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Fix top-level await parsing (#38483) #38518

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Fix top-level await parsing (#38483) #38518

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9 changes: 8 additions & 1 deletion src/compiler/parser.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4150,8 +4150,15 @@ namespace ts {
return true;
}

// This handles cases like `await (async () => {})()`
// One drawback of this implementation is that we cannot use this form in top-level
// if there is an "await" identifier as we cannot differentiate this two cases
const isCallLike = () => {
return (nextToken() === SyntaxKind.OpenParenToken && !identifiers.has("await")) && !scanner.hasPrecedingLineBreak();
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The problem with this approach is function hoisting. Your example has this:

function await(fn) {
  return () => {};
}
await (async () => {})(); // equivalent to: await((async () => {})())

However, it should also fail in this case:

await (async () => {})(); // equivalent to: await((async () => {})())
function await(fn) {
  return () => {};
}

I don't think this is the correct solution to the underlying problem.

};

// here we are using similar heuristics as 'isYieldExpression'
return lookAhead(nextTokenIsIdentifierOrKeywordOrLiteralOnSameLine);
return lookAhead(isCallLike) || lookAhead(nextTokenIsIdentifierOrKeywordOrLiteralOnSameLine);
}

return false;
Expand Down
8 changes: 6 additions & 2 deletions tests/baselines/reference/topLevelAwait(module=esnext,target=es2015).errors.txt
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@@ -1,9 +1,13 @@
tests/cases/conformance/externalModules/topLevelAwait.ts(2,1): error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.
tests/cases/conformance/externalModules/topLevelAwait.ts(4,1): error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.


==== tests/cases/conformance/externalModules/topLevelAwait.ts (1 errors) ====
==== tests/cases/conformance/externalModules/topLevelAwait.ts (2 errors) ====
export const x = 1;
await x;
~~~~~
!!! error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.


await (async () => {})();
~~~~~
!!! error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.
13 changes: 12 additions & 1 deletion tests/baselines/reference/topLevelAwait(module=esnext,target=es2015).js
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@@ -1,8 +1,19 @@
//// [topLevelAwait.ts]
export const x = 1;
await x;


await (async () => {})();

//// [topLevelAwait.js]
var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
return new (P || (P = Promise))(function (resolve, reject) {
function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
step((generator = generator.apply(thisArg, _arguments || [])).next());
});
};
export const x = 1;
await x;
await (() => __awaiter(void 0, void 0, void 0, function* () { }))();
1 change: 1 addition & 0 deletions tests/baselines/reference/topLevelAwait(module=esnext,target=es2015).symbols
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Expand Up @@ -5,3 +5,4 @@ export const x = 1;
await x;
>x : Symbol(x, Decl(topLevelAwait.ts, 0, 12))

await (async () => {})();
6 changes: 6 additions & 0 deletions tests/baselines/reference/topLevelAwait(module=esnext,target=es2015).types
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Expand Up @@ -7,3 +7,9 @@ await x;
>await x : 1
>x : 1

await (async () => {})();
>await (async () => {})() : void
>(async () => {})() : Promise<void>
>(async () => {}) : () => Promise<void>
>async () => {} : () => Promise<void>

4 changes: 3 additions & 1 deletion tests/baselines/reference/topLevelAwait(module=esnext,target=es2017).js
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@@ -1,8 +1,10 @@
//// [topLevelAwait.ts]
export const x = 1;
await x;


await (async () => {})();

//// [topLevelAwait.js]
export const x = 1;
await x;
await (async () => { })();
1 change: 1 addition & 0 deletions tests/baselines/reference/topLevelAwait(module=esnext,target=es2017).symbols
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Original file line number Diff line number Diff line change
Expand Up @@ -5,3 +5,4 @@ export const x = 1;
await x;
>x : Symbol(x, Decl(topLevelAwait.ts, 0, 12))

await (async () => {})();
6 changes: 6 additions & 0 deletions tests/baselines/reference/topLevelAwait(module=esnext,target=es2017).types
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Original file line number Diff line number Diff line change
Expand Up @@ -7,3 +7,9 @@ await x;
>await x : 1
>x : 1

await (async () => {})();
>await (async () => {})() : void
>(async () => {})() : Promise<void>
>(async () => {}) : () => Promise<void>
>async () => {} : () => Promise<void>

