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72 lines
1.7 KiB
JavaScript
72 lines
1.7 KiB
JavaScript
"use strict";
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const GrammarError = require( "../../grammar-error" );
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const visitor = require( "../visitor" );
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const util = require( "../../util" );
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const __hasOwnProperty = Object.prototype.hasOwnProperty;
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// Checks that each label is defined only once within each scope.
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function reportDuplicateLabels( ast ) {
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let check;
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function checkExpressionWithClonedEnv( node, env ) {
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check( node.expression, util.clone( env ) );
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}
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check = visitor.build( {
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rule( node ) {
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check( node.expression, {} );
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},
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choice( node, env ) {
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node.alternatives.forEach( alternative => {
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check( alternative, util.clone( env ) );
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} );
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},
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action: checkExpressionWithClonedEnv,
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labeled( node, env ) {
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const label = node.label;
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if ( __hasOwnProperty.call( env, label ) ) {
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const start = env[ label ].start;
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throw new GrammarError(
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`Label "${ label }" is already defined at line ${ start.line }, column ${ start.column }.`,
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node.location
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);
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}
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check( node.expression, env );
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env[ label ] = node.location;
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},
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text: checkExpressionWithClonedEnv,
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simple_and: checkExpressionWithClonedEnv,
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simple_not: checkExpressionWithClonedEnv,
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optional: checkExpressionWithClonedEnv,
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zero_or_more: checkExpressionWithClonedEnv,
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one_or_more: checkExpressionWithClonedEnv,
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group: checkExpressionWithClonedEnv
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} );
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check( ast );
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}
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module.exports = reportDuplicateLabels;
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