microsoft / microsoft/TypeScript
JavaScript: default parameter causes type to be incorrectly inferred
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Domain: JavaScript
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Description
From https://github.com/Microsoft/vscode/issues/62013
TypeScript Version: 3.2.0-dev.20181027
Search Terms:
Code
For the javascript:
var SomeObject = {
SomeFunction: function (SomeInput) {
return SomeInput * 2;
},
SomeOtherFunction: function (SomeOtherInput, SomeOptionalInput = SomeObject.SomeFunction(2)) {
return SomeOtherInput * SomeOptionalInput;
}
};
SomeObject
Hover over SomeObject
Bug:
Type is any. If the default parameter is removed then the type is correct
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the hover result for SomeObject with TypeScript 3.2.0-dev.20181027, then compare it with the version where the default parameter is removed. The issue is done when the shown type is no longer any while preserving the default-parameter behavior; no source file or regression test is named in the report.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, typescript
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100