Fix bug in msgpack invalid value error.

Our invalid value type error when marshaling to msgpack is supposed to
tell people what type they passed in. Unfortunately, we're telling them
the type of the Value they passed in, which is always tftypes.Value, not
the *contents* of that Value, which is the actual type they should know
about. This leads to confusing error messages that aren't actually
helpful.

Switching to pass in the content of the tftypes.Value gives a much
better error message.

Author: Paddy Carver

tfprotov5/tftypes/value_msgpack.go

@@ -51,7 +51,7 @@ func marshalMsgPack(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 func marshalMsgPackDynamicPseudoType(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 	dst, ok := val.value.(Value)
 	if !ok {
-		return unexpectedValueTypeError(p, Value{}, val, typ)
+		return unexpectedValueTypeError(p, Value{}, val.value, typ)
 	}
 	typeJSON, err := dst.typ.MarshalJSON()
 	if err != nil {
@@ -75,7 +75,7 @@ func marshalMsgPackDynamicPseudoType(val Value, typ Type, p Path, enc *msgpack.E
 func marshalMsgPackString(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 	s, ok := val.value.(string)
 	if !ok {
-		return unexpectedValueTypeError(p, s, val, typ)
+		return unexpectedValueTypeError(p, s, val.value, typ)
 	}
 	err := enc.EncodeString(s)
 	if err != nil {
@@ -93,7 +93,7 @@ func marshalMsgPackNumber(val Value, typ Type, p Path, enc *msgpack.Encoder) err
 	// advantage of that...
 	n, ok := val.value.(*big.Float)
 	if !ok {
-		return unexpectedValueTypeError(p, n, val, typ)
+		return unexpectedValueTypeError(p, n, val.value, typ)
 	}
 	if iv, acc := n.Int64(); acc == big.Exact {
 		err := enc.EncodeInt(iv)
@@ -117,7 +117,7 @@ func marshalMsgPackNumber(val Value, typ Type, p Path, enc *msgpack.Encoder) err
 func marshalMsgPackBool(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 	b, ok := val.value.(bool)
 	if !ok {
-		return unexpectedValueTypeError(p, b, val, typ)
+		return unexpectedValueTypeError(p, b, val.value, typ)
 	}
 	err := enc.EncodeBool(b)
 	if err != nil {
@@ -129,7 +129,7 @@ func marshalMsgPackBool(val Value, typ Type, p Path, enc *msgpack.Encoder) error
 func marshalMsgPackList(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 	l, ok := val.value.([]Value)
 	if !ok {
-		return unexpectedValueTypeError(p, l, val, typ)
+		return unexpectedValueTypeError(p, l, val.value, typ)
 	}
 	err := enc.EncodeArrayLen(len(l))
 	if err != nil {
@@ -149,7 +149,7 @@ func marshalMsgPackList(val Value, typ Type, p Path, enc *msgpack.Encoder) error
 func marshalMsgPackSet(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 	s, ok := val.value.([]Value)
 	if !ok {
-		return unexpectedValueTypeError(p, s, val, typ)
+		return unexpectedValueTypeError(p, s, val.value, typ)
 	}
 	err := enc.EncodeArrayLen(len(s))
 	if err != nil {
@@ -169,7 +169,7 @@ func marshalMsgPackSet(val Value, typ Type, p Path, enc *msgpack.Encoder) error
 func marshalMsgPackMap(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 	m, ok := val.value.(map[string]Value)
 	if !ok {
-		return unexpectedValueTypeError(p, m, val, typ)
+		return unexpectedValueTypeError(p, m, val.value, typ)
 	}
 	err := enc.EncodeMapLen(len(m))
 	if err != nil {
@@ -193,7 +193,7 @@ func marshalMsgPackMap(val Value, typ Type, p Path, enc *msgpack.Encoder) error
 func marshalMsgPackTuple(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 	t, ok := val.value.([]Value)
 	if !ok {
-		return unexpectedValueTypeError(p, t, val, typ)
+		return unexpectedValueTypeError(p, t, val.value, typ)
 	}
 	types := typ.(Tuple).ElementTypes
 	err := enc.EncodeArrayLen(len(types))
@@ -215,7 +215,7 @@ func marshalMsgPackTuple(val Value, typ Type, p Path, enc *msgpack.Encoder) erro
 func marshalMsgPackObject(val Value, typ Type, p Path, enc *msgpack.Encoder) error {
 	o, ok := val.value.(map[string]Value)
 	if !ok {
-		return unexpectedValueTypeError(p, o, val, typ)
+		return unexpectedValueTypeError(p, o, val.value, typ)
 	}
 	types := typ.(Object).AttributeTypes
 	keys := make([]string, 0, len(types))