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Restore import defer = parsing #61837

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5 changes: 4 additions & 1 deletion src/compiler/parser.ts
Original file line number Diff line number Diff line change
Expand Up @@ -8392,7 +8392,10 @@ namespace Parser {
phaseModifier = SyntaxKind.TypeKeyword;
identifier = isIdentifier() ? parseIdentifier() : undefined;
}
else if (identifier?.escapedText === "defer" && token() !== SyntaxKind.FromKeyword) {
else if (
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@jakebailey jakebailey Jun 9, 2025

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Why isn't this just the same as what's done for type above? You can't mix type and defer, so I would have expected both to parse in the same fashion.

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The difference is that the type parsing considers type as a modifier in import type foo =, while the defer parsing doesn't in import defer foo =.

Do you prefer if I unify the path, but then add a "nice" error for import defer foo = rather than just complaining about the unexpected foo/=?

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Daniel pointed out there's a difference between them in other ways like import type foo, { bar } from "..." is not legal as it's ambiguous whether or not bar is type or not. So, all good.

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@nicolo-ribaudo nicolo-ribaudo Jun 9, 2025

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Well technically we could still unify parsing for them and report that type case as an "early error" while still building the proper AST.

(I'm happy to both keep the code as-is or to update it)

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After thinking more, technically neither allow named bindings or defaults. I think this is okay as-is. I'll make a second PR to add more tests.

identifier?.escapedText === "defer" &&
(token() === SyntaxKind.FromKeyword ? !lookAhead(nextTokenIsStringLiteral) : token() !== SyntaxKind.CommaToken && token() !== SyntaxKind.EqualsToken)
) {
phaseModifier = SyntaxKind.DeferKeyword;
identifier = isIdentifier() ? parseIdentifier() : undefined;
}
Expand Down
13 changes: 13 additions & 0 deletions tests/baselines/reference/importBindingDefer.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
//// [tests/cases/conformance/importDefer/importBindingDefer.ts] ////

//// [a.ts]
export default 2;

//// [b.ts]
import defer from "./a.js";


//// [a.js]
export default 2;
//// [b.js]
export {};
10 changes: 10 additions & 0 deletions tests/baselines/reference/importBindingDefer.symbols
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
//// [tests/cases/conformance/importDefer/importBindingDefer.ts] ////

=== a.ts ===

export default 2;

=== b.ts ===
import defer from "./a.js";
>defer : Symbol(defer, Decl(b.ts, 0, 6))

11 changes: 11 additions & 0 deletions tests/baselines/reference/importBindingDefer.types
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
//// [tests/cases/conformance/importDefer/importBindingDefer.ts] ////

=== a.ts ===

export default 2;

=== b.ts ===
import defer from "./a.js";
>defer : 2
> : ^

13 changes: 13 additions & 0 deletions tests/baselines/reference/importBindingDefer2.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
//// [tests/cases/conformance/importDefer/importBindingDefer2.ts] ////

//// [a.ts]
export default 2;

//// [b.ts]
import defer, {} from "./a.js";


//// [a.js]
export default 2;
//// [b.js]
export {};
10 changes: 10 additions & 0 deletions tests/baselines/reference/importBindingDefer2.symbols
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
//// [tests/cases/conformance/importDefer/importBindingDefer2.ts] ////

=== a.ts ===

export default 2;

=== b.ts ===
import defer, {} from "./a.js";
>defer : Symbol(defer, Decl(b.ts, 0, 6))

11 changes: 11 additions & 0 deletions tests/baselines/reference/importBindingDefer2.types
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
//// [tests/cases/conformance/importDefer/importBindingDefer2.ts] ////

=== a.ts ===

export default 2;

=== b.ts ===
import defer, {} from "./a.js";
>defer : 2
> : ^

11 changes: 11 additions & 0 deletions tests/baselines/reference/importDeferFromInvalid.errors.txt
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
b.ts(1,8): error TS18058: Default imports are not allowed in a deferred import.


==== a.ts (0 errors) ====
export default 2;

==== b.ts (1 errors) ====
import defer from from "./a.js";
~~~~~~~~~~
!!! error TS18058: Default imports are not allowed in a deferred import.

13 changes: 13 additions & 0 deletions tests/baselines/reference/importDeferFromInvalid.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
//// [tests/cases/conformance/importDefer/importDeferFromInvalid.ts] ////

//// [a.ts]
export default 2;

//// [b.ts]
import defer from from "./a.js";


//// [a.js]
export default 2;
//// [b.js]
export {};
10 changes: 10 additions & 0 deletions tests/baselines/reference/importDeferFromInvalid.symbols
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
//// [tests/cases/conformance/importDefer/importDeferFromInvalid.ts] ////

=== a.ts ===

export default 2;

=== b.ts ===
import defer from from "./a.js";
>from : Symbol(from, Decl(b.ts, 0, 6))

11 changes: 11 additions & 0 deletions tests/baselines/reference/importDeferFromInvalid.types
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
//// [tests/cases/conformance/importDefer/importDeferFromInvalid.ts] ////

=== a.ts ===

export default 2;

=== b.ts ===
import defer from from "./a.js";
>from : 2
> : ^

15 changes: 15 additions & 0 deletions tests/baselines/reference/importEqualsBindingDefer.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
//// [tests/cases/conformance/importDefer/importEqualsBindingDefer.ts] ////

//// [a.ts]
export = 2;

//// [b.ts]
import defer = require("./a");


//// [a.js]
"use strict";
module.exports = 2;
//// [b.js]
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
10 changes: 10 additions & 0 deletions tests/baselines/reference/importEqualsBindingDefer.symbols
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
//// [tests/cases/conformance/importDefer/importEqualsBindingDefer.ts] ////

=== b.ts ===
import defer = require("./a");
>defer : Symbol(defer, Decl(b.ts, 0, 0))

=== a.ts ===

export = 2;

11 changes: 11 additions & 0 deletions tests/baselines/reference/importEqualsBindingDefer.types
Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
//// [tests/cases/conformance/importDefer/importEqualsBindingDefer.ts] ////

=== b.ts ===
import defer = require("./a");
>defer : 2
> : ^

=== a.ts ===

export = 2;

8 changes: 8 additions & 0 deletions tests/cases/conformance/importDefer/importBindingDefer.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
// @module: esnext
// @target: es2020

// @filename: a.ts
export default 2;

// @filename: b.ts
import defer from "./a.js";
8 changes: 8 additions & 0 deletions tests/cases/conformance/importDefer/importBindingDefer2.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
// @module: esnext
// @target: es2020

// @filename: a.ts
export default 2;

// @filename: b.ts
import defer, {} from "./a.js";
8 changes: 8 additions & 0 deletions tests/cases/conformance/importDefer/importDeferFromInvalid.ts
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
// @module: esnext
// @target: es2020

// @filename: a.ts
export default 2;

// @filename: b.ts
import defer from from "./a.js";
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
// @module: commonjs
// @target: es2020

// @filename: a.ts
export = 2;

// @filename: b.ts
import defer = require("./a");