schala/src/schala_lang/type_check.rs

use std::collections::HashMap;
use std::rc::Rc;

use schala_lang::parsing::{AST, Statement, Declaration, Expression, ExpressionType, Operation, TypeAnno};

#[derive(Debug, PartialEq, Eq, Hash)]
struct PathSpecifier {
  name: Rc<String>,
  kind: &'static str,
  constant: bool,
}

struct SymbolTable {
  map: HashMap<PathSpecifier, Expression>,
}

impl SymbolTable {
  fn new() -> SymbolTable {
    SymbolTable { map: HashMap::new() }
  }

  fn add_symbols(&mut self, ast: &AST) {
    use self::Declaration::*;

    for statement in ast.0.iter() {
      match statement {
        &Statement::ExpressionStatement(_) => (),
        &Statement::Declaration(ref d) => {
          match d {
            &FuncDecl { .. } => (),
            &TypeDecl { .. } => (),
            &TypeAlias { .. } => (),
            &Binding {ref name, ref constant, ref expr} => {
              let spec = PathSpecifier {
                name: name.clone(),
                kind: "binding",
                constant: *constant
              };
              let binding_contents = (*expr).clone();
              self.map.insert(spec, binding_contents);
            },
            &Impl { .. } => (),
          }
        }
      }
    }
  }
}

pub struct TypeContext {
  symbol_table: SymbolTable,
}

impl TypeContext {
  pub fn new() -> TypeContext {
    TypeContext { symbol_table: SymbolTable::new() }
  }
  pub fn add_symbols(&mut self, ast: &AST) {
    self.symbol_table.add_symbols(ast)
  }
  pub fn debug_symbol_table(&self) -> String  {
    format!("Symbol table:\n {:?}", self.symbol_table.map)
  }
}

pub struct SchalaType {
}

type TypeCheckResult = Result<SchalaType, String>;

// from Niko's talk
/* fn type_check(expression, expected_ty) -> Ty {
    let ty = bare_type_check(expression, expected_type);
    if ty icompatible with expected_ty {
        try_coerce(expression, ty, expected_ty)
    } else {
      ty
    }
  }

  fn bare_type_check(exprssion, expected_type) -> Ty { ... }
 */
impl TypeContext {
  pub fn type_check(&mut self, ast: &AST) -> TypeCheckResult {
    use self::ExpressionType::*;

    for statement in ast.0.iter() {
      match statement {
        &Statement::Declaration(ref _decl) => {
          return Err(format!("Declarations not supported"));
        },
        &Statement::ExpressionStatement(ref expr) => {
          self.expr_type_check(expr)?;
        }
      }
    }
    Ok(SchalaType { })
  }

  fn expr_type_check(&mut self, expr: &Expression) -> TypeCheckResult {
    use self::ExpressionType::*;

    match (&expr.0, &expr.1) {
      (&IntLiteral(_), &Some(ref t)) => {
        match t {
          &TypeAnno::Singleton { ref name, ref params } if **name == "Int" && params.len() == 0 => (),
          t => return Err(format!("Bad type {:?} for int literal", t)),
        }
      },
      _ => (),
    }
    Ok(SchalaType { })
  }
}