cmd/go: 'go mod download' can't request version of the main module #42524
Description
What version of Go are you using (go version)?
$ go version go version devel +8f2db14cd3 Tue Nov 10 18:42:47 2020 +0000 darwin/amd64
Does this issue reproduce with the latest release?
No, this is a regression.
What operating system and processor architecture are you using (go env)?
go env Output
$ go env GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/Users/jayconrod/Library/Caches/go-build" GOENV="/Users/jayconrod/Library/Application Support/go/env" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="darwin" GOINSECURE="" GOMODCACHE="/Users/jayconrod/go/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="darwin" GOPATH="/Users/jayconrod/go" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/Users/jayconrod/Code/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/Users/jayconrod/Code/go/pkg/tool/darwin_amd64" GOVCS="" GOVERSION="devel +8f2db14cd3 Tue Nov 10 18:42:47 2020 +0000" GCCGO="gccgo" AR="ar" CC="clang" CXX="clang++" CGO_ENABLED="1" GOMOD="/Users/jayconrod/Code/test/go.mod" CGO_CFLAGS="-g -O2" CGO_CPPFLAGS="" CGO_CXXFLAGS="-g -O2" CGO_FFLAGS="-g -O2" CGO_LDFLAGS="-g -O2" PKG_CONFIG="pkg-config" GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/rq/x0692kqj6ml8cvrhcqh5bswc008xj1/T/go-build788352896=/tmp/go-build -gno-record-gcc-switches -fno-common"
What did you do?
go mod init rsc.io/quote
go mod download rsc.io/quote@v1.5.2
What did you expect to see?
The module version specified on the command line is downloaded regardless of whether its path is the same as the main module.
What did you see instead?
rsc.io/quote@v1.5.2: can't request version "v1.5.2" of the main module (rsc.io/quote)