static type checking

[michal-kapala]

Important LSP server feature that would allow it to return implicit conversion warnings or type errors without evaluation:

• unknown return type needed for some functions (such as RunScript) and globals
• error and warning collection
• identifier type info collection from AST nodes (variables, function names from call expressions)
• expression type inference
  • assignments
  • literals
  • local identifiers
  • global/system identifiers
  • binary expressions
  • unary expressions
  • member expressions (dont seem possible without static types of arrays/dicts)
  • block expressions
  • calls (per-function validation)

Challenges

• signature selection and call argument type validation
• ArgumentList - the args are uninitialized local identifiers (regular names or _1, _2, _3 etc.), the call should update the env and AST types to unknown
• default script arg identifier support #14
• node return type, impossible to guess without a schema (unknown)
• type return type, sometimes solved by call arg types, sometimes remains ambiguous
• arg list length validation to be moved off parser (runtime/typechecker switch needed)