cmd/compile: eliminate methtype's mustname parameter

Change-Id: Idd3e677dec00eb36a2cf7baa34e772335e1f2bc8
Reviewed-on: https://go-review.googlesource.com/28173
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/dcl.go

@@ -1168,8 +1168,8 @@ func addmethod(msym *Sym, t *Type, tpkg *Pkg, local, nointerface bool) {
 	}
 
 	pa := rf.Type // base type
-	mt := methtype(pa, 1)
-	if mt == nil {
+	mt := methtype(pa)
+	if mt == nil || mt.Sym == nil {
 		t = pa
 		if t == nil { // rely on typecheck having complained before
 			return

src/cmd/compile/internal/gc/reflect.go

@@ -282,7 +282,7 @@ func methodfunc(f *Type, receiver *Type) *Type {
 // Generates stub functions as needed.
 func methods(t *Type) []*Sig {
 	// method type
-	mt := methtype(t, 0)
+	mt := methtype(t)
 
 	if mt == nil {
 		return nil

src/cmd/compile/internal/gc/subr.go

@@ -589,14 +589,15 @@ func isblanksym(s *Sym) bool {
 	return s != nil && s.Name == "_"
 }
 
-// given receiver of type t (t == r or t == *r)
-// return type to hang methods off (r).
-func methtype(t *Type, mustname int) *Type {
+// methtype returns the underlying type, if any,
+// that owns methods with receiver parameter t.
+// The result is either a named type or an anonymous struct.
+func methtype(t *Type) *Type {
 	if t == nil {
 		return nil
 	}
 
-	// strip away pointer if it's there
+	// Strip away pointer if it's there.
 	if t.IsPtr() {
 		if t.Sym != nil {
 			return nil
@@ -607,29 +608,20 @@ func methtype(t *Type, mustname int) *Type {
 		}
 	}
 
-	// need a type name
-	if t.Sym == nil && (mustname != 0 || !t.IsStruct()) {
+	// Must be a named type or anonymous struct.
+	if t.Sym == nil && !t.IsStruct() {
 		return nil
 	}
 
-	// check types
-	if !issimple[t.Etype] {
-		switch t.Etype {
-		default:
-			return nil
-
-		case TSTRUCT,
-			TARRAY,
-			TSLICE,
-			TMAP,
-			TCHAN,
-			TSTRING,
-			TFUNC:
-			break
-		}
+	// Check types.
+	if issimple[t.Etype] {
+		return t
 	}
-
-	return t
+	switch t.Etype {
+	case TARRAY, TCHAN, TFUNC, TMAP, TSLICE, TSTRING, TSTRUCT:
+		return t
+	}
+	return nil
 }
 
 func cplxsubtype(et EType) EType {
@@ -1487,7 +1479,7 @@ func lookdot0(s *Sym, t *Type, save **Field, ignorecase bool) int {
 		}
 	}
 
-	u = methtype(t, 0)
+	u = methtype(t)
 	if u != nil {
 		for _, f := range u.Methods().Slice() {
 			if f.Embedded == 0 && (f.Sym == s || (ignorecase && strings.EqualFold(f.Sym.Name, s.Name))) {
@@ -1653,7 +1645,7 @@ func expand0(t *Type, followptr bool) {
 		return
 	}
 
-	u = methtype(t, 0)
+	u = methtype(t)
 	if u != nil {
 		for _, f := range u.Methods().Slice() {
 			if f.Sym.Flags&SymUniq != 0 {
@@ -2015,7 +2007,7 @@ func implements(t, iface *Type, m, samename **Field, ptr *int) bool {
 		return true
 	}
 
-	t = methtype(t, 0)
+	t = methtype(t)
 	if t != nil {
 		expandmeth(t)
 	}

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

@@ -2359,7 +2359,7 @@ func looktypedot(n *Node, t *Type, dostrcmp int) bool {
 
 	// Find the base type: methtype will fail if t
 	// is not of the form T or *T.
-	mt := methtype(t, 0)
+	mt := methtype(t)
 	if mt == nil {
 		return false
 	}
@@ -2410,7 +2410,7 @@ func lookdot(n *Node, t *Type, dostrcmp int) *Field {
 
 	var f2 *Field
 	if n.Left.Type == t || n.Left.Type.Sym == nil {
-		mt := methtype(t, 0)
+		mt := methtype(t)
 		if mt != nil {
 			// Use f2->method, not f2->xmethod: adddot has
 			// already inserted all the necessary embedded dots.