8 changes: 6 additions & 2 deletions tests/baselines/reference/topLevelAwait(module=system,target=es2015).errors.txt
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Original file line number Diff line number Diff line change
@@ -1,9 +1,13 @@
tests/cases/conformance/externalModules/topLevelAwait.ts(2,1): error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.
tests/cases/conformance/externalModules/topLevelAwait.ts(4,1): error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.


==== tests/cases/conformance/externalModules/topLevelAwait.ts (1 errors) ====
==== tests/cases/conformance/externalModules/topLevelAwait.ts (2 errors) ====
export const x = 1;
await x;
~~~~~
!!! error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.


await (async () => {})();
~~~~~
!!! error TS1378: Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.
13 changes: 12 additions & 1 deletion tests/baselines/reference/topLevelAwait(module=system,target=es2015).js
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@@ -1,18 +1,29 @@
//// [topLevelAwait.ts]
export const x = 1;
await x;


await (async () => {})();

//// [topLevelAwait.js]
System.register([], function (exports_1, context_1) {
"use strict";
var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
return new (P || (P = Promise))(function (resolve, reject) {
function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
step((generator = generator.apply(thisArg, _arguments || [])).next());
});
};
var x;
var __moduleName = context_1 && context_1.id;
return {
setters: [],
execute: async function () {
exports_1("x", x = 1);
await x;
await (() => __awaiter(void 0, void 0, void 0, function* () { }))();
}
};
});
1 change: 1 addition & 0 deletions tests/baselines/reference/topLevelAwait(module=system,target=es2015).symbols
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Original file line number Diff line number Diff line change
Expand Up @@ -5,3 +5,4 @@ export const x = 1;
await x;
>x : Symbol(x, Decl(topLevelAwait.ts, 0, 12))

await (async () => {})();
6 changes: 6 additions & 0 deletions tests/baselines/reference/topLevelAwait(module=system,target=es2015).types
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Original file line number Diff line number Diff line change
Expand Up @@ -7,3 +7,9 @@ await x;
>await x : 1
>x : 1

await (async () => {})();
>await (async () => {})() : void
>(async () => {})() : Promise<void>
>(async () => {}) : () => Promise<void>
>async () => {} : () => Promise<void>

4 changes: 3 additions & 1 deletion tests/baselines/reference/topLevelAwait(module=system,target=es2017).js
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@@ -1,7 +1,8 @@
//// [topLevelAwait.ts]
export const x = 1;
await x;


await (async () => {})();

//// [topLevelAwait.js]
System.register([], function (exports_1, context_1) {
Expand All @@ -13,6 +14,7 @@ System.register([], function (exports_1, context_1) {
execute: async function () {
exports_1("x", x = 1);
await x;
await (async () => { })();
}
};
});
1 change: 1 addition & 0 deletions tests/baselines/reference/topLevelAwait(module=system,target=es2017).symbols
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Original file line number Diff line number Diff line change
Expand Up @@ -5,3 +5,4 @@ export const x = 1;
await x;
>x : Symbol(x, Decl(topLevelAwait.ts, 0, 12))

await (async () => {})();
6 changes: 6 additions & 0 deletions tests/baselines/reference/topLevelAwait(module=system,target=es2017).types
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Original file line number Diff line number Diff line change
Expand Up @@ -7,3 +7,9 @@ await x;
>await x : 1
>x : 1

await (async () => {})();
>await (async () => {})() : void
>(async () => {})() : Promise<void>
>(async () => {}) : () => Promise<void>
>async () => {} : () => Promise<void>

2 changes: 2 additions & 0 deletions tests/cases/conformance/externalModules/topLevelAwait.ts
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Expand Up @@ -2,3 +2,5 @@
// @module: esnext,system
export const x = 1;
await x;

await (async () => {})();