diff --git a/src/cmd/compile/internal/gc/go.go b/src/cmd/compile/internal/gc/go.go
index fdea1f2..f4b3dc9 100644
--- a/src/cmd/compile/internal/gc/go.go
+++ b/src/cmd/compile/internal/gc/go.go
@@ -66,6 +66,14 @@
 	Syms     map[string]*Sym
 }
 
+// Sym represents an object name. Most commonly, this is a Go identifier naming
+// an object declared within a package, but Syms are also used to name internal
+// synthesized objects.
+//
+// As a special exception, field and method names that are exported use the Sym
+// associated with localpkg instead of the package that declared them. This
+// allows using Sym pointer equality to test for Go identifier uniqueness when
+// handling selector expressions.
 type Sym struct {
 	Flags     SymFlags
 	Link      *Sym
@@ -111,8 +119,6 @@
 	SymAlgGen
 )
 
-var dclstack *Sym
-
 // Ctype describes the constant kind of an "ideal" (untyped) constant.
 type Ctype int8