feat(checker): type check dictionaries

midas/checker/builtins.midas

@@ -150,3 +150,32 @@ extend list[T] {
 
     prop __doc__: str
 }
+
+extend dict[K, V] {
+    def copy: fn() -> dict[K, V]
+    def keys: fn() -> list[K]  // TODO: use builtin types
+    def values: fn() -> list[V]  // TODO: use builtin types
+    // def items: fn() -> list[tuple[K, V]]  // TODO: use builtin types
+    
+    // def get: fn(key: K, default: None = None, /) -> V | None
+    def get: fn(key: K, default: V, /) -> V
+    // def get: fn[T](key: K, default: T, /) -> V | T
+    def pop: fn(key: K, /) -> V
+    def pop: fn(key: K, default: V, /) -> V
+    // def pop: fn[T](key: K, default: T, /) -> V | T
+    def __len__: fn() -> int
+    def __getitem__: fn(key: K, /) -> V
+    def __setitem__: fn(key: K, value: V, /) -> None
+    def __delitem__: fn(key: K, /) -> None
+    // def __iter__: fn() -> Iterator[K]
+    def __eq__: fn(value: object, /) -> bool
+    // def __reversed__: fn() -> Iterator[K]
+    
+    def __or__: fn(value: dict[K, V], /) -> dict[K, V]
+    // def __or__: fn[K2, V2](value: dict[K2, V2], /) -> dict[K | K2, V | V2]
+    def __ror__: fn(value: dict[K, V], /) -> dict[K, V]
+    // def __ror__: fn[K2, V2](value: dict[K2, V2], /) -> dict[K | K2, V | V2]
+    // def __ior__: fn(value: SupportsKeysAndGetItem[K, V], /) -> dict[K, V]
+    // def __ior__: fn(value: Iterable[tuple[K, V]], /) -> dict[K, V]
+
+}

midas/checker/builtins.py

@@ -39,3 +39,14 @@ def define_builtins(reg: TypesRegistry):
             body=BaseType(name="list"),
         ),
     )
+    dict = reg.define_type(
+        "dict",
+        GenericType(
+            name="dict",
+            params=[
+                TypeVar(name="K", bound=None),
+                TypeVar(name="V", bound=None),
+            ],
+            body=BaseType(name="dict"),
+        ),
+    )

midas/checker/python.py

@@ -552,6 +552,46 @@ class PythonTyper(
         )
         return self.types.apply_generic(list_type, [UnknownType()])
 
+    def visit_dict_expr(self, expr: p.DictExpr) -> Type:
+        dict_type: Type = self.types.get_type("dict")
+
+        key_types: list[Type] = []
+        value_types: list[Type] = []
+        for key, value in zip(expr.keys, expr.values):
+            if key is None:
+                self.reporter.warning(
+                    value.location, "Dictionary unpacking not supported"
+                )
+                continue
+            key_types.append(self.type_of(key))
+            value_types.append(self.type_of(value))
+
+        key_types = self.types.reduce_types(key_types)
+        value_types = self.types.reduce_types(value_types)
+
+        if len(key_types) == 0 or len(value_types) == 0:
+            return dict_type
+
+        key_type: Type = UnknownType()
+        value_type: Type = UnknownType()
+
+        if len(key_types) == 1:
+            key_type = key_types[0]
+        else:
+            self.reporter.error(
+                expr.location,
+                f"Heterogeneous dict keys: {key_types}",
+            )
+
+        if len(value_types) == 1:
+            value_type = value_types[0]
+        else:
+            self.reporter.error(
+                expr.location,
+                f"Heterogeneous dict values: {value_types}",
+            )
+        return self.types.apply_generic(dict_type, [key_type, value_type])
+
     def visit_subscript_expr(self, expr: p.SubscriptExpr) -> Type:
         object: Type = self.type_of(expr.object)
         operation: Optional[Type] = self.types.lookup_member(object, "__getitem__")

midas/checker/resolver.py

@@ -213,6 +213,13 @@ class Resolver(p.Stmt.Visitor[None], p.Expr.Visitor[None]):
         for item in expr.items:
             self.resolve(item)
 
+    def visit_dict_expr(self, expr: p.DictExpr) -> None:
+        for key in expr.keys:
+            if key is not None:
+                self.resolve(key)
+        for value in expr.values:
+            self.resolve(value)
+
     def visit_subscript_expr(self, expr: p.SubscriptExpr) -> None:
         self.resolve(expr.object)
         self.resolve(expr.index)

midas/generator/generator.py

@@ -4,8 +4,8 @@ from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Optional
 
-from midas.ast.location import Location
 import midas.ast.python as p
+from midas.ast.location import Location
 from midas.checker.types import (
     AliasType,
     AppliedType,
@@ -139,6 +139,12 @@ class Generator(p.Stmt.Visitor[ast.stmt], p.Expr.Visitor[ast.expr]):
             elts=[item.accept(self) for item in expr.items],
         )
 
+    def visit_dict_expr(self, expr: p.DictExpr) -> ast.expr:
+        return ast.Dict(
+            keys=[key.accept(self) if key is not None else None for key in expr.keys],
+            values=[value.accept(self) for value in expr.values],
+        )
+
     def visit_subscript_expr(self, expr: p.SubscriptExpr) -> ast.expr:
         return ast.Subscript(
             value=expr.object.accept(self),