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37 lines
960 B
JavaScript
37 lines
960 B
JavaScript
// @flow
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import type {Expression} from './expression.js';
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/**
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* Tracks `let` bindings during expression parsing.
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* @private
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*/
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class Scope {
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parent: ?Scope;
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bindings: {[_: string]: Expression};
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constructor(parent?: Scope, bindings: Array<[string, Expression]> = []) {
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this.parent = parent;
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this.bindings = {};
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for (const [name, expression] of bindings) {
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this.bindings[name] = expression;
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}
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}
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concat(bindings: Array<[string, Expression]>): Scope {
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return new Scope(this, bindings);
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}
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get(name: string): Expression {
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if (this.bindings[name]) { return this.bindings[name]; }
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if (this.parent) { return this.parent.get(name); }
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throw new Error(`${name} not found in scope.`);
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}
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has(name: string): boolean {
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if (this.bindings[name]) return true;
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return this.parent ? this.parent.has(name) : false;
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}
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}
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export default Scope;
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