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Fix await using double lookahead edge case #1382

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Merged
merged 2 commits into from
Jul 8, 2025
+11 −8
Merged

Fix await using double lookahead edge case #1382

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0ee7596
Rename confusing variable name
adams85 Jul 7, 2025
b45f21e
Fix await using double lookahead edge case
adams85 Jul 7, 2025
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16 changes: 8 additions & 8 deletions acorn/src/statement.js
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Original file line number Diff line number Diff line change
Expand Up @@ -84,17 +84,17 @@ pp.isUsingKeyword = function(isAwaitUsing, isFor) {
if (lineBreak.test(this.input.slice(this.pos, next))) return false

if (isAwaitUsing) {
let awaitEndPos = next + 5 /* await */, after
if (this.input.slice(next, awaitEndPos) !== "using" ||
awaitEndPos === this.input.length ||
isIdentifierChar(after = this.input.charCodeAt(awaitEndPos)) ||
(after > 0xd7ff && after < 0xdc00)
let usingEndPos = next + 5 /* using */, after
if (this.input.slice(next, usingEndPos) !== "using" ||
usingEndPos === this.input.length ||
isIdentifierChar(after = this.fullCharCodeAt(usingEndPos)) ||
after === 92 /* '\' */
) return false

skipWhiteSpace.lastIndex = awaitEndPos
skipWhiteSpace.lastIndex = usingEndPos
let skipAfterUsing = skipWhiteSpace.exec(this.input)
next = awaitEndPos + skipAfterUsing[0].length
if (skipAfterUsing && lineBreak.test(this.input.slice(awaitEndPos, next))) return false
next = usingEndPos + skipAfterUsing[0].length
if (skipAfterUsing && lineBreak.test(this.input.slice(usingEndPos, next))) return false
}

let ch = this.fullCharCodeAt(next)
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3 changes: 3 additions & 0 deletions test/tests-using.js
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Expand Up @@ -1184,6 +1184,9 @@ testFail("for (await using a of x) {}", "Await using cannot appear outside of as
testFail("switch (x) { case 1: using y = resource; }", "Using declaration cannot appear in the top level when source type is `script` or in the bare case statement (1:21)", {ecmaVersion: 17, sourceType: "module"});
testFail("switch (x) { case 1: break; default: using y = resource; }", "Using declaration cannot appear in the top level when source type is `script` or in the bare case statement (1:37)", {ecmaVersion: 17, sourceType: "module"});

// await using double lookahead should detect using keyword correctly
testFail("async () => { await using\\u0061 b = c }", "Unexpected token (1:32)", {ecmaVersion: 17, sourceType: "module"});

// =============================================================================
// EDGE CASES - Unusual but valid scenarios and boundary conditions
// =============================================================================
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