds(it) } ?: emptySubstitution
unifySubst(subst, typeParameters)
if (expected != null) unifySubst(typeParameters, expected.typeParameterValues)
val type = when (element) {
is RsStructItem -> element.declaredType
is RsEnumVariant -> element.parentEnum.declaredType
else -> TyUnknown
}.substitute(typeParameters)
inferStructTypeArguments(expr, typeParameters)
// Handle struct update syntax { ..expression }
expr.structLiteralBody.expr?.inferTypeCoercableTo(type)
return type
}
private fun inferStructTypeArguments(literal: RsStructLiteral, typeParameters: Substitution) {
literal.structLiteralBody.structLiteralFieldList.filterNotNull().forEach { field ->
val fieldTy = field.type.substitute(typeParameters)
val expr = field.expr
if (expr != null) {
expr.inferTypeCoercableTo(fieldTy)
} else {
val bindingTy = field.resolveToBinding()?.let { ctx.getBindingType(it) } ?: TyUnknown
coerce(field, bindingTy, fieldTy)
}
}
}
private fun inferRsTupleExprType(expr: RsTupleExpr, expected: Ty?): Ty {
return TyTuple(inferExprList(expr.exprList, (expected as? TyTuple)?.types))
}
private fun inferExprList(exprs: List<RsExpr>, expected: List<Ty>?): List<Ty> {
val extended = expected.orEmpty().asSequence().infiniteWithTyUnknown()
return exprs.asSequence().zip(extended).map { (expr, ty) -> expr.inferTypeCoercableTo(ty) }.toList()
}
private fun inferCastExprType(expr: RsCastExpr): Ty {
expr.expr.inferType()
return expr.typeReference.type
}
private fun inferCallExprType(expr: RsCallExpr, expected: Ty?): Ty {
val callee = expr.expr
val ty = resolveTypeVarsWithObligations(callee.inferType()) // or error
// `struct S; S();`
if (callee is RsPathExpr) {
ctx.getResolvedPath(callee).singleOrNull()?.element?.let {
if (it is RsFieldsOwner && it.isFieldless) {
return ty
}
}
}
val argExprs = expr.valueArgumentList.exprList
val calleeType = lookup.asTyFunction(ty)?.register() ?: unknownTyFunction(argExprs.size)
if (expected != null) ctx.combineTypes(expected, calleeType.retType)
inferArgumentTypes(calleeType.paramTypes, argExprs)
return calleeType.retType
}
private fun inferMethodCallExprType(receiver: Ty, methodCall: RsMethodCall, expected: Ty?): Ty {
val argExprs = methodCall.valueArgumentList.exprList
val callee = run {
val variants = resolveMethodCallReferenceWithReceiverType(lookup, receiver, methodCall)
val callee = pickSingleMethod(receiver, variants, methodCall)
// If we failed to resolve ambiguity just write the all possible methods
val variantsForDisplay = (callee?.let(::listOf) ?: variants)
ctx.writeResolvedMethod(methodCall, variantsForDisplay)
callee ?: variants.firstOrNull()
}
if (callee == null) {
val methodType = unknownTyFunction(argExprs.size)
inferArgumentTypes(methodType.paramTypes, argExprs)
return methodType.retType
}
var typeParameters = ctx.instantiateMethodOwnerSubstitution(callee, methodCall)
// TODO: borrow adjustments for self parameter
/*
if (callee.selfTy is TyReference) {
val adjustment = BorrowReference( callee.selfTy)
ctx.addAdjustment(methodCall.receiver, adjustment)
}
*/
typeParameters = ctx.instantiateBounds(callee.element, callee.selfTy, typeParameters)
val fnSubst = run {
val typeArguments = methodCall.typeArgumentList?.typeReferenceList.orEmpty().map { it.type }
if (typeArguments.isEmpty()) {
emptySubstitution
} else {
val parameters = callee.element.typeParameterList?.typeParameterList.orEmpty()
.map { TyTypeParameter.named(it) }
parameters.zip(typeArguments).toMap().toTypeSubst()
}
}
unifySubst(fnSubst, typeParameters)
val methodType = (callee.element.type)
.substitute(typeParameters)
.foldWith(associatedTypeNormalizer) as TyFunction
