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fix: Align the ASI behaviour with typescript #3053

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fix: Align the ASI behaviour with typescript #3053

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696e6b7
WIP
Changqing-JING Oct 17, 2026
6021ab6
add test
Changqing-JING Oct 20, 2026
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96 changes: 64 additions & 32 deletions src/parser.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -649,7 +649,7 @@ export class Parser extends DiagnosticEmitter {
let parameters: TypeNode[] | null = null;

// Name<T>
if (tn.skip(Token.LessThan)) {
if (!tn.peekOnNewLine() && tn.skip(Token.LessThan)) {

@JairusSW JairusSW Nov 13, 2026

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This might affect generics (< token) when it's on a new line. For example,

class Foo<T> {}
class Bar extends Foo
<string> {}

should fail i think?

do {
let parameter = this.parseType(tn, true, suppressErrors);
if (!parameter) return null;
Expand Down Expand Up @@ -703,7 +703,7 @@ export class Parser extends DiagnosticEmitter {
}
}
// ... [][]
while (tn.skip(Token.OpenBracket)) {
while (!tn.peekOnNewLine() && tn.skip(Token.OpenBracket)) {
let bracketStart = tn.tokenPos;
if (!tn.skip(Token.CloseBracket)) {
if (!suppressErrors) {
Expand Down Expand Up @@ -991,7 +991,8 @@ export class Parser extends DiagnosticEmitter {
} while (tn.skip(Token.Comma));

let ret = Node.createVariableStatement(decorators, declarations, tn.range(startPos, tn.pos));
if (!tn.skip(Token.Semicolon) && !isFor) this.checkASI(tn);
if (isFor) tn.skip(Token.Semicolon);
else this.parseSemicolon(tn);
return ret;
}

Expand Down Expand Up @@ -1019,7 +1020,8 @@ export class Parser extends DiagnosticEmitter {
);
}
let flags = parentFlags;
if (tn.skip(Token.Exclamation)) {
if (tn.peek() == Token.Exclamation && !tn.peekOnNewLine()) {
tn.next();
flags |= CommonFlags.DefinitelyAssigned;
}

Expand Down Expand Up @@ -1175,7 +1177,7 @@ export class Parser extends DiagnosticEmitter {
}

let ret = Node.createReturnStatement(expr, tn.range(startPos, tn.pos));
if (!tn.skip(Token.Semicolon)) this.checkASI(tn);
this.parseSemicolon(tn);
return ret;
}

Expand Down Expand Up @@ -1601,7 +1603,8 @@ export class Parser extends DiagnosticEmitter {
tn.range(startPos, tn.pos)
);
ret.overriddenModuleName = this.currentModuleName;
tn.skip(Token.Semicolon);
if (body) tn.skip(Token.Semicolon);
else this.parseSemicolon(tn);
return ret;
}

Expand Down Expand Up @@ -1669,6 +1672,13 @@ export class Parser extends DiagnosticEmitter {
}

if (arrowKind) {
if (tn.peek() == Token.Equals_GreaterThan && tn.peekOnNewLine()) {
this.error(
DiagnosticCode.Unexpected_token,
tn.range(tn.nextTokenPos)
);
return null;
}
if (!tn.skip(Token.Equals_GreaterThan)) {
this.error(
DiagnosticCode._0_expected,
Expand Down Expand Up @@ -2203,7 +2213,7 @@ export class Parser extends DiagnosticEmitter {
}
return null;
}
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return retIndex;
}
if (!tn.skipIdentifier(IdentifierHandling.Always)) {
Expand Down Expand Up @@ -2367,8 +2377,10 @@ export class Parser extends DiagnosticEmitter {
body,
tn.range(startPos, tn.pos)
);
if (!(isInterface && tn.skip(Token.Comma))) {
tn.skip(Token.Semicolon);
let hasComma = isInterface && tn.skip(Token.Comma);
if (!hasComma) {
if (body) tn.skip(Token.Semicolon);
else this.parseSemicolon(tn);
}
return retMethod;

