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Re-scan '<<' when parsing type arguments in heritage clauses, typeof queries, and JSX #64716

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Re-scan '<<' when parsing type arguments in heritage clauses, typeof queries, and JSX #64716

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e91e142
Add test for type arguments starting with '<<'
ahmad65saad Oct 10, 2026
7f7a621
Re-scan '<<' when parsing type arguments
ahmad65saad Oct 10, 2026
65e2afc
Add JSDoc @augments/@implements case with a generic function type arg…
ahmad65saad Oct 10, 2026
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16 changes: 14 additions & 2 deletions tsc/internal/parser/parser.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3086,7 +3086,7 @@ func (p *Parser) parseTypeArgumentsOfTypeReference() *ast.NodeList {
}

func (p *Parser) parseTypeArguments() *ast.NodeList {
if p.token == ast.KindLessThanToken {
if p.reScanLessThanToken() == ast.KindLessThanToken {
return p.parseBracketedList(PCTypeArguments, (*Parser).parseType, ast.KindLessThanToken, ast.KindGreaterThanToken)
}
return nil
Expand Down Expand Up @@ -3189,7 +3189,19 @@ func (p *Parser) parseTypeQuery() *ast.Node {
// Make sure we perform ASI to prevent parsing the next line's type arguments as part of an instantiation expression
var typeArguments *ast.NodeList
if !p.hasPrecedingLineBreak() {
typeArguments = p.parseTypeArguments()
if p.token == ast.KindLessThanLessThanToken {
// `<<` may start type arguments whose first type is generic (`typeof f<<T>(x: T) => T>`), but it
// may also be a left shift following a type in an expression (`x as typeof y << 1`). Only treat it
// as type arguments if they parse without errors.
state := p.mark()
typeArguments = p.parseTypeArguments()
if len(p.diagnostics) != state.diagnosticsLen {
p.rewind(state)
typeArguments = nil
}
} else {
typeArguments = p.parseTypeArguments()
}
}
return p.finishNode(p.factory.NewTypeQueryNode(entityName, typeArguments), pos)
}
Expand Down
65 changes: 65 additions & 0 deletions tsc/testdata/baselines/reference/compiler/parseGenericArrowRatherThanLeftShift2.js
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@@ -0,0 +1,65 @@
//// [tests/cases/compiler/parseGenericArrowRatherThanLeftShift2.tsx] ////

//// [heritage.ts]
declare const f: <T>(x: T) => T;
declare function g(): typeof B;
declare class B<F> {}
interface I<F> {}
interface J<F> {}

class C1 implements I<<T>(x: T) => T> {}
class C2 extends B<<T>(x: T) => T> {}
const C3 = class extends g()<<T>(x: T) => T> {};
interface I2 extends J<<T>(x: T) => T> {}
type A1 = typeof f<<T>(x: T) => T>;

const e1 = f<<T>(x: T) => T>;
const e2 = f<<T>(x: T) => T>(f);

// `<<` is still a left shift in expressions.
declare let n: number;
const s1 = n << 2;
const s2 = n<<n;
const s3 = (n<<n) > n;

// `<<` after a type query in an expression is still a left shift.
declare const a: any;
const s4 = a as typeof n << 1;
const s5 = a satisfies typeof n << 1;

//// [jsx.tsx]
declare namespace JSX {
interface Element {}
interface IntrinsicElements {
div: { x?: number };
}
}
declare function Comp<P>(props: { value: P }): JSX.Element;

const j1 = <Comp<<T>(x: T) => T> value={f} />;
const j2 = <Comp<<T>(x: T) => T> value={f}></Comp>;
const j3 = <div x={n << 1} />;
const j4 = <div x={n<<n} />;


//// [heritage.js]
"use strict";
class C1 {
}
class C2 extends B {
}
const C3 = class extends g() {
};
const e1 = f;
const e2 = f(f);
const s1 = n << 2;
const s2 = n << n;
const s3 = (n << n) > n;
const s4 = a << 1;
const s5 = a << 1;
//// [jsx.jsx]
"use strict";
const j1 = <Comp value={f}/>;
const j2 = <Comp value={f}></Comp>;
const j3 = <div x={n << 1}/>;
const j4 = <div x={n << n}/>;
174 changes: 174 additions & 0 deletions tsc/testdata/baselines/reference/compiler/parseGenericArrowRatherThanLeftShift2.symbols
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@@ -0,0 +1,174 @@
//// [tests/cases/compiler/parseGenericArrowRatherThanLeftShift2.tsx] ////