if (expected != null && !callee.element.isAsync) ctx.combineTypes(expected, methodType.retType)
// drop first element of paramTypes because it's `self` param
// and it doesn't have value in `methodCall.valueArgumentList.exprList`
inferArgumentTypes(methodType.paramTypes.drop(1), argExprs)
return methodType.retType
}
private fun <T : AssocItemScopeEntryBase<E>, E> filterAssocItems(variants: List<T>, context: RsElement): List<T> {
return variants.singleOrLet { list ->
// 1. filter traits that are not imported
TypeInferenceMarks.methodPickTraitScope.hit()
val traitToCallee = hashMapOf<RsTraitItem, MutableList<T>>()
val filtered = mutableListOf<T>()
for (callee in list) {
val trait = callee.source.impl?.traitRef?.resolveToTrait()
if (trait != null) {
traitToCallee.getOrPut(trait) { mutableListOf() }.add(callee)
} else {
filtered.add(callee) // inherent impl
}
}
traitToCallee.keys.filterInScope(context).forEach {
filtered += traitToCallee.getValue(it)
}
if (filtered.isNotEmpty()) {
filtered
} else {
TypeInferenceMarks.methodPickTraitsOutOfScope.hit()
list
}
}.singleOrFilter { callee ->
// 2. Filter methods by trait bounds (try to select all obligations for each impl)
TypeInferenceMarks.methodPickCheckBounds.hit()
val impl = callee.source.impl ?: return@singleOrFilter true
ctx.canEvaluateBounds(impl, callee.selfTy)
}
}
private fun pickSingleMethod(receiver: Ty, variants: List<MethodResolveVariant>, methodCall: RsMethodCall): MethodResolveVariant? {
val filtered = filterAssocItems(variants, methodCall).singleOrLet { list ->
// 3. Pick results matching receiver type
TypeInferenceMarks.methodPickDerefOrder.hit()
fun pick(ty: Ty): List<MethodResolveVariant> =
list.filter { it.element.selfParameter?.typeOfValue(it.selfTy) == ty }
// https://github.com/rust-lang/rust/blob/a646c912/src/librustc_typeck/check/method/probe.rs#L885
lookup.coercionSequence(receiver).mapNotNull { ty ->
pick(ty)
// TODO do something with lifetimes
.notEmptyOrLet { pick(TyReference(ty, Mutability.IMMUTABLE)) }
.notEmptyOrLet { pick(TyReference(ty, Mutability.MUTABLE)) }
.takeIf { it.isNotEmpty() }
}.firstOrNull() ?: emptyList()
}
return when (filtered.size) {
0 -> null
1 -> filtered.single()
else -> {
// 4. Try to collapse multiple resolved methods of the same trait, e.g.
// ```rust
// trait Foo<T> { fn foo(&self, _: T) {} }
// impl Foo<Bar> for S { fn foo(&self, _: Bar) {} }
// impl Foo<Baz> for S { fn foo(&self, _: Baz) {} }
// ```
// In this case we `filtered` list contains 2 function defined in 2 impls.
// We want to collapse them to the single function defined in the trait.
// Specific impl will be selected later according to the method parameter type.
val first = filtered.first()
collapseToTrait(filtered.map { it.element })?.let { fn ->
TypeInferenceMarks.methodPickCollapseTraits.hit()
MethodResolveVariant(
first.name,
fn,
first.selfTy,
first.derefCount,
TraitImplSource.Collapsed((fn.owner as RsAbstractableOwner.Trait).trait)
)
}
}
}
}
private fun unknownTyFunction(arity: Int): TyFunction =
TyFunction(generateSequence { TyUnknown }.take(arity).toList(), TyUnknown)
private fun inferArgumentTypes(argDefs: List<Ty>, argExprs: List<RsExpr>) {
// We do this just like rustc, and comments copied from rustc too
// We do this in a pretty awful way: first we typecheck any arguments
// that are not closures, then we typecheck the closures. This is so
// that we have more information about the types of arguments when we
// typecheck the functions.
for (checkLambdas in booleanArrayOf(false, true)) {
// More awful hacks: before we check argument types, try to do
// an "opportunistic" vtable resolution of any trait bounds on
// the call. This helps coercions.
