cmd/go: program that shadows 'string' type fails to compile with go 1.11

[zigo101]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.11 linux/amd64

Does this issue reproduce with the latest release?

yes

What did you do?

package main

type string = []int

func main() {
}

What did you expect to see?

run okay.

What did you see instead?

build error:

/tmp/go-build910164881/b001/_gomod_.go:7:24: cannot use "0w\xaf\f\x92t\b\x02A\xe1\xc1\a\xe6\xd6\x18\xe6path\tapp\nmod\tapp\t(devel)\t\n\xf92C1\x86\x18 r\x00\x82B\x10A\x16\xd8\xf2" (type string) as type []int in assignment

It runs okay with Go 1.10.3.

[agnivade]

I am unable to reproduce this.

[zigo101]

It is only reproducible if the code is outside of GOPATH.

[agnivade]

Still cannot reproduce.

[bmeh]

I cannot reproduce this error either using the same version, outside $GOPATH.

Could you please:

1. provide the output of go env
2. re-build it using go build -work file.go (-work will make sure the temporary work directory does not get deleted), and post the content of $WORK/b001/_gomod_.go? Depending on the amount of lines, you may want to use a pastebin.

I am not exactly sure how go build works, but perhaps it may be a good starting point.

[zigo101]

It looks it is not 100% reproducible.

I checked it on another computer, with the following tries, all are outside of GOPATH.

1. A single main.go, go run main.go runs okay.
2. Add a go.mod file, go run main.go prints the errors mentioned above.
3. Remove the go.mod file, go run main.go runs okay again.
4. Add back again the go.mod file, go run main.go continues to run okay.

On the first computer (not nearby now), go run main.go always prints the errors, whether the go.mod file exists or not. (When the first time the errors were printed, the go.mod file had existed there already.)

So I doubt that this problem might be related to cache.

[agnivade]

For the cases, where you are able to reproduce, please provide the output by adding the -x flag.

[zigo101]

Another one:

$ go run -work -x y.go 
WORK=/tmp/go-build148841673
mkdir -p $WORK/b001/
cat >$WORK/b001/_gomod_.go << 'EOF' # internal

		package main
		import _ "unsafe"
		//go:linkname __debug_modinfo__ runtime/debug.modinfo
		var __debug_modinfo__ string
		func init() {
			__debug_modinfo__ = "0w\xaf\f\x92t\b\x02A\xe1\xc1\a\xe6\xd6\x18\xe6path\ta.b.c\nmod\ta.b.c\t(devel)\t\n\xf92C1\x86\x18 r\x00\x82B\x10A\x16\xd8\xf2"
		}
	EOF
cat >$WORK/b001/importcfg << 'EOF' # internal
# import config
packagefile runtime=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime.a
EOF
cd /home/username/Desktop/y
/home/username/sdks/go-1.11/pkg/tool/linux_amd64/compile -o $WORK/b001/_pkg_.a -trimpath $WORK/b001 -p main -complete -buildid UHBYAsCe0dpuN23Mt_yP/UHBYAsCe0dpuN23Mt_yP -dwarf=false -goversion go1.11 -D _/home/username/Desktop/y -importcfg $WORK/b001/importcfg -pack -c=2 ./y.go $WORK/b001/_gomod_.go
# command-line-arguments
/tmp/go-build148841673/b001/_gomod_.go:7:24: cannot use "0w\xaf\f\x92t\b\x02A\xe1\xc1\a\xe6\xd6\x18\xe6path\ta.b.c\nmod\ta.b.c\t(devel)\t\n\xf92C1\x86\x18 r\x00\x82B\x10A\x16\xd8\xf2" (type string) as type []int in assignment

[zigo101]

The new errors are some different:

