| /* |
| * 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 NullType extends Type { |
| constructor(origin) |
| { |
| super(); |
| this._origin = origin; |
| } |
| |
| get origin() { return this._origin; } |
| |
| // For now we answer false for isPtr and isArrayRef because that happens to make all of the logic |
| // work. But, it's strange, since as a bottom type it really is the case that this is both isPtr and |
| // isArrayRef. |
| |
| get isPrimitive() { return true; } |
| get isUnifiable() { return true; } |
| get isLiteral() { return true; } |
| |
| 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); |
| if (realThis.isPtr || realThis.isArrayRef) |
| return {result: true}; |
| return {result: false, reason: "Null cannot be used with non-pointer type " + realThis}; |
| } |
| |
| verifyAsParameter(unificationContext) |
| { |
| throw new Error("NullType should never be used as a type parameter"); |
| } |
| |
| commitUnification(unificationContext) |
| { |
| this.type = unificationContext.find(this); |
| } |
| |
| toString() |
| { |
| return "nullType"; |
| } |
| } |
| |