Gracefully handle template literal properties in the parser · Microsoft/TypeScript#1057

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Domain: Error MessagesEffort: ModerateExperience EnhancementHelp Wanted

Description

var x = {
    a: "Hello"
    `b`: 123
}

Right now, the parser encounters the template string, decides it should bail out of object literal parsing, and we more or less recover thinking we have something like the following:

var x = ({ a: "Hello" } `b`) : 123 }

So we'll report an error on what we think is:

{ a: "Hello" } `b`

On the syntactic layer under ES5 mode, we'll say tagged templates are not supported unless in ES6.
On the semantic layer, we'll say { a: "Hello" } is not invokable.

Contributor guide

Tech stack: typescript
Domain: backendtooling
Issue type: bug
Difficulty: 4
Estimated time: 1-2 days
Activity status: stale
Clarity: mostly clear
Prerequisites: Understanding of TypeScript's parserFamiliarity with object literal parsing
Newbie friendliness: 20
Research direction: Investigate the parser (likely in `src/compiler/parser.ts`) to understand how object literal properties are parsed and how template literals are treated. The issue describes that encountering a template literal in an object literal causes the parser to bail out incorrectly. Look for the code that handles property names and template literals. Consider adding a check to gracefully handle template literal properties by either parsing them as computed property names or generating a proper error message. Analyze the token stream to differentiate between a tagged template and a property template literal.