Calls.returns_proof: def of bolt@1.27.0.0
Import: import bolt@1.27.0.0/src/rules/calls.bend as Calls
Lines 264-275 of bolt@1.27.0.0/src/rules/calls.bend: https://jend.leeeet.dev/read.txt?path=bolt@1.27.0.0/src/rules/calls.bend&start_line=264&end_line=275

import Base
import bolt@1.27.0.0/src/syntax/tree.bend as Tree
import bolt@1.27.0.0/src/lazy/lazy.bend as Lazy

# does the signature return a proof, `-> {a == b : T}`?
def returns_proof(sig: Tree.Node) -> Bool:
  match sig:
    case Tree.NCons{h, +rest}:
      match rest:
        case Tree.NCons{+g, r2}:
          Lazy.either(Bool, kind.leaf(~kind.arrow, h), _u => returns_proof.or(Tree.opens(g, "{"), returns_proof(r2)),
            _v => returns_proof(rest))
        case _r:
          returns_proof(rest)
    case other:
      False{}

Uses (7):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/lazy/lazy.bend&name=either
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/rules/calls.bend&name=kind.arrow
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/rules/calls.bend&name=kind.leaf
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/rules/calls.bend&name=returns_proof.or
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/syntax/tree.bend&name=Node
  https://jend.leeeet.dev/definition.txt?path=bolt@1.27.0.0/src/syntax/tree.bend&name=opens