if (checkLambdas) {
selectObligationsWherePossible()
}
val argDefsExt = argDefs.asSequence()
.map(ctx::resolveTypeVarsIfPossible)
// extending argument definitions to be sure that type inference launched for each arg expr
.infiniteWithTyUnknown()
for ((type, expr) in argDefsExt.zip(argExprs.asSequence().map(::unwrapParenExprs))) {
val isLambda = expr is RsLambdaExpr
if (isLambda != checkLambdas) continue
expr.inferTypeCoercableTo(type)
}
}
}
private fun inferFieldExprType(receiver: Ty, fieldLookup: RsFieldLookup): Ty {
if (fieldLookup.identifier?.text == "await" && fieldLookup.isEdition2018) {
return receiver.lookupFutureOutputTy(lookup)
}
val variants = resolveFieldLookupReferenceWithReceiverType(lookup, receiver, fieldLookup)
ctx.writeResolvedField(fieldLookup, variants.map { it.element })
val field = variants.firstOrNull()
if (field == null) {
for ((index, type) in lookup.coercionSequence(receiver).withIndex()) {
if (type is TyTuple) {
ctx.addAdjustment(fieldLookup.parentDotExpr.expr, Adjustment.Deref(receiver), index)
val fieldIndex = fieldLookup.integerLiteral?.text?.toIntOrNull() ?: return TyUnknown
return type.types.getOrElse(fieldIndex) { TyUnknown }
}
}
return TyUnknown
}
ctx.addAdjustment(fieldLookup.parentDotExpr.expr, Adjustment.Deref(receiver), field.derefCount)
val fieldElement = field.element
val raw = (fieldElement as? RsFieldDecl)?.typeReference?.type ?: TyUnknown
return raw.substitute(field.selfTy.typeParameterValues).foldWith(associatedTypeNormalizer)
}
private fun inferDotExprType(expr: RsDotExpr, expected: Ty?): Ty {
val receiver = resolveTypeVarsWithObligations(expr.expr.inferType())
val methodCall = expr.methodCall
val fieldLookup = expr.fieldLookup
return when {
methodCall != null -> inferMethodCallExprType(receiver, methodCall, expected)
fieldLookup != null -> inferFieldExprType(receiver, fieldLookup)
else -> TyUnknown
}
}
private fun inferLoopExprType(expr: RsLoopExpr): Ty {
expr.block?.inferType()
return inferLabeledExprType(expr, TyNever, false)
}
private fun inferLabeledExprType(expr: RsLabeledExpression, baseType: Ty, matchOnlyByLabel: Boolean): Ty {
val returningTypes = mutableListOf(baseType)
val label = expr.labelDecl?.name
fun collectReturningTypes(element: PsiElement, matchOnlyByLabel: Boolean) {
element.forEachChild { child ->
when (child) {
is RsBreakExpr -> {
collectReturningTypes(child, matchOnlyByLabel)
if (!matchOnlyByLabel && child.label == null || child.label?.referenceName == label) {
returningTypes += child.expr?.let(ctx::getExprType) ?: TyUnit
}
}
is RsLabeledExpression -> {
if (label != null) {
collectReturningTypes(child, true)
}
}
else -> collectReturningTypes(child, matchOnlyByLabel)
}
}
}
if (label != null || !matchOnlyByLabel) {
collectReturningTypes(expr, matchOnlyByLabel)
}
return getMoreCompleteType(returningTypes)
}
private fun inferForExprType(expr: RsForExpr): Ty {
val exprTy = resolveTypeVarsWithObligations(expr.expr?.inferType() ?: TyUnknown)
val itemTy = resolveTypeVarsWithObligations(lookup.findIteratorItemType(exprTy)?.register() ?: TyUnknown)
expr.pat?.extractBindings(itemTy)
expr.block?.inferType()
return TyUnit
}
private fun inferWhileExprType(expr: RsWhileExpr): Ty {
expr.condition?.inferTypes()
expr.block?.inferType()
return TyUnit
}
private fun inferMatchExprType(expr: RsMatchExpr, expected: Ty?): Ty {
