semver: remove unused err field

The err field is assigned in the parse function but never used on another function.

Change-Id: I1ea5fa922776c2c83f5269724f856e8d667f43b4
Reviewed-on: https://go-review.googlesource.com/c/mod/+/353749
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Trust: Jay Conrod <jayconrod@google.com>
Trust: Michael Knyszek <mknyszek@google.com>

semver/semver.go

@@ -32,7 +32,6 @@ type parsed struct {
 	short      string
 	prerelease string
 	build      string
-	err        string
 }
 
 // IsValid reports whether v is a valid semantic version string.
@@ -172,12 +171,10 @@ func Sort(list []string) {
 
 func parse(v string) (p parsed, ok bool) {
 	if v == "" || v[0] != 'v' {
-		p.err = "missing v prefix"
 		return
 	}
 	p.major, v, ok = parseInt(v[1:])
 	if !ok {
-		p.err = "bad major version"
 		return
 	}
 	if v == "" {
@@ -187,13 +184,11 @@ func parse(v string) (p parsed, ok bool) {
 		return
 	}
 	if v[0] != '.' {
-		p.err = "bad minor prefix"
 		ok = false
 		return
 	}
 	p.minor, v, ok = parseInt(v[1:])
 	if !ok {
-		p.err = "bad minor version"
 		return
 	}
 	if v == "" {
@@ -202,31 +197,26 @@ func parse(v string) (p parsed, ok bool) {
 		return
 	}
 	if v[0] != '.' {
-		p.err = "bad patch prefix"
 		ok = false
 		return
 	}
 	p.patch, v, ok = parseInt(v[1:])
 	if !ok {
-		p.err = "bad patch version"
 		return
 	}
 	if len(v) > 0 && v[0] == '-' {
 		p.prerelease, v, ok = parsePrerelease(v)
 		if !ok {
-			p.err = "bad prerelease"
 			return
 		}
 	}
 	if len(v) > 0 && v[0] == '+' {
 		p.build, v, ok = parseBuild(v)
 		if !ok {
-			p.err = "bad build"
 			return
 		}
 	}
 	if v != "" {
-		p.err = "junk on end"
 		ok = false
 		return
 	}