gopls/rename: include filename in error message

Error messages now display the filename along with the package name
when a rename is blocked.

Fixes golang/go#69563

Change-Id: I00277281a78134271f7a0a7e8497a5863e48b92d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/615686
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>

Author: golopot

gopls/internal/golang/rename_check.go

@@ -866,9 +866,17 @@ func (r *renamer) satisfy() map[satisfy.Constraint]bool {
 			//
 			// Only proceed if all packages have no errors.
 			if len(pkg.ParseErrors()) > 0 || len(pkg.TypeErrors()) > 0 {
+				var filename string
+				if len(pkg.ParseErrors()) > 0 {
+					err := pkg.ParseErrors()[0][0]
+					filename = filepath.Base(err.Pos.Filename)
+				} else if len(pkg.TypeErrors()) > 0 {
+					err := pkg.TypeErrors()[0]
+					filename = filepath.Base(err.Fset.File(err.Pos).Name())
+				}
 				r.errorf(token.NoPos, // we don't have a position for this error.
-					"renaming %q to %q not possible because %q has errors",
-					r.from, r.to, pkg.Metadata().PkgPath)
+					"renaming %q to %q not possible because %q in %q has errors",
+					r.from, r.to, filename, pkg.Metadata().PkgPath)
 				return nil
 			}
 			f.Find(pkg.TypesInfo(), pkg.Syntax())

gopls/internal/test/marker/testdata/rename/bad.txt

@@ -11,9 +11,19 @@ package bad
 type myStruct struct {
 }
 
-func (s *myStruct) sFunc() bool { //@renameerr("sFunc", "rFunc", re"not possible")
+func (s *myStruct) sFunc() bool { //@renameerr("sFunc", "rFunc", "not possible because \"bad.go\" in \"golang.org/lsptests/bad\" has errors")
 	return s.Bad //@diag("Bad", re"no field or method")
 }
 
 -- bad_test.go --
 package bad
+
+
+-- badsyntax/badsyntax.go --
+package badsyntax
+
+type S struct {}
+
+func (s *S) sFunc() bool { //@renameerr("sFunc", "rFunc", "not possible because \"badsyntax.go\" in \"golang.org/lsptests/bad/badsyntax\" has errors")
+	# //@diag("#", re"expected statement, found")
+}