Issue #20571 has been updated by jeremyevans0 (Jeremy Evans). I looked into this and was able to determine the underlying cause (currently on line 7844 of `compile.c`): ```c ADD_INSN(cond_seq, line_node, pop); /* discard cached #deconstruct value */ ``` Commenting that out fixes the example, though it causes overflow elsewhere. Most likely the `pop` instruction needs to be conditional, or we are missing a `dup` instruction somewhere. ---------------------------------------- Bug #20571: Compile error on for loop https://bugs.ruby-lang.org/issues/20571#change-109260 * Author: kddnewton (Kevin Newton) * Status: Open * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- ```ruby for _ in 1.5 or _ in [] end ``` raises a compile error for the current compiler only with ``` -- raw disasm-------- trace: 1 <L000> [sp: 0, unremovable: 1, refcnt: 1] 0000 putobject 1.5 ( 1) 0002 jump <L002> ( 1) <L006> [sp: 1, unremovable: 1, refcnt: 1] <L004> [sp: 1, unremovable: 0, refcnt: 0] 0004 pop ( 1) * 0005 pop ( 1) 0006 putobject false ( 1) <L002> [sp: 1, unremovable: 0, refcnt: 1] 0008 send <calldata:each, 0>, nil ( 1) <L001> [sp: -1, unremovable: 0, refcnt: 2] 0011 leave ( 1) --------------------- test.rb:1: argument stack underflow (-1) test.rb: compile error (SyntaxError) ``` -- https://bugs.ruby-lang.org/