cmd/gc: failure to detect set but not used variable captured by anon func

[davecheney]

For this function

package main

func f(fn func() error) error {
        return fn()
}

func main() {
        called := false
        f(func() error {
                called = true
                return nil
        })

}

gc considers called to be both set and used although nowhere in the scope is the value of called ever consulted.

gccgo-5.0 on the other hand considers this code to be faulty

% env LD_LIBRARY_PATH=/opt/gccgo/lib64 PATH=$PATH:/opt/gccgo/bin go build -compiler=gccgo /tmp/x.go
# command-line-arguments
/tmp/x.go:8:2: error: ‘called’ declared and not used
  called := false
  ^

gccgo version

% env LD_LIBRARY_PATH=/opt/gccgo/lib64 PATH=$PATH:/opt/gccgo/bin gccgo -v
Using built-in specs.
COLLECT_GCC=gccgo
COLLECT_LTO_WRAPPER=/opt/gccgo/libexec/gcc/x86_64-unknown-linux-gnu/5.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc/trunk/configure --prefix=/opt/gccgo --enable-languages=c,c++,go --disable-bootstrap
Thread model: posix
gcc version 5.0.0 20150324 (experimental) (GCC) 

[minux]

Dup of #3059?

[davecheney]

Yup, its a duplicate.

[minux]

(I assume you reopened this issue accidentally.)