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S1008 should know that builtins like len and cap never return negative values #1422

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mvdan opened this issue Jul 9, 2023 · 0 comments · Fixed by #1423
Closed

S1008 should know that builtins like len and cap never return negative values #1422

mvdan opened this issue Jul 9, 2023 · 0 comments · Fixed by #1423
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bug needs-triage Newly filed issue that needs triage

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@mvdan
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mvdan commented Jul 9, 2023 

$ staticcheck -debug.version
staticcheck (devel, v0.5.0-0.dev.0.20230706211743-ddee6bbaa341)

Compiled with Go version: devel go1.21-5c15498609 Fri Jul 7 22:02:26 2023 +0000
Main module:
	honnef.co/go/tools@v0.5.0-0.dev.0.20230706211743-ddee6bbaa341 (sum: h1:jNlTAPEjbDiN9qda/1wple0GSpewFnWhvc1GO7bZX1U=)
Dependencies:
	github.com/BurntSushi/toml@v1.2.1 (sum: h1:9F2/+DoOYIOksmaJFPw1tGFy1eDnIJXg+UHjuD8lTak=)
	golang.org/x/exp/typeparams@v0.0.0-20221208152030-732eee02a75a (sum: h1:Jw5wfR+h9mnIYH+OtGT2im5wV1YGGDora5vTv/aa5bE=)
	golang.org/x/mod@v0.10.0 (sum: h1:lFO9qtOdlre5W1jxS3r/4szv2/6iXxScdzjoBMXNhYk=)
	golang.org/x/sys@v0.8.0 (sum: h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=)
	golang.org/x/tools@v0.9.4-0.20230601214343-86c93e8732cc (sum: h1:mqZawFxUzsv+YVwGQO30cZegeV/YD6dAwsdGxi0tQQg=)
$ go env
GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/mvdan/.cache/go-build'
GOENV='/home/mvdan/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/mvdan/go/pkg/mod'
GONOPROXY='github.com/cue-unity'
GONOSUMDB='github.com/cue-unity'
GOOS='linux'
GOPATH='/home/mvdan/go'
GOPRIVATE='github.com/cue-unity'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/mvdan/tip'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/mvdan/tip/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='devel go1.21-5c15498609 Fri Jul 7 22:02:26 2023 +0000'
GCCGO='gccgo'
GOAMD64='v3'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/mvdan/src/voc-node/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build75460387=/tmp/go-build -gno-record-gcc-switches'

As discussed in Slack, I got a suggestion like:

should use 'return len(t) <= 0' instead of 'if len(t) > 0 { return false }; return true' (S1008)

Most Go developers would write len(t) == 0 instead of len(t) <= 0, since we know that builtins like len or cap cannot return negative values. Staticcheck should know the same.
@mvdan mvdan added bug needs-triage Newly filed issue that needs triage labels Jul 9, 2023
mvdan added a commit to mvdan/go-tools that referenced this issue Jul 9, 2023
@mvdan
simple: reverse "len(x) > 0" as "len(x) == 0"
8973eb5 
Rather than "len(x) <= 0", which is technically correct,
but not actually what most Go programmers would write,
since funcs like len or cap can never return negative integers.

Do the same for cap and copy, which never return negative ints either.

Fixes dominikh#1422.
@mvdan mvdan mentioned this issue Jul 9, 2023
Merged
dominikh pushed a commit that referenced this issue Jul 9, 2023
@mvdan @dominikh
simple: reverse "len(x) > 0" as "len(x) == 0"
bc75918 
Rather than "len(x) <= 0", which is technically correct,
but not actually what most Go programmers would write,
since funcs like len or cap can never return negative integers.

Do the same for cap and copy, which never return negative ints either.

Fixes #1422.
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simple: reverse "len(x) > 0" as "len(x) == 0" mvdan/go-tools
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