=== heritage.ts ===
declare const f: <T>(x: T) => T;
>f : Symbol(f, Decl(heritage.ts, 0, 13))
>T : Symbol(T, Decl(heritage.ts, 0, 18))
>x : Symbol(x, Decl(heritage.ts, 0, 21))
>T : Symbol(T, Decl(heritage.ts, 0, 18))
>T : Symbol(T, Decl(heritage.ts, 0, 18))

declare function g(): typeof B;
>g : Symbol(g, Decl(heritage.ts, 0, 32))
>B : Symbol(B, Decl(heritage.ts, 1, 31))

declare class B<F> {}
>B : Symbol(B, Decl(heritage.ts, 1, 31))
>F : Symbol(F, Decl(heritage.ts, 2, 16))

interface I<F> {}
>I : Symbol(I, Decl(heritage.ts, 2, 21))
>F : Symbol(F, Decl(heritage.ts, 3, 12))

interface J<F> {}
>J : Symbol(J, Decl(heritage.ts, 3, 17))
>F : Symbol(F, Decl(heritage.ts, 4, 12))

class C1 implements I<<T>(x: T) => T> {}
>C1 : Symbol(C1, Decl(heritage.ts, 4, 17))
>I : Symbol(I, Decl(heritage.ts, 2, 21))
>T : Symbol(T, Decl(heritage.ts, 6, 23))
>x : Symbol(x, Decl(heritage.ts, 6, 26))
>T : Symbol(T, Decl(heritage.ts, 6, 23))
>T : Symbol(T, Decl(heritage.ts, 6, 23))

class C2 extends B<<T>(x: T) => T> {}
>C2 : Symbol(C2, Decl(heritage.ts, 6, 40))
>B : Symbol(B, Decl(heritage.ts, 1, 31))
>T : Symbol(T, Decl(heritage.ts, 7, 20))
>x : Symbol(x, Decl(heritage.ts, 7, 23))
>T : Symbol(T, Decl(heritage.ts, 7, 20))
>T : Symbol(T, Decl(heritage.ts, 7, 20))

const C3 = class extends g()<<T>(x: T) => T> {};
>C3 : Symbol(C3, Decl(heritage.ts, 8, 5))
>g : Symbol(g, Decl(heritage.ts, 0, 32))
>T : Symbol(T, Decl(heritage.ts, 8, 30))
>x : Symbol(x, Decl(heritage.ts, 8, 33))
>T : Symbol(T, Decl(heritage.ts, 8, 30))
>T : Symbol(T, Decl(heritage.ts, 8, 30))

interface I2 extends J<<T>(x: T) => T> {}
>I2 : Symbol(I2, Decl(heritage.ts, 8, 48))
>J : Symbol(J, Decl(heritage.ts, 3, 17))
>T : Symbol(T, Decl(heritage.ts, 9, 24))
>x : Symbol(x, Decl(heritage.ts, 9, 27))
>T : Symbol(T, Decl(heritage.ts, 9, 24))
>T : Symbol(T, Decl(heritage.ts, 9, 24))

type A1 = typeof f<<T>(x: T) => T>;
>A1 : Symbol(A1, Decl(heritage.ts, 9, 41))
>f : Symbol(f, Decl(heritage.ts, 0, 13))
>T : Symbol(T, Decl(heritage.ts, 10, 20))
>x : Symbol(x, Decl(heritage.ts, 10, 23))
>T : Symbol(T, Decl(heritage.ts, 10, 20))
>T : Symbol(T, Decl(heritage.ts, 10, 20))

const e1 = f<<T>(x: T) => T>;
>e1 : Symbol(e1, Decl(heritage.ts, 12, 5))
>f : Symbol(f, Decl(heritage.ts, 0, 13))
>T : Symbol(T, Decl(heritage.ts, 12, 14))
>x : Symbol(x, Decl(heritage.ts, 12, 17))
>T : Symbol(T, Decl(heritage.ts, 12, 14))
>T : Symbol(T, Decl(heritage.ts, 12, 14))

const e2 = f<<T>(x: T) => T>(f);
>e2 : Symbol(e2, Decl(heritage.ts, 13, 5))
>f : Symbol(f, Decl(heritage.ts, 0, 13))
>T : Symbol(T, Decl(heritage.ts, 13, 14))
>x : Symbol(x, Decl(heritage.ts, 13, 17))
>T : Symbol(T, Decl(heritage.ts, 13, 14))
>T : Symbol(T, Decl(heritage.ts, 13, 14))
>f : Symbol(f, Decl(heritage.ts, 0, 13))

