XType.kt
/*
* Copyright (C) 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.room.compiler.processing
import com.squareup.javapoet.ClassName
import com.squareup.javapoet.TypeName
import kotlin.contracts.contract
import kotlin.reflect.KClass
/**
* Represents a type reference
*
* @see javax.lang.model.type.TypeMirror
* @see [XArrayType]
*/
interface XType {
/**
* The Javapoet [TypeName] representation of the type
*/
val typeName: TypeName
/**
* Returns the rawType of this type. (e.g. `List<String>` to `List`.
*/
val rawType: XRawType
/**
* Nullability declared in the code.
* For Kotlin types, it will be inferred from type declaration.
* For Java types, it will be inferred from annotations.
*/
val nullability: XNullability
/**
* The [XTypeElement] that represents this type.
*
* Note that it might be null if the type is not backed by a type element (e.g. if it is a
* primitive, wildcard etc)
*
* @see isTypeElement
*/
val typeElement: XTypeElement?
/**
* Type arguments for the element. Note that they might be either placeholders or real
* resolvable types depending on the usage.
*
* If the type is not declared (e.g. a primitive), the list is empty.
*
* @see [javax.lang.model.type.DeclaredType.getTypeArguments]
*/
val typeArguments: List<XType>
/**
* Returns `true` if this type can be assigned from [other]
*/
fun isAssignableFrom(other: XType): Boolean
/**
* Returns `true` if this can be assigned from an instance of [other] without checking for
* variance.
*/
fun isAssignableFromWithoutVariance(other: XType): Boolean {
return isAssignableWithoutVariance(other, this)
}
// TODO these is<Type> checks may need to be moved into the implementation.
// It is not yet clear how we will model some types in Kotlin (e.g. primitives)
/**
* Returns `true` if this is an error type.
*/
fun isError(): Boolean
/**
* Returns the string representation of a possible default value for this type.
* (e.g. `0` for `int`, `null` for `String`)
*/
fun defaultValue(): String
/**
* Returns boxed version of this type if it is a primitive or itself if it is not a primitive
* type.
*/
fun boxed(): XType
/**
* Returns `true` if this is a [List]
*/
fun isList(): Boolean = isTypeOf(List::class)
/**
* Returns `true` if this is the None type.
*/
fun isNone(): Boolean
/**
* Returns `true` if this is the same raw type as [other]
*/
fun isTypeOf(other: KClass<*>): Boolean
/**
* Returns `true` if this represents the same type as [other].
* TODO: decide on how we want to handle nullability here.
*/
fun isSameType(other: XType): Boolean
/**
* Returns the extends bound if this is a wildcard or self.
*/
fun extendsBoundOrSelf(): XType = extendsBound() ?: this
/**
* If this is a wildcard with an extends bound, returns that bounded typed.
*/
fun extendsBound(): XType?
/**
* Creates a type with nullability [XNullability.NULLABLE] or returns this if the nullability is
* already [XNullability.NULLABLE].
*/
fun makeNullable(): XType
/**
* Creates a type with nullability [XNullability.NONNULL] or returns this if the nullability is
* already [XNullability.NONNULL].
*/
fun makeNonNullable(): XType
}
/**
* Returns true if this is an [XArrayType].
*/
fun XType.isArray(): Boolean {
contract {
returns(true) implies (this@isArray is XArrayType)
}
return this is XArrayType
}
/**
* Returns true if this is a [List] or [Set].
*/
fun XType.isCollection(): Boolean {
return isTypeOf(List::class) || isTypeOf(Set::class)
}
private fun isAssignableWithoutVariance(from: XType, to: XType): Boolean {
val assignable = to.isAssignableFrom(from)
if (assignable) {
return true
}
val fromTypeArgs = from.typeArguments
val toTypeArgs = to.typeArguments
// no type arguments, we don't need extra checks
if (fromTypeArgs.isEmpty() || fromTypeArgs.size != toTypeArgs.size) {
return false
}
// check erasure version first, if it does not match, no reason to proceed
if (!to.rawType.isAssignableFrom(from)) {
return false
}
// convert from args to their upper bounds if it exists
val fromExtendsBounds = fromTypeArgs.map {
it.extendsBound()
}
// if there are no upper bound conversions, return.
if (fromExtendsBounds.all { it == null }) {
return false
}
// try to move the types of the from to their upper bounds. It does not matter for the "to"
// because Types.isAssignable handles it as it is valid java
return (fromTypeArgs.indices).all { index ->
isAssignableWithoutVariance(
from = fromExtendsBounds[index] ?: fromTypeArgs[index],
to = toTypeArgs[index]
)
}
}
/**
* Returns `true` if this is a primitive or boxed it
*/
fun XType.isInt(): Boolean = typeName == TypeName.INT || typeName == KnownTypeNames.BOXED_INT
/**
* Returns `true` if this is a primitive or boxed long
*/
fun XType.isLong(): Boolean = typeName == TypeName.LONG || typeName == KnownTypeNames.BOXED_LONG
/**
* Returns `true` if this is `void`
*/
fun XType.isVoid() = typeName == TypeName.VOID
/**
* Returns `true` if this is a [Void]
*/
fun XType.isVoidObject(): Boolean = typeName == KnownTypeNames.BOXED_VOID
/**
* Returns `true` if this is the kotlin [Unit] type.
*/
fun XType.isKotlinUnit(): Boolean = typeName == KnownTypeNames.KOTLIN_UNIT
/**
* Returns `true` if this represents a `byte`.
*/
fun XType.isByte(): Boolean = typeName == TypeName.BYTE || typeName == KnownTypeNames.BOXED_BYTE
internal object KnownTypeNames {
val BOXED_VOID = TypeName.VOID.box()
val BOXED_INT = TypeName.INT.box()
val BOXED_LONG = TypeName.LONG.box()
val BOXED_BYTE = TypeName.BYTE.box()
val KOTLIN_UNIT = ClassName.get("kotlin", "Unit")
}