| /* |
| * Copyright (C) 2017 Apple Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY |
| * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR |
| * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY |
| * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| "use strict"; |
| |
| class TypeVariable extends Type { |
| constructor(origin, name, protocol) |
| { |
| super(); |
| this._origin = origin; |
| this._name = name; |
| this._protocol = protocol; |
| } |
| |
| get origin() { return this._origin; } |
| get name() { return this._name; } |
| get protocol() { return this._protocol; } |
| |
| get isPrimitive() |
| { |
| return this._protocol && this._protocol.isPrimitive; |
| } |
| |
| get isUnifiable() { return true; } |
| |
| inherits(protocol) |
| { |
| if (!protocol) |
| return {result: true}; |
| if (!this.protocol) |
| return {result: false, reason: "Type variable " + this + " does not have a protocol"}; |
| return this.protocol.inherits(protocol); |
| } |
| |
| typeVariableUnify(unificationContext, other) |
| { |
| if (!(other instanceof Type)) |
| return false; |
| |
| return this._typeVariableUnifyImpl(unificationContext, other); |
| } |
| |
| unifyImpl(unificationContext, other) |
| { |
| return this.typeVariableUnify(unificationContext, other); |
| } |
| |
| verifyAsArgument(unificationContext) |
| { |
| let realThis = unificationContext.find(this); |
| |
| // The thing we get unified with must be a type variable that accepts a broader set of |
| // things than we do. |
| if (!(realThis instanceof TypeVariable)) |
| return {result: false, reason: "Type variable argument " + this + " cannot be passed to non-type-variable parameter type " + realThis}; |
| |
| if (!this.protocol) { |
| if (realThis.protocol) |
| return {result: false, reason: "Type variable without protocol " + this + " cannot be passed to parameter type variable with protocol " + realThis.protocol}; |
| return {result: true}; |
| } |
| |
| let result = this.protocol.inherits(realThis.protocol); |
| if (!result.result) |
| return {result: false, reason: "Protocol " + this.protocol + " does not subsume protocol " + realThis.protocol + " (passing type " + this + " to type " + realThis + "): " + result.reason}; |
| return {result: true}; |
| } |
| |
| verifyAsParameter(unificationContext) |
| { |
| if (!this.protocol) |
| return {result: true}; |
| let realThis = unificationContext.find(this); |
| let result = realThis.inherits(this.protocol); |
| if (!result.result) |
| return {result: false, reason: "Type " + realThis + " does not inherit protocol " + this.protocol + " (passing type " + realThis + " to type " + this + "): " + result.reason}; |
| return {result: true}; |
| } |
| |
| toString() |
| { |
| return this.name + (this.protocol ? ":" + this.protocol.name : ""); |
| } |
| } |
| |