$ go run -work -x z.go 
WORK=/tmp/go-build881444167
mkdir -p $WORK/b001/
cat >$WORK/b001/importcfg << 'EOF' # internal
# import config
packagefile runtime=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime.a
EOF
cd /home/username/Desktop/z
/home/username/sdks/go-1.11/pkg/tool/linux_amd64/compile -o $WORK/b001/_pkg_.a -trimpath $WORK/b001 -p main -complete -buildid gNMKr6CFxeFcxHT43CI4/gNMKr6CFxeFcxHT43CI4 -dwarf=false -goversion go1.11 -D _/home/username/Desktop/z -importcfg $WORK/b001/importcfg -pack -c=2 ./z.go
/home/username/sdks/go-1.11/pkg/tool/linux_amd64/buildid -w $WORK/b001/_pkg_.a # internal
cp $WORK/b001/_pkg_.a /home/username/.cache/go-build/08/08b252bcff057a11a79a57407ed6aa24ecb48594498f60e2b08984df4c1be67a-d # internal
cat >$WORK/b001/importcfg.link << 'EOF' # internal
packagefile command-line-arguments=$WORK/b001/_pkg_.a
packagefile runtime=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime.a
packagefile internal/bytealg=/home/username/sdks/go-1.11/pkg/linux_amd64/internal/bytealg.a
packagefile internal/cpu=/home/username/sdks/go-1.11/pkg/linux_amd64/internal/cpu.a
packagefile runtime/internal/atomic=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime/internal/atomic.a
packagefile runtime/internal/sys=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime/internal/sys.a
EOF
mkdir -p $WORK/b001/exe/
cd .
/home/username/sdks/go-1.11/pkg/tool/linux_amd64/link -o $WORK/b001/exe/z -importcfg $WORK/b001/importcfg.link -s -w -buildmode=exe -buildid=kct7zM2i7B1u1xUGy9_J/gNMKr6CFxeFcxHT43CI4/q74ZA2q-PWwpJ49yWZKu/kct7zM2i7B1u1xUGy9_J -extld=gcc $WORK/b001/_pkg_.a
$WORK/b001/exe/z

[zigo101]

Aha, the last one looks succeeded.

[agnivade]

Something related to having a go.mod. @bcmills @myitcv

[zigo101]

Another success but with some different messages:

go run -work -x w.go
WORK=/tmp/go-build935203608
mkdir -p $WORK/b001/
cat >$WORK/b001/_gomod_.go << 'EOF' # internal

		package main
		import _ "unsafe"
		//go:linkname __debug_modinfo__ runtime/debug.modinfo
		var __debug_modinfo__ string
		func init() {
			__debug_modinfo__ = "0w\xaf\f\x92t\b\x02A\xe1\xc1\a\xe6\xd6\x18\xe6path\tw.w.w\nmod\tw.w.w\t(devel)\t\n\xf92C1\x86\x18 r\x00\x82B\x10A\x16\xd8\xf2"
		}
	EOF
cat >$WORK/b001/importcfg << 'EOF' # internal
# import config
packagefile runtime=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime.a
EOF
cd /home/username/Desktop/w
/home/username/sdks/go-1.11/pkg/tool/linux_amd64/compile -o $WORK/b001/_pkg_.a -trimpath $WORK/b001 -p main -complete -buildid 7QpYSWkEkSs7VIu3HqeE/7QpYSWkEkSs7VIu3HqeE -dwarf=false -goversion go1.11 -D _/home/username/Desktop/w -importcfg $WORK/b001/importcfg -pack -c=2 ./w.go $WORK/b001/_gomod_.go
/home/username/sdks/go-1.11/pkg/tool/linux_amd64/buildid -w $WORK/b001/_pkg_.a # internal
cp $WORK/b001/_pkg_.a /home/username/.cache/go-build/bb/bb36be7532d0a4e187e9fa2839bde821522aec3ca06b0345bc2e9e2162d825c8-d # internal
cat >$WORK/b001/importcfg.link << 'EOF' # internal
packagefile command-line-arguments=$WORK/b001/_pkg_.a
packagefile runtime=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime.a
packagefile internal/bytealg=/home/username/sdks/go-1.11/pkg/linux_amd64/internal/bytealg.a
packagefile internal/cpu=/home/username/sdks/go-1.11/pkg/linux_amd64/internal/cpu.a
packagefile runtime/internal/atomic=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime/internal/atomic.a
packagefile runtime/internal/sys=/home/username/sdks/go-1.11/pkg/linux_amd64/runtime/internal/sys.a
EOF
mkdir -p $WORK/b001/exe/
cd .
/home/username/sdks/go-1.11/pkg/tool/linux_amd64/link -o $WORK/b001/exe/w -importcfg $WORK/b001/importcfg.link -s -w -buildmode=exe -buildid=oBvIHRhWrsxBQcAZgS1v/7QpYSWkEkSs7VIu3HqeE/4KhN7m9lZuy5Nqxw8aEL/oBvIHRhWrsxBQcAZgS1v -extld=gcc $WORK/b001/_pkg_.a
$WORK/b001/exe/w