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Fix parsing error in exponent expressions with unary left-hand sides.
Esprima (correctly) rejects expressions like -1**2. However, expressions like (-1)**2 are valid but still rejected. This commit fixes this issue by identifying when the left operand is parenthesized. Fixes jquery#1981
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3 files changed

+250
-1
lines changed

3 files changed

+250
-1
lines changed

‎src/parser.ts

+9-1
Original file line numberDiff line numberDiff line change
@@ -1475,8 +1475,16 @@ export class Parser {
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parseExponentiationExpression(): Node.Expression {
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const startToken = this.lookahead;
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// -1 ** 2 is not accepted, but (-1) ** 2
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// However, the AST for both cases is identical
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// We distinguish the two cases by explicitly checking for a parenthesis.
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const isLeftParenthesized = this.match('(');
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let expr = this.inheritCoverGrammar(this.parseUnaryExpression);
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if (expr.type !== Syntax.UnaryExpression && this.match('**')) {
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const exponentAllowed = expr.type !== Syntax.UnaryExpression || isLeftParenthesized;
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if (exponentAllowed && this.match('**')) {
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this.nextToken();
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this.context.isAssignmentTarget = false;
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this.context.isBindingElement = false;

‎test/fixtures/ES2016/exponent/exp_paren.js

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
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(-2) ** 1;

‎test/fixtures/ES2016/exponent/exp_paren.tree.json

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@@ -0,0 +1,240 @@
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{
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"type": "Program",
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"body": [
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{
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"type": "ExpressionStatement",
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"expression": {
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"type": "BinaryExpression",
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"operator": "**",
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"left": {
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"type": "UnaryExpression",
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"operator": "-",
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"argument": {
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"type": "Literal",
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"value": 2,
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"raw": "2",
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"range": [
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2,
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3
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 2
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},
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"end": {
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"line": 1,
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"column": 3
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}
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}
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},
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"prefix": true,
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"range": [
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1,
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3
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 1
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},
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"end": {
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"line": 1,
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"column": 3
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}
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}
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},
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"right": {
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"type": "Literal",
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"value": 1,
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"raw": "1",
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"range": [
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8,
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9
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 8
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},
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"end": {
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"line": 1,
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"column": 9
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}
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}
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},
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"range": [
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0,
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9
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 0
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},
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"end": {
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"line": 1,
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"column": 9
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}
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}
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},
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"range": [
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0,
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10
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 0
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},
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"end": {
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"line": 1,
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"column": 10
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}
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}
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}
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],
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"sourceType": "script",
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"range": [
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0,
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10
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 0
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},
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"end": {
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"line": 1,
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"column": 10
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}
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},
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"tokens": [
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{
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"type": "Punctuator",
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"value": "(",
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"range": [
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0,
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1
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 0
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},
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"end": {
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"line": 1,
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"column": 1
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}
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}
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},
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{
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"type": "Punctuator",
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"value": "-",
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"range": [
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1,
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2
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 1
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},
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"end": {
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"line": 1,
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"column": 2
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}
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}
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},
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{
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"type": "Numeric",
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"value": "2",
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"range": [
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2,
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3
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 2
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},
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"end": {
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"line": 1,
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"column": 3
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}
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}
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},
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{
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"type": "Punctuator",
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"value": ")",
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"range": [
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3,
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4
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 3
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},
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"end": {
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"line": 1,
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"column": 4
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}
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}
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},
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{
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"type": "Punctuator",
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"value": "**",
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"range": [
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5,
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7
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 5
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},
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"end": {
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"line": 1,
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"column": 7
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}
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}
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},
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{
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"type": "Numeric",
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"value": "1",
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"range": [
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8,
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9
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 8
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},
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"end": {
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"line": 1,
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"column": 9
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}
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}
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},
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{
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"type": "Punctuator",
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"value": ";",
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"range": [
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9,
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10
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],
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"loc": {
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"start": {
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"line": 1,
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"column": 9
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},
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"end": {
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"line": 1,
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"column": 10
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}
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}
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}
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]
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}

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