Unified: More work on AST and Swift mappings by asgerf · Pull Request #21962 · github/codeql

After a {expr} or {..expr} placeholder, an optional chain of
.<builtin>() calls may follow. Currently the only builtin is:

  .map(param -> template)

which applies the template to each element of the iterable and
collects the resulting node IDs. A chain auto-splices into the
enclosing field/child position.

Example:
  path: {parts}.map(p -> (identifier #{p}))

The framework is extensible: additional builtins can be added by
matching on the method name in parse_chain_suffix.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

A left fold over an iterable where the first element seeds the accumulator:
- first -> init  : converts the first element to the initial accumulator
- acc, elem -> fold : fold step; acc = current accumulator, elem = next element
- Empty iterable produces nothing (0-element splice)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Ensure the full wildcard _ supports quantifiers
- Also rewrite unnamed nodes in one-shot phases

When a field pattern has a bare capture with no preceding pattern
atom (i.e. `foo: @bar`), implicitly use a true wildcard (`_`,
match_unnamed: true) as the node pattern, making it equivalent to
`foo: _ @bar`.

This is a convenience shorthand: in practice every `field: _ @cap`
in the Swift rules can now be written more concisely as `field: @cap`.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>