val matchingExprTy = resolveTypeVarsWithObligations(expr.expr?.inferType() ?: TyUnknown)
val arms = expr.arms
for (arm in arms) {
arm.orPats.extractBindings(matchingExprTy)
arm.expr?.inferType(expected)
arm.matchArmGuard?.expr?.inferType(TyBool)
}
return getMoreCompleteType(arms.mapNotNull { it.expr?.let(ctx::getExprType) })
}
private fun inferUnaryExprType(expr: RsUnaryExpr, expected: Ty?): Ty {
val innerExpr = expr.expr ?: return TyUnknown
return when (expr.operatorType) {
UnaryOperator.REF -> inferRefType(innerExpr, expected, Mutability.IMMUTABLE)
UnaryOperator.REF_MUT -> inferRefType(innerExpr, expected, Mutability.MUTABLE)
UnaryOperator.DEREF -> {
// expectation must NOT be used for deref
val base = resolveTypeVarsWithObligations(innerExpr.inferType())
val deref = lookup.deref(base)
if (deref == null && base != TyUnknown) {
ctx.addDiagnostic(RsDiagnostic.DerefError(expr, base))
}
deref ?: TyUnknown
}
UnaryOperator.MINUS -> innerExpr.inferType(expected)
UnaryOperator.NOT -> innerExpr.inferType(expected)
UnaryOperator.BOX -> {
val expectedInner = (expected as? TyAdt)?.takeIf { it.item == items.Box }?.typeArguments?.getOrNull(0)
items.makeBox(innerExpr.inferType(expectedInner))
}
}
}
private fun inferRefType(expr: RsExpr, expected: Ty?, mutable: Mutability): Ty =
TyReference(expr.inferType((expected as? TyReference)?.referenced), mutable) // TODO infer the actual lifetime
private fun inferIfExprType(expr: RsIfExpr, expected: Ty?): Ty {
expr.condition?.inferTypes()
val blockTys = mutableListOf<Ty?>()
blockTys.add(expr.block?.inferType(expected))
val elseBranch = expr.elseBranch
if (elseBranch != null) {
blockTys.add(elseBranch.ifExpr?.inferType(expected))
blockTys.add(elseBranch.block?.inferType(expected))
}
return if (expr.elseBranch == null) TyUnit else getMoreCompleteType(blockTys.filterNotNull())
}
private fun RsCondition.inferTypes() {
val orPats = orPats
if (orPats != null) {
// if let Some(a) = ... {}
// if let V1(a) | V2(a) = ... {}
// or
// while let Some(a) = ... {}
// while let V1(a) | V2(a) = ... {}
val exprTy = resolveTypeVarsWithObligations(expr.inferType())
orPats.extractBindings(exprTy)
} else {
expr.inferType(TyBool)
}
}
private fun inferBinaryExprType(expr: RsBinaryExpr): Ty {
val lhsType = resolveTypeVarsWithObligations(expr.left.inferType())
val op = expr.operatorType
val (rhsType, retTy) = when (op) {
is BoolOp -> {
if (op is OverloadableBinaryOperator) {
val rhsTypeVar = TyInfer.TyVar()
enforceOverloadedBinopTypes(lhsType, rhsTypeVar, op)
val rhsType = resolveTypeVarsWithObligations(expr.right?.inferTypeCoercableTo(rhsTypeVar)
?: TyUnknown)
val lhsAdjustment = Adjustment.BorrowReference(TyReference(lhsType, Mutability.IMMUTABLE))
ctx.addAdjustment(expr.left, lhsAdjustment)
val rhsAdjustment = Adjustment.BorrowReference(TyReference(rhsType, Mutability.IMMUTABLE))
expr.right?.let { ctx.addAdjustment(it, rhsAdjustment) }
rhsType to TyBool
} else {
val rhsType = resolveTypeVarsWithObligations(expr.right?.inferTypeCoercableTo(lhsType) ?: TyUnknown)
rhsType to TyBool
}
}
is ArithmeticOp -> {
val rhsTypeVar = TyInfer.TyVar()
val retTy = lookup.findArithmeticBinaryExprOutputType(lhsType, rhsTypeVar, op)?.register() ?: TyUnknown
val rhsType = resolveTypeVarsWithObligations(expr.right?.inferTypeCoercableTo(rhsTypeVar) ?: TyUnknown)
