fix: improve switch and type switch statement processing

_test/switch34.go

@@ -0,0 +1,13 @@
+package main
+
+func main() {
+	var a interface{}
+	switch a.(type) {
+	case []int:
+	case []string:
+	}
+	println("bye")
+}
+
+// Output:
+// bye

interp/cfg.go

@@ -1467,6 +1467,7 @@ func (interp *Interpreter) cfg(root *node, pkgID string) ([]*node, error) {
 				}
 			}
 			c := clauses[l-1] // Last clause.
+			c.fnext = n
 			if len(c.child) == 0 {
 				c.tnext = n // Clause body is empty, exit.
 			} else {

interp/run.go

@@ -2059,11 +2059,12 @@ func _case(n *node) {
 				// match against multiple types: assign var to interface value
 				n.exec = func(f *frame) bltn {
 					val := srcValue(f)
-					vid := val.Interface().(valueInterface).node.typ.id()
-					for _, typ := range types {
-						if vid == typ.id() {
-							destValue(f).Set(val)
-							return tnext
+					if v := srcValue(f).Interface().(valueInterface).node; v != nil {
+						for _, typ := range types {
+							if v.typ.id() == typ.id() {
+								destValue(f).Set(val)
+								return tnext
+							}
 						}
 					}
 					return fnext
@@ -2075,10 +2076,11 @@ func _case(n *node) {
 				n.exec = func(f *frame) bltn { return tnext }
 			} else {
 				n.exec = func(f *frame) bltn {
-					vtyp := srcValue(f).Interface().(valueInterface).node.typ
-					for _, typ := range types {
-						if vtyp.id() == typ.id() {
-							return tnext
+					if v := srcValue(f).Interface().(valueInterface).node; v != nil {
+						for _, typ := range types {
+							if v.typ.id() == typ.id() {
+								return tnext
+							}
 						}
 					}
 					return fnext

interp/type.go

@@ -845,17 +845,43 @@ func (t *itype) methods() methodSet {
 }
 
 // id returns a unique type identificator string
-func (t *itype) id() string {
-	// TODO: if res is nil, build identity from String()
-
-	res := ""
+func (t *itype) id() (res string) {
+	if t.name != "" {
+		return t.path + "." + t.name
+	}
 	switch t.cat {
-	case valueT:
-		res = t.rtype.PkgPath() + "." + t.rtype.Name()
+	case arrayT:
+		res = "[" + strconv.Itoa(t.size) + "]" + t.val.id()
+	case chanT:
+		res = "<-" + t.val.id()
+	case funcT:
+		res = "func("
+		for _, t := range t.arg {
+			res += t.id() + ","
+		}
+		res += ")("
+		for _, t := range t.ret {
+			res += t.id() + ","
+		}
+		res += ")"
+	case interfaceT:
+		res = "interface{"
+		for _, t := range t.field {
+			res += t.name + " " + t.typ.id() + ";"
+		}
+		res += "}"
+	case mapT:
+		res = "map[" + t.key.id() + "]" + t.val.id()
 	case ptrT:
 		res = "*" + t.val.id()
-	default:
-		res = t.path + "." + t.name
+	case structT:
+		res = "struct{"
+		for _, t := range t.field {
+			res += t.name + " " + t.typ.id() + ";"
+		}
+		res += "}"
+	case valueT:
+		res = t.rtype.PkgPath() + "." + t.rtype.Name()
 	}
 	return res
 }