// `<<` is still a left shift in expressions.
declare let n: number;
>n : Symbol(n, Decl(heritage.ts, 16, 11))

const s1 = n << 2;
>s1 : Symbol(s1, Decl(heritage.ts, 17, 5))
>n : Symbol(n, Decl(heritage.ts, 16, 11))

const s2 = n<<n;
>s2 : Symbol(s2, Decl(heritage.ts, 18, 5))
>n : Symbol(n, Decl(heritage.ts, 16, 11))
>n : Symbol(n, Decl(heritage.ts, 16, 11))

const s3 = (n<<n) > n;
>s3 : Symbol(s3, Decl(heritage.ts, 19, 5))
>n : Symbol(n, Decl(heritage.ts, 16, 11))
>n : Symbol(n, Decl(heritage.ts, 16, 11))
>n : Symbol(n, Decl(heritage.ts, 16, 11))

// `<<` after a type query in an expression is still a left shift.
declare const a: any;
>a : Symbol(a, Decl(heritage.ts, 22, 13))

const s4 = a as typeof n << 1;
>s4 : Symbol(s4, Decl(heritage.ts, 23, 5))
>a : Symbol(a, Decl(heritage.ts, 22, 13))
>n : Symbol(n, Decl(heritage.ts, 16, 11))

const s5 = a satisfies typeof n << 1;
>s5 : Symbol(s5, Decl(heritage.ts, 24, 5))
>a : Symbol(a, Decl(heritage.ts, 22, 13))
>n : Symbol(n, Decl(heritage.ts, 16, 11))

=== jsx.tsx ===
declare namespace JSX {
>JSX : Symbol(JSX, Decl(jsx.tsx, 0, 0))

interface Element {}
>Element : Symbol(Element, Decl(jsx.tsx, 0, 23))

interface IntrinsicElements {
>IntrinsicElements : Symbol(IntrinsicElements, Decl(jsx.tsx, 1, 24))

div: { x?: number };
>div : Symbol(IntrinsicElements.div, Decl(jsx.tsx, 2, 33))
>x : Symbol(x, Decl(jsx.tsx, 3, 14))
}
}
declare function Comp<P>(props: { value: P }): JSX.Element;
>Comp : Symbol(Comp, Decl(jsx.tsx, 5, 1))
>P : Symbol(P, Decl(jsx.tsx, 6, 22))
>props : Symbol(props, Decl(jsx.tsx, 6, 25))
>value : Symbol(value, Decl(jsx.tsx, 6, 33))
>P : Symbol(P, Decl(jsx.tsx, 6, 22))
>JSX : Symbol(JSX, Decl(jsx.tsx, 0, 0))
>Element : Symbol(JSX.Element, Decl(jsx.tsx, 0, 23))

const j1 = <Comp<<T>(x: T) => T> value={f} />;
>j1 : Symbol(j1, Decl(jsx.tsx, 8, 5))
>Comp : Symbol(Comp, Decl(jsx.tsx, 5, 1))
>T : Symbol(T, Decl(jsx.tsx, 8, 18))
>x : Symbol(x, Decl(jsx.tsx, 8, 21))
>T : Symbol(T, Decl(jsx.tsx, 8, 18))
>T : Symbol(T, Decl(jsx.tsx, 8, 18))
>value : Symbol(value, Decl(jsx.tsx, 8, 32))
>f : Symbol(f, Decl(heritage.ts, 0, 13))

const j2 = <Comp<<T>(x: T) => T> value={f}></Comp>;
>j2 : Symbol(j2, Decl(jsx.tsx, 9, 5))
>Comp : Symbol(Comp, Decl(jsx.tsx, 5, 1))
>T : Symbol(T, Decl(jsx.tsx, 9, 18))
>x : Symbol(x, Decl(jsx.tsx, 9, 21))
>T : Symbol(T, Decl(jsx.tsx, 9, 18))
>T : Symbol(T, Decl(jsx.tsx, 9, 18))
>value : Symbol(value, Decl(jsx.tsx, 9, 32))
>f : Symbol(f, Decl(heritage.ts, 0, 13))
>Comp : Symbol(Comp, Decl(jsx.tsx, 5, 1))

const j3 = <div x={n << 1} />;
>j3 : Symbol(j3, Decl(jsx.tsx, 10, 5))
>div : Symbol(JSX.IntrinsicElements.div, Decl(jsx.tsx, 2, 33))
>x : Symbol(x, Decl(jsx.tsx, 10, 15))
>n : Symbol(n, Decl(heritage.ts, 16, 11))

const j4 = <div x={n<<n} />;
>j4 : Symbol(j4, Decl(jsx.tsx, 11, 5))
>div : Symbol(JSX.IntrinsicElements.div, Decl(jsx.tsx, 2, 33))
>x : Symbol(x, Decl(jsx.tsx, 11, 15))
>n : Symbol(n, Decl(heritage.ts, 16, 11))
>n : Symbol(n, Decl(heritage.ts, 16, 11))

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