Implement `int*` and `uint*` builtin functinos

[antonmedv]

We already have int() and float() builtins. Let's add others as well: uint8, byte, int64, float64, etc.

And we can change compiler to compile int for IntegerNode, and remove this code:

func (c *compiler) IntegerNode(node *ast.IntegerNode) {
	t := node.Type()
	if t == nil {
		c.emitPush(node.Value)
		return
	}
	switch t.Kind() {
	case reflect.Float32:
		c.emitPush(float32(node.Value))
	case reflect.Float64:
		c.emitPush(float64(node.Value))
	case reflect.Int:
		c.emitPush(node.Value)
	case reflect.Int8:
		if node.Value > math.MaxInt8 || node.Value < math.MinInt8 {
			panic(fmt.Sprintf("constant %d overflows int8", node.Value))
		}
		c.emitPush(int8(node.Value))
	case reflect.Int16:
		if node.Value > math.MaxInt16 || node.Value < math.MinInt16 {
			panic(fmt.Sprintf("constant %d overflows int16", node.Value))
		}
		c.emitPush(int16(node.Value))
	case reflect.Int32:
		if node.Value > math.MaxInt32 || node.Value < math.MinInt32 {
			panic(fmt.Sprintf("constant %d overflows int32", node.Value))
		}
		c.emitPush(int32(node.Value))
	case reflect.Int64:
		if node.Value > math.MaxInt64 || node.Value < math.MinInt64 {
			panic(fmt.Sprintf("constant %d overflows int64", node.Value))
		}
		c.emitPush(int64(node.Value))
	case reflect.Uint:
		if node.Value < 0 {
			panic(fmt.Sprintf("constant %d overflows uint", node.Value))
		}
		c.emitPush(uint(node.Value))
	case reflect.Uint8:
		if node.Value > math.MaxUint8 || node.Value < 0 {
			panic(fmt.Sprintf("constant %d overflows uint8", node.Value))
		}
		c.emitPush(uint8(node.Value))
	case reflect.Uint16:
		if node.Value > math.MaxUint16 || node.Value < 0 {
			panic(fmt.Sprintf("constant %d overflows uint16", node.Value))
		}
		c.emitPush(uint16(node.Value))
	case reflect.Uint32:
		if node.Value > math.MaxUint32 || node.Value < 0 {
			panic(fmt.Sprintf("constant %d overflows uint32", node.Value))
		}
		c.emitPush(uint32(node.Value))
	case reflect.Uint64:
		if node.Value < 0 {
			panic(fmt.Sprintf("constant %d overflows uint64", node.Value))
		}
		c.emitPush(uint64(node.Value))
	default:
		c.emitPush(node.Value)
	}
}

And for function calls we can delete this code:

func traverseAndReplaceIntegerNodesWithIntegerNodes(node *ast.Node, newType reflect.Type) {
	switch (*node).(type) {
	case *ast.IntegerNode:
		(*node).SetType(newType)
	case *ast.UnaryNode:
		(*node).SetType(newType)
		unaryNode := (*node).(*ast.UnaryNode)
		traverseAndReplaceIntegerNodesWithIntegerNodes(&unaryNode.Node, newType)
	case *ast.BinaryNode:
		// TODO: Binary node return type is dependent on the type of the operands. We can't just change the type of the node.
		binaryNode := (*node).(*ast.BinaryNode)
		switch binaryNode.Operator {
		case "+", "-", "*":
			traverseAndReplaceIntegerNodesWithIntegerNodes(&binaryNode.Left, newType)
			traverseAndReplaceIntegerNodesWithIntegerNodes(&binaryNode.Right, newType)
		}
	}
}

And replace it with implicit added calls to int*.

NOTE
We should check for overflows on conversion in checkers!

[jippi]

If you haven't looking into go-cty, then I can 10/10 recommend it for a pseudo-type system like this - it's really flexible and powerful :)

[antonmedv]

Although cty looks interesting, I believe we better stick with native Go types. Also, I'm not sure how cty can help in case of:

func(123)

In func takes uint32 param.