microsoft / microsoft/TypeScript-TmLanguage
Comparison operators ("<", ">") incorrectly interpreted as type parameters
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- Dominant language
- TypeScript
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Description
TS and JS Grammar Extension version: 0.0.55 / latest
Code
// Contrived because of simplification
let a = 7
let b = {}
if (a < (b as {c: number}).c || a > (b as {c: number}).c) {
}
If statement parsing:
if [keyword.control.conditional.ts, source.ts]
( [meta.brace.round.ts, source.ts]
a [entity.name.function.ts, meta.function-call.ts, source.ts]
< [punctuation.definition.typeparameters.begin.ts, meta.type.parameters.ts, source.ts]
( [meta.brace.round.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
b [entity.name.type.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
as [entity.name.type.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
{ [punctuation.definition.block.ts, meta.object.type.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
c [variable.object.property.ts, meta.definition.property.ts, meta.field.declaration.ts, meta.object.type.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
: [meta.type.annotation.ts, meta.field.declaration.ts, meta.object.type.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
number [support.type.primitive.ts, meta.type.annotation.ts, meta.field.declaration.ts, meta.object.type.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
} [punctuation.definition.block.ts, meta.object.type.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
) [meta.brace.round.ts, meta.type.paren.cover.ts, meta.type.parameters.ts, source.ts]
. [meta.type.parameters.ts, source.ts]
c [entity.name.type.ts, meta.type.parameters.ts, source.ts]
| [keyword.operator.type.ts, meta.type.parameters.ts, source.ts]
| [keyword.operator.type.ts, meta.type.parameters.ts, source.ts]
a [entity.name.type.ts, meta.type.parameters.ts, source.ts]
> [punctuation.definition.typeparameters.begin.ts, meta.type.parameters.ts, source.ts]
(rest is normal)
So like:
if ( a<type>(parameters).c ) {}
Example in vscode:

Actual code:

Contributor guide
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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 with the TypeScript and JavaScript Grammar Extension and reproduce the reported snippet in VS Code using the syntax scopes shown in the issue. Trace how the comparison operators are classified in the grammar; done means < and > remain comparison operators while the surrounding type assertion and property access receive normal highlighting.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- typescript
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 48/100