Expand Down Expand Up @@ -2421,7 +2433,8 @@ export class Parser extends DiagnosticEmitter {
tn.range(startPos, tn.pos)
);
}
if (tn.skip(Token.Exclamation)) {
if (tn.peek() == Token.Exclamation && !tn.peekOnNewLine()) {
tn.next();
flags |= CommonFlags.DefinitelyAssigned;
}
if (tn.skip(Token.Colon)) {
Expand Down Expand Up @@ -2465,9 +2478,7 @@ export class Parser extends DiagnosticEmitter {
initializer,
range
);
if (!(isInterface && tn.skip(Token.Comma))) {
tn.skip(Token.Semicolon);
}
if (!(isInterface && tn.skip(Token.Comma))) this.parseSemicolon(tn);
return retField;
}
return null;
Expand Down Expand Up @@ -2656,7 +2667,7 @@ export class Parser extends DiagnosticEmitter {
this.seenlog.add(internalPath);
}
}
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
} else if (tn.skip(Token.Asterisk)) {
if (tn.skip(Token.From)) {
Expand All @@ -2672,7 +2683,7 @@ export class Parser extends DiagnosticEmitter {
this.dependees.set(internalPath, new Dependee(currentSource, path));
this.backlog.push(internalPath);
}
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
} else {
this.error(
Expand Down Expand Up @@ -2754,7 +2765,7 @@ export class Parser extends DiagnosticEmitter {
range
)
], null, false, tn.range(startPos, tn.pos));
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
}

Expand Down Expand Up @@ -2844,7 +2855,7 @@ export class Parser extends DiagnosticEmitter {
this.dependees.set(internalPath, new Dependee(assert(this.currentSource), path));
this.backlog.push(internalPath);
}
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
} else {
this.error(
Expand Down Expand Up @@ -2915,7 +2926,7 @@ export class Parser extends DiagnosticEmitter {
if (tn.skipIdentifier()) {
let identifier = Node.createIdentifierExpression(tn.readIdentifier(), tn.range());
let ret = Node.createExportImportStatement(identifier, asIdentifier, tn.range(startPos, tn.pos));
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
} else {
this.error(
Expand Down Expand Up @@ -3078,7 +3089,7 @@ export class Parser extends DiagnosticEmitter {
identifier = Node.createIdentifierExpression(tn.readIdentifier(), tn.range());
}
let ret = Node.createBreakStatement(identifier, tn.range());
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
}

Expand All @@ -3094,7 +3105,7 @@ export class Parser extends DiagnosticEmitter {
identifier = Node.createIdentifierExpression(tn.readIdentifier(), tn.range());
}
let ret = Node.createContinueStatement(identifier, tn.range());
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
}

Expand Down Expand Up @@ -3140,7 +3151,8 @@ export class Parser extends DiagnosticEmitter {
}

parseExpressionStatement(
tn: Tokenizer
tn: Tokenizer,
isFor: bool = false
): ExpressionStatement | null {

// at previous token
Expand All @@ -3149,7 +3161,8 @@ export class Parser extends DiagnosticEmitter {
if (!expr) return null;

let ret = Node.createExpressionStatement(expr);
tn.skip(Token.Semicolon);
if (isFor) tn.skip(Token.Semicolon);
else this.parseSemicolon(tn);

@JairusSW JairusSW Nov 13, 2026

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Wouldn't isFor not fire in a nested func declaration?
eg.

export function foo(): i32 {
  function bar(): i32 { return 42; } return bar();
}

on my end, it panics when a nested function is followed by a statement on the same line as the closing brace.

return ret;
}

Expand All @@ -3172,7 +3185,7 @@ export class Parser extends DiagnosticEmitter {
initializer = this.parseVariable(tn, CommonFlags.None, null, tn.tokenPos, true);

} else if (!tn.skip(Token.Semicolon)) {
initializer = this.parseExpressionStatement(tn);
initializer = this.parseExpressionStatement(tn, true);
if (!initializer) return null;
}