rhsType to retTy
}
is ArithmeticAssignmentOp -> {
val rhsTypeVar = TyInfer.TyVar()
enforceOverloadedBinopTypes(lhsType, rhsTypeVar, op)
val rhsType = resolveTypeVarsWithObligations(expr.right?.inferTypeCoercableTo(rhsTypeVar) ?: TyUnknown)
val lhsAdjustment = Adjustment.BorrowReference(TyReference(lhsType, Mutability.MUTABLE))
ctx.addAdjustment(expr.left, lhsAdjustment)
rhsType to TyUnit
}
AssignmentOp.EQ -> {
val rhsType = expr.right?.inferTypeCoercableTo(lhsType) ?: TyUnknown
rhsType to TyUnit
}
}
if (op != AssignmentOp.EQ && isBuiltinBinop(lhsType, rhsType, op)) {
val builtinRetTy = enforceBuiltinBinopTypes(lhsType, rhsType, op)
if (op !is ArithmeticAssignmentOp) {
ctx.combineTypes(builtinRetTy, retTy)
}
}
return retTy
}
private fun enforceOverloadedBinopTypes(lhsType: Ty, rhsType: Ty, op: OverloadableBinaryOperator) {
selectOverloadedOp(lhsType, rhsType, op)?.let { fulfill.registerPredicateObligation(it) }
}
private fun selectOverloadedOp(lhsType: Ty, rhsType: Ty, op: OverloadableBinaryOperator): Obligation? {
val trait = op.findTrait(items) ?: return null
return Obligation(Predicate.Trait(TraitRef(lhsType, trait.withSubst(rhsType))))
}
private fun isBuiltinBinop(lhsType: Ty, rhsType: Ty, op: BinaryOperator): Boolean = when (op.category) {
BinOpCategory.Shortcircuit -> true
BinOpCategory.Shift -> lhsType.isIntegral && rhsType.isIntegral
BinOpCategory.Math -> lhsType.isIntegral && rhsType.isIntegral ||
lhsType.isFloat && rhsType.isFloat
BinOpCategory.Bitwise -> lhsType.isIntegral && rhsType.isIntegral ||
lhsType.isFloat && rhsType.isFloat ||
lhsType == TyBool && rhsType == TyBool
BinOpCategory.Comparison -> lhsType.isScalar && rhsType.isScalar
}
private fun enforceBuiltinBinopTypes(lhsType: Ty, rhsType: Ty, op: BinaryOperator): Ty = when (op.category) {
BinOpCategory.Shortcircuit -> {
ctx.combineTypes(lhsType, TyBool)
ctx.combineTypes(lhsType, TyBool)
TyBool
}
BinOpCategory.Shift -> lhsType
BinOpCategory.Math, BinOpCategory.Bitwise -> {
ctx.combineTypes(lhsType, rhsType)
lhsType
}
BinOpCategory.Comparison -> {
ctx.combineTypes(lhsType, rhsType)
TyBool
}
}
private fun inferTryExprType(expr: RsTryExpr): Ty {
val base = expr.expr.inferType() as? TyAdt ?: return TyUnknown
// TODO: make it work with generic `std::ops::Try` trait
if (base.item != items.Result && base.item != items.Option) return TyUnknown
TypeInferenceMarks.questionOperator.hit()
return base.typeArguments.getOrElse(0) { TyUnknown }
}
private fun inferTryMacroArgumentType(expr: RsExpr): Ty {
val base = expr.inferType() as? TyAdt ?: return TyUnknown
if (base.item != items.Result) return TyUnknown
return base.typeArguments.firstOrNull() ?: TyUnknown
}
private fun inferRangeType(expr: RsRangeExpr): Ty {
val el = expr.exprList
val dot2 = expr.dotdot
val dot3 = expr.dotdotdot ?: expr.dotdoteq
val (rangeName, indexType) = when {
dot2 != null && el.size == 0 -> "RangeFull" to null
dot2 != null && el.size == 1 -> {
val e = el[0]
if (e.startOffsetInParent < dot2.startOffsetInParent) {
"RangeFrom" to e.inferType()
} else {
"RangeTo" to e.inferType()
}
}
dot2 != null && el.size == 2 -> {
"Range" to getMoreCompleteType(el[0].inferType(), el[1].inferType())
}
dot3 != null && el.size == 1 -> {
val e = el[0]
if (e.startOffsetInParent < dot3.startOffsetInParent) {