Implemented runes

src/build/errors/CompileErrors.go

@@ -1,9 +1,11 @@
 package errors
 
 var (
-	InvalidStatement    = &Base{"Invalid statement"}
+	InvalidNumber       = &Base{"Invalid number"}
 	InvalidExpression   = &Base{"Invalid expression"}
-	MissingOperand      = &Base{"Missing operand"}
+	InvalidRune         = &Base{"Invalid rune"}
+	InvalidStatement    = &Base{"Invalid statement"}
 	MissingMainFunction = &Base{"Missing main function"}
+	MissingOperand      = &Base{"Missing operand"}
 	NotImplemented      = &Base{"Not implemented"}
 )

src/build/errors/NumberExceedsBounds.go

@@ -0,0 +1,15 @@
+package errors
+
+import "fmt"
+
+// NumberExceedsBounds error is created when the number doesn't fit into the destination.
+type NumberExceedsBounds struct {
+	Number       int
+	Size         byte
+	ExpectedSize byte
+}
+
+// Error generates the string representation.
+func (err *NumberExceedsBounds) Error() string {
+	return fmt.Sprintf("Number %d needs %d bytes but the maximum is %d bytes", err.Number, err.Size, err.ExpectedSize)
+}