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Introduce scanning fast paths #59244

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Introduce scanning fast paths #59244

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18df637
Move shebang check into the same branch as other `#` cases.
DanielRosenwasser Jul 11, 2024
bc21cdd
Add a quicker check for identifiers, check for space sooner.
DanielRosenwasser Jul 11, 2024
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38 changes: 21 additions & 17 deletions src/compiler/scanner.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1882,17 +1882,10 @@ export function createScanner(languageVersion: ScriptTarget, skipTrivia: boolean
}

const ch = codePointUnchecked(pos);
if (pos === 0) {
// Special handling for shebang
if (ch === CharacterCodes.hash && isShebangTrivia(text, pos)) {
pos = scanShebangTrivia(text, pos);
if (skipTrivia) {
continue;
}
else {
return token = SyntaxKind.ShebangTrivia;
}
}

if (CharacterCodes.a <= (ch | 32) && (ch | 32) <= CharacterCodes.z) {
const identifierKind = scanIdentifier(ch, languageVersion);
return identifierKind!;
}

switch (ch) {
Expand All @@ -1913,10 +1906,10 @@ export function createScanner(languageVersion: ScriptTarget, skipTrivia: boolean
}
return token = SyntaxKind.NewLineTrivia;
}
case CharacterCodes.space:
case CharacterCodes.tab:
case CharacterCodes.verticalTab:
case CharacterCodes.formFeed:
case CharacterCodes.space:
case CharacterCodes.nonBreakingSpace:
case CharacterCodes.ogham:
case CharacterCodes.enQuad:
Expand Down Expand Up @@ -2302,13 +2295,24 @@ export function createScanner(languageVersion: ScriptTarget, skipTrivia: boolean
pos++;
return token = SyntaxKind.Unknown;
case CharacterCodes.hash:
if (pos !== 0 && text[pos + 1] === "!") {
error(Diagnostics.can_only_be_used_at_the_start_of_a_file, pos, 2);
pos++;
return token = SyntaxKind.Unknown;
// Special handling for shebang
const charAfterHash = codePointUnchecked(pos + 1);
if (charAfterHash === CharacterCodes.exclamation) {
if (pos !== 0) {
error(Diagnostics.can_only_be_used_at_the_start_of_a_file, pos, 2);
pos++;
return token = SyntaxKind.Unknown;
}

pos = scanShebangTrivia(text, pos);
if (skipTrivia) {
continue;
}
else {
return token = SyntaxKind.ShebangTrivia;
}
}

const charAfterHash = codePointUnchecked(pos + 1);
if (charAfterHash === CharacterCodes.backslash) {
pos++;
const extendedCookedChar = peekExtendedUnicodeEscape();
Expand Down