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x/tools/go/ssa: bad order of evaluation with slice expressions #52142

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mdempsky opened this issue Apr 4, 2022 · 1 comment
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x/tools/go/ssa: bad order of evaluation with slice expressions #52142

mdempsky opened this issue Apr 4, 2022 · 1 comment
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. Tools This label describes issues relating to any tools in the x/tools repository.
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@mdempsky
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mdempsky commented Apr 4, 2022

This function:

func F(s []int, f, g func() int) []int { return s[f():g()] }

should invoke f() before g(), because it's lexically to the left. But when compiled with x/tools/go/ssa, it gives the opposite order:

func F(s []int, f func() int, g func() int) []int:
0:                                                                entry P:0 S:0
	t0 = g()                                                            int
	t1 = f()                                                            int
	t2 = slice s[t1:t0]                                               []int
	return t2

https://go.dev/play/p/aY22d2R-3Zw

I think this is simply because the ast.SliceExpr case in builder.expr visits e.High before e.Low.

/cc @timothy-king @zpavlinovic @findleyr
@mdempsky mdempsky added the NeedsFix The path to resolution is known, but the work has not been done. label Apr 4, 2022
@gopherbot gopherbot added the Tools This label describes issues relating to any tools in the x/tools repository. label Apr 4, 2022
@gopherbot gopherbot added this to the Unreleased milestone Apr 4, 2022
mdempsky added a commit to despiteallobjections/amigo that referenced this issue Apr 4, 2022
@mdempsky
amigo/types: add reference to Go issue tracker
dbebb34 
Updates golang/go#52142.
@timothy-king timothy-king self-assigned this Apr 4, 2022
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Change https://go.dev/cl/398057 mentions this issue: go/ssa: emit Low expression before High in *ast.Slice

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