Phase 2 of Typing Improvements

[markwpearce]

A second phase of type improvements for Brighterscript

Tasks

• BinaryExpressions and UnaryExpressions should be able to infer resultant types (eg. Integer * Integer => Integer, String + String => String, etc.)

• Change Hover & Completion to use SymbolTable instead of variableDeclarations/callables
  This will complete the refactor to move away from using these lookup tables to unify how a symbol can be discovered/known. When this is done, the concept of VariableDeclarations can be removed from the code.

• Validate function calls for argument type validity

  Function argument equality

  sub main()
      printMessage(1)
      '            ~ Argument of type 'number' is not assignable to parameter of type 'string'
  end sub
  function printMessage(message as string)
      print message
  end function

Phase 3

• Validate assignment expressions for type validity

  AssignmentStatement type equality

  sub main()
      name = "bob"
      name = 1
  end sub
  '      ~ type 'Integer' cannot be assigned to type 'String'

• Add ComponentType that are generated from XML or future Component creation. Members (and member types) could be inferred from the component's fields

• CreateObject() should infer correct type (using data scraped from Roku SceneGraph docs for built in types, or from known components)

• Update ArrayType to allow indexedGet, etc. to infer type. Allow code & validation like:

  function sumArray(numbers as integer[]) as integer
       sum = 0
       for each num in numbers
           sum = sum + num ' num is known to be an integer
       end for
       return sum
   end function
   
   sub addName(nameList as string[])
        nameList.push(3.14) ' validation error --- nameList.push expects string
    end sub

   ```