cmd/compile: unexport Type.Vargen

This field is only used outside of packages types in two places, and
they follow the same pattern. So this CL creates a Type.Setvargen
function that they can use instead, so that Type.Vargen can be
unexported.

A bit clumsy, but it works for now.

Change-Id: I7b4f33fac635e2464df2fbc0607ab40902f6f09f
Reviewed-on: https://go-review.googlesource.com/c/go/+/345469
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>

src/cmd/compile/internal/noder/decl.go

@@ -154,8 +154,7 @@ func (g *irgen) typeDecl(out *ir.Nodes, decl *syntax.TypeDecl) {
 	name, obj := g.def(decl.Name)
 	ntyp, otyp := name.Type(), obj.Type()
 	if ir.CurFunc != nil {
-		typecheck.TypeGen++
-		ntyp.Vargen = typecheck.TypeGen
+		ntyp.SetVargen()
 	}
 
 	pragmas := g.pragmaFlags(decl.Pragma, typePragmas)

src/cmd/compile/internal/typecheck/typecheck.go

@@ -1736,11 +1736,6 @@ func CheckMapKeys() {
 	mapqueue = nil
 }
 
-// TypeGen tracks the number of function-scoped defined types that
-// have been declared. It's used to generate unique linker symbols for
-// their runtime type descriptors.
-var TypeGen int32
-
 func typecheckdeftype(n *ir.Name) {
 	if base.EnableTrace && base.Flag.LowerT {
 		defer tracePrint("typecheckdeftype", n)(nil)
@@ -1748,8 +1743,7 @@ func typecheckdeftype(n *ir.Name) {
 
 	t := types.NewNamed(n)
 	if n.Curfn != nil {
-		TypeGen++
-		t.Vargen = TypeGen
+		t.SetVargen()
 	}
 
 	if n.Pragma()&ir.NotInHeap != 0 {

src/cmd/compile/internal/types/fmt.go

@@ -361,8 +361,8 @@ func tconv2(b *bytes.Buffer, t *Type, verb rune, mode fmtMode, visited map[*Type
 		// output too. It seems like it should, but that mode is currently
 		// used in string representation used by reflection, which is
 		// user-visible and doesn't expect this.
-		if mode == fmtTypeID && t.Vargen != 0 {
-			fmt.Fprintf(b, "·%d", t.Vargen)
+		if mode == fmtTypeID && t.vargen != 0 {
+			fmt.Fprintf(b, "·%d", t.vargen)
 		}
 		return
 	}

src/cmd/compile/internal/types/type.go

@@ -178,7 +178,7 @@ type Type struct {
 	}
 
 	sym    *Sym  // symbol containing name, for named types
-	Vargen int32 // unique name for OTYPE/ONAME
+	vargen int32 // unique name for OTYPE/ONAME
 
 	kind  Kind  // kind of type
 	Align uint8 // the required alignment of this type, in bytes (0 means Width and Align have not yet been computed)
@@ -1221,8 +1221,8 @@ func (t *Type) cmp(x *Type) Cmp {
 
 	if x.sym != nil {
 		// Syms non-nil, if vargens match then equal.
-		if t.Vargen != x.Vargen {
-			return cmpForNe(t.Vargen < x.Vargen)
+		if t.vargen != x.vargen {
+			return cmpForNe(t.vargen < x.vargen)
 		}
 		return CMPeq
 	}
@@ -1768,6 +1768,25 @@ func (t *Type) Obj() Object {
 	return nil
 }
 
+// typeGen tracks the number of function-scoped defined types that
+// have been declared. It's used to generate unique linker symbols for
+// their runtime type descriptors.
+var typeGen int32
+
+// SetVargen assigns a unique generation number to type t, which must
+// be a defined type declared within function scope. The generation
+// number is used to distinguish it from other similarly spelled
+// defined types from the same package.
+//
+// TODO(mdempsky): Come up with a better solution.
+func (t *Type) SetVargen() {
+	base.Assertf(t.Sym() != nil, "SetVargen on anonymous type %v", t)
+	base.Assertf(t.vargen == 0, "type %v already has Vargen %v", t, t.vargen)
+
+	typeGen++
+	t.vargen = typeGen
+}
+
 // SetUnderlying sets the underlying type. SetUnderlying automatically updates any
 // types that were waiting for this type to be completed.
 func (t *Type) SetUnderlying(underlying *Type) {