For *csv.ParseError, error.Is() comes back false and error.As() comes back true? #42004
Description
What version of Go are you using (go version)?
$ go version go version go1.15.3 linux/amd64
Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (go env)?
go env Output
$ go env GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/home/corey/.cache/go-build" GOENV="/home/corey/.config/go/env" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GOINSECURE="" GOMODCACHE="/home/corey/go/pkg/mod" GONOPROXY="gitlab.com/ethopass/*" GONOSUMDB="gitlab.com/ethopass/*" GOOS="linux" GOPATH="/home/corey/go" GOPRIVATE="gitlab.com/ethopass/*" GOPROXY="https://proxy.golang.org,direct" GOROOT="/usr/local/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64" GCCGO="gccgo" AR="ar" CC="gcc" CXX="g++" CGO_ENABLED="1" GOMOD="" 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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build937491866=/tmp/go-build -gno-record-gcc-switches"
What did you do?
https://play.golang.org/p/SdpH9lJMVu1
I setup a reader that expects 2 fields per record and gave it some data with only 1 field. The csv.Reader returns a *csv.ParseError that contians the details about not containing enough fields.
When comparing against an empty *csv.ParseError, errors.Is() returns false and errors.As() returns true.
What did you expect to see?
I had the understanding that errors.Is and errors.As would return the same bool values when passed similar parameters indicating that the error is of that type. Either both would return true or both would return false. In this setup, I expected errors.Is(err, &csv.ParseError{}) to return true because the error is indeed a *csv.ParseError.
What did you see instead?
Instead, I find that errors.Is() returns false and errors.As() returns true when given similar parameters.