Expand Down Expand Up @@ -3234,7 +3247,7 @@ export class Parser extends DiagnosticEmitter {
if (tn.token == Token.Semicolon) {
let condition: ExpressionStatement | null = null;
if (!tn.skip(Token.Semicolon)) {
condition = this.parseExpressionStatement(tn);
condition = this.parseExpressionStatement(tn, true);
if (!condition) return null;
}

Expand Down Expand Up @@ -3375,7 +3388,6 @@ export class Parser extends DiagnosticEmitter {
switchCases.push(switchCase);
}
let ret = Node.createSwitchStatement(condition, switchCases, tn.range(startPos, tn.pos));
tn.skip(Token.Semicolon);
return ret;
} else {
this.error(
Expand Down Expand Up @@ -3467,10 +3479,17 @@ export class Parser extends DiagnosticEmitter {
// at 'throw': Expression ';'?

let startPos = tn.tokenPos;
if (tn.peekOnNewLine()) {
this.error(
DiagnosticCode.Unexpected_token,
tn.range(tn.nextTokenPos)
);
return null;
}
let expression = this.parseExpression(tn);
if (!expression) return null;
let ret = Node.createThrowStatement(expression, tn.range(startPos, tn.pos));
if (!tn.skip(Token.Semicolon)) this.checkASI(tn);
this.parseSemicolon(tn);
return ret;
}

Expand Down Expand Up @@ -3561,7 +3580,6 @@ export class Parser extends DiagnosticEmitter {
finallyStatements,
tn.range(startPos, tn.pos)
);
tn.skip(Token.Semicolon);
return ret;
} else {
this.error(
Expand Down Expand Up @@ -3608,7 +3626,7 @@ export class Parser extends DiagnosticEmitter {
type,
tn.range(startPos, tn.pos)
);
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
ret.overriddenModuleName = this.currentModuleName;
return ret;
} else {
Expand Down Expand Up @@ -3638,7 +3656,7 @@ export class Parser extends DiagnosticEmitter {
let moduleName = tn.readString();
let ret = Node.createModuleDeclaration(moduleName, flags, tn.range(startPos, tn.pos));
this.currentModuleName = moduleName;
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
}

Expand All @@ -3649,10 +3667,10 @@ export class Parser extends DiagnosticEmitter {
// at 'void': Expression ';'?

let startPos = tn.tokenPos;
let expression = this.parseExpression(tn, Precedence.Grouping);
let expression = this.parseExpression(tn, Precedence.UnaryPrefix);
if (!expression) return null;
let ret = Node.createVoidStatement(expression, tn.range(startPos, tn.pos));
tn.skip(Token.Semicolon);
this.parseSemicolon(tn);
return ret;
}

Expand All @@ -3670,7 +3688,6 @@ export class Parser extends DiagnosticEmitter {
let statement = this.parseStatement(tn);
if (!statement) return null;
let ret = Node.createWhileStatement(expression, statement, tn.range(startPos, tn.pos));
tn.skip(Token.Semicolon);
return ret;
} else {
this.error(
Expand Down Expand Up @@ -4131,6 +4148,15 @@ export class Parser extends DiagnosticEmitter {
while (
(nextPrecedence = determinePrecedence(tn.peek())) >= precedence
) {
let nextToken = tn.peek();
if (
(
nextToken == Token.Plus_Plus ||
nextToken == Token.Minus_Minus ||
nextToken == Token.As ||
nextToken == Token.Exclamation
) && tn.peekOnNewLine()
) break;
let token = tn.next();
switch (token) {

Expand Down Expand Up @@ -4430,6 +4456,12 @@ export class Parser extends DiagnosticEmitter {
);
}

private parseSemicolon(
tn: Tokenizer
): void {
if (!tn.skip(Token.Semicolon)) this.checkASI(tn);
}

/** Skips over a statement on errors in an attempt to reduce unnecessary diagnostic noise. */
skipStatement(tn: Tokenizer): void {
if (tn.peekOnNewLine()) tn.next(); // if reset() to the previous line
Expand Down
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