Scope break values to loop bodies - #501

Summary

A break inside a while nested in an Array#each block is currently connected to the block's break vertex. For foo(flag), TypeProf infers (:b | Array[Integer]), as if each could return the loop's break value.

This is not an infinite loop: when flag is truthy, the body breaks immediately; otherwise, the while exits without entering the body. Array#each should therefore retain its Array[Integer] return type.

Give each loop body its own break vertex and restore the enclosing vertex after analysis so a loop-local break cannot escape the surrounding block.

Test

Ran the focused scenario set: break_in_loop.rb, break.rb, break2.rb, and loop.rb (4 scenarios, 9 assertions).