x/tools/internal/refactor/inline: missing shadowing check when forming qualified identifiers

[adonovan]

The inliner fails to detect that the reference to Split in the path.Dir function, which is turned into path.Split in the caller, is shadowed by the parameter name path:

xtools$ go run ./gopls fix -a -d /Users/adonovan/w/xtools/go/buildutil/util.go:#2005 refactor.inline
2023/09/15 17:15:27 inline path.Dir(filepath.ToSlash(filename)) @ /Users/adonovan/w/xtools/go/buildutil/util.go:66:22
2023/09/15 17:15:27 - replace id "Split" @ #42 to "path.Split"
2023/09/15 17:15:27 - replace id "Clean" @ #62 to "path.Clean"
2023/09/15 17:15:27 keeping param "path": argument filepath.ToSlash(filename) is impure
2023/09/15 17:15:27 strategy: literalization
--- /Users/adonovan/w/xtools/go/buildutil/util.go.orig
+++ /Users/adonovan/w/xtools/go/buildutil/util.go
@@ -63,7 +63,10 @@
 	// paths will not use `\` unless the PathSeparator
 	// is also `\`, thus we can rely on filepath.ToSlash for some sanity.
 
-	dirSlash := path.Dir(filepath.ToSlash(filename)) + "/"
+	dirSlash := func(path string) string {
+		dir, _ := path.Split(path)
+		return path.Clean(dir)
+	}(filepath.ToSlash(filename)) + "/"
 
 	// We assume that no source root (GOPATH[i] or GOROOT) contains any other.
 	for _, srcdir := range ctxt.SrcDirs() {
xtools$ 

The fix is to tabulate for each free name all the shadowing definitions (like we do for parameters) and check whether the introduced package name is in that set.

[gopherbot]

Change https://go.dev/cl/531455 mentions this issue: internal/refactor/inline: fix pkgname shadowing bug