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In JS, type parameter from @type JSDoc tag doesn't get instantiated #25618

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ajafff opened this issue Jul 12, 2018 · 0 comments · Fixed by #26694
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In JS, type parameter from @type JSDoc tag doesn't get instantiated #25618

ajafff opened this issue Jul 12, 2018 · 0 comments · Fixed by #26694
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@sandersn
Labels
Bug A bug in TypeScript checkJs Relates to checking JavaScript using TypeScript Fixed A PR has been merged for this issue
Milestone
TypeScript 3.1

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@ajafff
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ajafff commented Jul 12, 2018

TypeScript Version: 3.0.0-dev.20180712

Search Terms:

Code

// @checkJs: true
// @allowJs: true

// @filename: test.js

/** @type {<T>(param?: T) => T | undefined} */
function typed(param) {
    return param;
}
typed(1);

Expected behavior:

Either param doesn't get it's type from the @type tag or the type parameter T applies to the function.

Actual behavior:

Argument of type '1' is not assignable to parameter of type 'T | undefined'.

Playground Link: not possible

Related Issues: #25525
@mhegazy mhegazy added this to the TypeScript 3.1 milestone Jul 12, 2018
@mhegazy mhegazy added Bug A bug in TypeScript Salsa checkJs Relates to checking JavaScript using TypeScript labels Jul 12, 2018
@sandersn sandersn changed the title In JS, function declaration should use type parameter of @type JSDoc tag In JS, type parameter of @type JSDoc tag doesn't get instantiated Jul 12, 2018
@sandersn sandersn changed the title In JS, type parameter of @type JSDoc tag doesn't get instantiated In JS, type parameter from @type JSDoc tag doesn't get instantiated Jul 12, 2018
@sandersn sandersn mentioned this issue Aug 23, 2018
Closed
@sandersn sandersn added the Fixed A PR has been merged for this issue label Aug 27, 2018
sandersn added a commit that referenced this issue Aug 27, 2018
@sandersn
Get [type] parameter types from @type tag
ed8949e 
Previously only the return type was used in cases like this:

```js
/** @type {<T>(param?: T) => T | undefined} */
function g(param) {
  return param;
}
```

Now the type parameters from the type tag are used, and the compiler
gets the type of the parameter by using the position in the signature of
the type tag.

Fixes #25618
@sandersn sandersn mentioned this issue Aug 27, 2018
Merged
sandersn added a commit that referenced this issue Aug 27, 2018
@sandersn
Get [type] parameter types from @type tag (#26694)
a2e4a28 
* Get [type] parameter types from @type tag

Previously only the return type was used in cases like this:

```js
/** @type {<T>(param?: T) => T | undefined} */
function g(param) {
  return param;
}
```

Now the type parameters from the type tag are used, and the compiler
gets the type of the parameter by using the position in the signature of
the type tag.

Fixes #25618

* Fix split ifs according to PR comments
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@sandersn sandersn

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Bug A bug in TypeScript checkJs Relates to checking JavaScript using TypeScript Fixed A PR has been merged for this issue
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TypeScript 3.1
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Get [type] parameter types from @type tag microsoft/TypeScript
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@sandersn @mhegazy @ajafff