@hyangah -It looks like actionable message. I am making changes for this. Kindly assign this to me.
Even for undeclared name too, we can change into an actionable message "Add missing declaration ..."

By the way, as this message got changed go-staticcheck uses the same string undefined and those bring out warning. Kindly suggest.

Looking at the logic in gopls that creates this patch--in the undeclared analyzer--it seems that it already gives a reasonable name to the fix, but this must be getting lost somewhere along the plumbing between the analyzer and the LSP:

https://cs.opensource.google/go/x/tools/+/refs/tags/gopls/v0.15.0-pre.1:gopls/internal/analysis/undeclaredname/undeclared.go;l=146-156

	return fset, &analysis.SuggestedFix{
		Message: fmt.Sprintf("Create function \"%s\"", ident.Name),
		TextEdits: []analysis.TextEdit{{
			Pos:     pos,
			End:     pos,
			NewText: b.Bytes(),
		}},
	}, nil

@alandonovan , Thanks. The place you are referring comes in while apply Fix, correct me if I can understand this better.

I tried applying the fix locally and it goes in runForError() and change error message for functions undeclared

@hyangah Is this expected ?

pass.Report(analysis.Diagnostic{
		Pos:     err.Pos,
		End:     end,
		Message: err.Msg,
	})

Thanks @raghvenders
Create function "%s" as proposed by the analyzer seems more concise.

Change https://go.dev/cl/556755 mentions this issue: gopls/internal/lsp/source: fix Fix