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cmd/compile: failure to diagnose invalid conversion to complex64 #11590

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dvyukov opened this issue Jul 4, 2015 · 5 comments
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cmd/compile: failure to diagnose invalid conversion to complex64 #11590

dvyukov opened this issue Jul 4, 2015 · 5 comments
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@dvyukov
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dvyukov commented Jul 4, 2015

gc successfully compiles the following program:

package a
var a = complex64(6)/774516156475830989403545856475830078125

while both gccgo and go/types reject it with:

error: complex real part overflow
774516156475830989403545856475830078125 (untyped int constant) overflows complex64

go version devel +40a1516 Fri Jul 3 03:08:40 2015 +0000 linux/amd64

@dvyukov
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dvyukov commented Jul 4, 2015

@griesemer

@griesemer
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I don't believe this is a gc bug. First of all, the conversion is not illegal - an untyped int constant can be converted into a complex value. The complaints are about overflow. But the value 774516156475830989403545856475830078125 is converted into a float64 w/o problem:

package a
var x float64 = 774516156475830989403545856475830078125

Making this a go/types bug.

@griesemer griesemer changed the title cmd/compile: does illegal int->complex conversion go/types: invalid error message for valid conversion to complex64 Jul 4, 2015
@griesemer griesemer assigned griesemer and unassigned rsc Jul 4, 2015
@griesemer
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Never mind - my bad! It's complex64 - not complex128! (I hate these names).

Indeed, "var _ float32 = 774516156475830989403545856475830078125" is not valid because the number is too large for any float32, and thus too large for any complex64 component.

gc should not accept this. Changing back to gc bug. Sorry.

@griesemer griesemer changed the title go/types: invalid error message for valid conversion to complex64 cmd/compile: invalid error message for valid conversion to complex64 Jul 9, 2015
@griesemer griesemer assigned rsc and unassigned griesemer Jul 9, 2015
@ianlancetaylor ianlancetaylor added this to the Go1.6 milestone Jul 10, 2015
@rsc
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rsc commented Nov 4, 2015

CL forthcoming.

@rsc rsc changed the title cmd/compile: invalid error message for valid conversion to complex64 cmd/compile: failure to diagnose invalid conversion to complex64 Nov 4, 2015
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CL https://golang.org/cl/16920 mentions this issue.

@rsc rsc closed this as completed in 2c11164 Nov 16, 2015
@golang golang locked and limited conversation to collaborators Nov 16, 2016
@rsc rsc removed their assignment Jun 23, 2022
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