Order of evaluation for child nodes is not specified.

[Teemperor]

It seems the spec is missing how child nodes are evaluation. Problems that could arise through that are:

1 . Child nodes with side effects would make the program behave differently on different platforms like in:

(set_local $x (i32.const 8))
(int32.div (get_local $x) (set_local $x (i32.const 4))

div could either return 1 or 0 in this case.

2 . Unnecessary locals to clarify the order of evaluation. Example from above with clear order but unnecessary locals:

(set_local $x (i32.const 8))
(set_local $right (set_local $x (i32.const 4))
(int32.div (get_local $x) (get_local $right)

[AndrewScheidecker]

I thought I saw it define evaluation to occur in lexical order somewhere, but I can't find the reference now. Maybe it got lost in the shuffle?

[pjuftring]

TestingTodo says, that operands have to be evaluated from left to right.

[jcbeyler]

Tests for this already exist by the way:
WebAssembly/spec#119

Not saying this should not be stated :); just saying we have tests for it now

[lukewagner]

The intention is indeed for evaluation order to be deterministic, in the order defined by the spec. I agree it would be good to note this explicitly in AstSemantics.md, though.

[lukewagner]

Merged #401.