Add error/exception handling. Custom error types. Data conversion

grammar/core/base_types.bnf

@@ -1,4 +1,4 @@
-<type> ::= <primitive_type> | <complex_type> | <array_type>
+<type> ::= <primitive_type> | <complex_type> | <array_type> | <error_type>
 
 <primitive_type> ::= "String" | "Integer" | "Decimal" | "Boolean"
 
@@ -6,6 +6,9 @@
 
 <array_type> ::= <type> "<>"
 
-<parameter_type> ::= <type> | "Runnable"
+<parameter_type> ::= <type> 
+                   | "Runnable" 
+                   | <error_type>
+                   | "Any"
 
 <return_type_list> ::= "[" <type> ("," <type>)* "]" | "Runnable"

grammar/declarations/error_declarations.bnf

@@ -0,0 +1,7 @@
+<error_declaration> ::= <identifier> 
+    ["/" <identifier>]? 
+    "{" <error_body>? "}"
+
+<error_body> ::= (<variable_declaration> 
+                | <constant_declaration>
+                | <function_declaration>)*

grammar/declarations/function_declarations.bnf

@@ -1,10 +1,15 @@
 <function_declaration> ::= <accessibility_modifier>"fn" <identifier> 
     <function_signature> 
+    ["fails" "with" <error_type_list>]? 
     "{" <statement>* "}"
 
 <function_signature> ::= "(" <parameter_list>? ")" 
     "->" <return_type_list>
 
+<error_type_list> ::= <error_type> ("," <error_type>)*
+
+<error_type> ::= <identifier> ["/" <identifier>]?
+
 <parameter_list> ::= <required_parameter> 
     ("," <required_parameter>)* 
     [("," <default_parameter>)*]

grammar/operations/control_flow.bnf

@@ -7,6 +7,7 @@
               | <return_statement>
               | <using_statement>
               | <attempt_statement>
+              | <fail_statement>
 
 <assignment_statement> ::= <my_identifier> ".set(" <expression> ")" ";"
 
@@ -35,3 +36,5 @@
 <attempt_statement> ::= <expression> ".attempt" "{" <attempt_handler>* "}"
 
 <attempt_handler> ::= ("ok" | <identifier> | "error") "{" <statement>* "}"
+
+<fail_statement> ::= <my_identifier> ".fail(" <error_type> ["(" <argument_list>? ")"]? ")" ";"

grammar/operations/expressions.bnf

@@ -3,9 +3,12 @@
                | <object_method_call>
                | <constant_expression>
                | <object_instantiation>
+               | <type_conversion_expression>
                | "(" <expression> ")"
                | <lambda_expression>
 
+<type_conversion_expression> ::= <my_identifier> ".as(" <type> ")"
+
 <boolean_expression> ::= 
     <boolean_literal>
     | "(" <boolean_expression> ")"
@@ -28,4 +31,4 @@
     | Boolean.gte(<boolean_expression>, <boolean_expression>)
     | Boolean.lte(<boolean_expression>, <boolean_expression>)
 
-<constant_expression> ::= <my_identifier> ".define(" <literal> ")"
+<constant_expression> ::= <my_identifier> ".define(" <literal> ")"

grammar/operations/method_calls.bnf

@@ -1,8 +1,10 @@
 <object_method_call> ::= <my_identifier> "." <method_name> "(" <argument_list>? ")"
                        | <my_identifier> ".sum()"
+                       | <my_identifier> ".as(" <type> ")"
 
 <method_name> ::= "set"
                 | "define"
+                | "as"
                 | "length" | "reverse" | "split" | "format" 
                 | "search" | "concat" | "replace"
                 | "add" | "subtract" | "multiply" | "divide" | "idivide"