Track origin's occurrences

[turbolent]

Description

Record occurrences in origins, so that it is possible to get all occurrences from one occurrence.

For example, in the following program:

struct Counter {
    var n: Int

    init() {
        self.n = 0
    }

    fun inc() {
        self.n = self.n + 1
    }
}

It is possible to get from one of the occurrences of field n in functions inc to the origin, the field declaration on line 2, and from there get all occurrences (the one in the initializer, and the other two in the inc function.

Also:

• Fix the origin range for field declarations
• Add a function to get all occurrences for a position (multiple checker passes (re)declare occurrences)

---

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels