Clear and concise description of the problem

I'd love to be able to get information about the callsite of the macro inside of the macro. At a basic level, this would be something like { filepath: string, lineNumber: number }, but I imagine could include additional information such as surrounding AST.

An example of what this would be useful for is to inject callsite information automatically into OpenTelemtetry without having to do the expensive and inaccurate (in the case of bundling) operation of retrieving a stacktrace at runtime.

Motivating examples:

// src/myfile.ts
import { $autoFunctionLabel, $autoCallsite, $autoLine, $autoSmartAssertCondition } from 'my-lib' with { type: 'macro' }

class MyClass {
  myFunction() {
    const span = tracer.startSpan($autoFunctionLabel())
    span.setAttribute("callsite", $autoCallsite())

    const x = 5;
    const y = 10;

    assert(x == y, `Assertion failed! Context: "${$autoLine()}"`)
    // a more intelligent variant
    assert(x == y, `Assertion failed! Condition: "${$autoSmartAssertCondition()}"`)
  }
}

// transforms into

class MyClass {
  myFunction() {
    const span = tracer.startSpan("MyClass.myFunction")
    span.setAttribute("callsite", "src/myfile.ts:42")

    const x = 5;
    const y = 10;

    assert(x == y, `Assertion failed! Context: "assert(x == y, \`Assertion failed! Context: \${$autoLine()}\`)"`)
    // a more intelligent variant
    assert(x == y, `Assertion failed! Condition: "x == y"`)
  }
}

Suggested solution

Expose callsite information in the MacroContext.

• absolute file path to the file on disk being transformed
• line number
• line contents
• AST and a pointer to the callsite or something?

Alternative

N/A

Additional context

N/A

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.