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Gather multiple contexts

A gather context asserts that every one of its child contexts holds at the marked instruction. It is the tool for composing multiple context facts that cannot coexist as sibling keys on a single object.

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When to use gather​

The context schema is open: a single context object may carry any number of discriminator keys together — code, variables, invoke, return, transform, and so on all compose as siblings on the same object. Prefer the flat form when it works.

Reach for gather only when two or more facts would collide on the same key. The canonical cases are:

  • Multiple frames — an instruction that maps simultaneously to an IR step and a source step needs one entry per frame, each with its own code range.
  • Multiple variables blocks — when separate pipeline passes each contribute variable information (e.g., one names the variable, the other supplies its pointer), each set lives in its own context.

If every child context uses a different discriminator key, a gather can be collapsed into a single flat object with the same meaning — and that flat form is the preferred style.