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gccgo: bad "incompatible types" error when comparing untyped expressions #33306

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mdempsky opened this issue Jul 26, 2019 · 0 comments

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@mdempsky
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commented Jul 26, 2019

gccgo incorrectly reports error: incompatible types in binary expression for this test program:

package main

func main() {
        var v uint = 32
        println(1 << v == '\002' << v)
}

The Go spec says:

If the left operand of a non-constant shift expression is an untyped constant, it is first implicitly converted to the type it would assume if the shift expression were replaced by its left operand alone.

So 1 and '\002' should take on the types that they would in the comparison 1 == '\002', which is rune/int32.

For comparison, the program prints true when compiled with cmd/compile, and it type checks with go/types.

/cc @ianlancetaylor

@mdempsky mdempsky added this to the Gccgo milestone Jul 26, 2019

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