compiler,reflect: fix NumMethods for Interface type

testdata/reflect.go

@@ -456,6 +456,7 @@ func showValue(rv reflect.Value, indent string) {
 	case reflect.Interface:
 		println(indent + "  interface")
 		println(indent+"  nil:", rv.IsNil())
+		println(indent+"  NumMethod:", rv.NumMethod())
 		if !rv.IsNil() {
 			showValue(rv.Elem(), indent+"  ")
 		}

testdata/reflect.txt

@@ -80,6 +80,7 @@ reflect type: ptr
   reflect type: interface settable=true addrable=true
     interface
     nil: true
+    NumMethod: 1
 reflect type: ptr
   pointer: true int
   nil: false
@@ -240,6 +241,7 @@ reflect type: struct
   reflect type: interface caninterface=false
     interface
     nil: true
+    NumMethod: 1
 reflect type: struct
   struct: 3
   field: 0 a
@@ -371,12 +373,14 @@ reflect type: slice comparable=false
   reflect type: interface settable=true addrable=true
     interface
     nil: false
+    NumMethod: 0
     reflect type: int
       int: 3
   indexing: 1
   reflect type: interface settable=true addrable=true
     interface
     nil: false
+    NumMethod: 0
     reflect type: string
       string: str 3
       reflect type: uint8
@@ -389,6 +393,7 @@ reflect type: slice comparable=false
   reflect type: interface settable=true addrable=true
     interface
     nil: false
+    NumMethod: 0
     reflect type: complex128
       complex: (-4.000000e+000+2.500000e+000i)
 reflect type: ptr