diff --git a/src/cmd/compile/internal/gc/go.go b/src/cmd/compile/internal/gc/go.go
index b6b858c0d9..5c273bbd30 100644
--- a/src/cmd/compile/internal/gc/go.go
+++ b/src/cmd/compile/internal/gc/go.go
@@ -67,7 +67,7 @@ type Label struct {
 	Breakpc  *obj.Prog // pointer to code
 	Continpc *obj.Prog // pointer to code
 
-	Used bool
+	Used bool // for "label defined and not used" error
 }
 
 type SymFlags uint8
diff --git a/src/cmd/compile/internal/gc/syntax.go b/src/cmd/compile/internal/gc/syntax.go
index 79d9d8ce20..001e15b327 100644
--- a/src/cmd/compile/internal/gc/syntax.go
+++ b/src/cmd/compile/internal/gc/syntax.go
@@ -60,12 +60,12 @@ type Node struct {
 	Colas     bool  // OAS resulting from :=
 	Diag      uint8 // already printed error about this
 	Noescape  bool  // func arguments do not escape; TODO(rsc): move Noescape to Func struct (see CL 7360)
-	Walkdef   uint8
-	Typecheck uint8
+	Walkdef   uint8 // tracks state during typecheckdef; 2 == loop detected
+	Typecheck uint8 // tracks state during typechecking; 2 == loop detected
 	Local     bool
 	IsStatic  bool // whether this Node will be converted to purely static data
 	Initorder uint8
-	Used      bool
+	Used      bool // for variable/label declared and not used error
 	Isddd     bool // is the argument variadic
 	Implicit  bool
 	Addrtaken bool  // address taken, even if not moved to heap