chore: update examples

examples/01_simple_type_checking/02_simple_types.midas

@@ -1,6 +1,6 @@
-type Meter(float)
+type Meter = float
-type Second(float)
+type Second = float
-type MeterPerSecond(float)
+type MeterPerSecond = float
 
 extend Meter {
     op __add__(Meter) -> Meter

examples/01_simple_type_checking/03_control_flow.py

@@ -4,13 +4,20 @@ def minimum(x: int, y: int):
     else:
         return y
 
+
 a = 15
 b = 72
 c = minimum(a, b)
 
+
 def factorial(n: int) -> int:
     if n <= 1:
         return 1
     return n * factorial(n - 1)
 
+
 category = "Category 1" if a < 10 else "Category 2"
+
+
+def foo() -> None:
+    pass

midas/ast/printer.py

@@ -283,7 +283,7 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str], m.Type.Visitor[str]
     def indented(self, text: str) -> str:
         return " " * (self.level * self.indent) + text
 
-    def print(self, expr: m.Expr | m.Stmt):
+    def print(self, expr: m.Expr | m.Stmt | m.Type) -> str:
         self.level = 0
         return expr.accept(self)
 
@@ -314,13 +314,13 @@ class MidasPrinter(m.Expr.Visitor[str], m.Stmt.Visitor[str], m.Type.Visitor[str]
         for op in stmt.operations:
             res += op.accept(self)
         self.level -= 1
-        res += "\n" + self.indented("}")
+        res += self.indented("}")
         return res
 
     def visit_op_stmt(self, stmt: m.OpStmt):
         operand: str = stmt.operand.accept(self)
         result: str = stmt.result.accept(self)
-        return self.indented(f"op {stmt.name.lexeme}({operand}) -> {result}")
+        return self.indented(f"op {stmt.name.lexeme}({operand}) -> {result}\n")
 
     def visit_predicate_stmt(self, stmt: m.PredicateStmt):
         name: str = stmt.name.lexeme

midas/checker/checker.py

@@ -398,7 +398,16 @@ class Checker(
     def visit_variable_expr(self, expr: p.VariableExpr) -> Type:
         return self.look_up_variable(expr.name, expr) or UnknownType()
 
-    def visit_logical_expr(self, expr: p.LogicalExpr) -> Type: ...
+    def visit_logical_expr(self, expr: p.LogicalExpr) -> Type:
+        left: Type = expr.left.accept(self)
+        right: Type = expr.right.accept(self)
+        # TODO: union type
+        if left != right:
+            self.error(
+                expr.location,
+                f"Operands must be of the same type, left={left} != right={right}",
+            )
+        return left
 
     def visit_set_expr(self, expr: p.SetExpr) -> Type: ...
 

midas/cli/highlight.css

@@ -53,5 +53,6 @@ span {
 
     &.keyword {
         color: rgb(211, 72, 9);
+        pointer-events: none;
     }
 }

midas/cli/highlighter.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
+from dataclasses import dataclass
 from pathlib import Path
 from typing import Generic, Optional, Protocol, TextIO, TypeVar
 
@@ -8,6 +9,7 @@ import midas.ast.midas as m
 import midas.ast.python as p
 from midas.ast.location import Location
 from midas.checker.diagnostic import Diagnostic
+from midas.lexer.token import Token
 
 H = TypeVar("H", bound="Highlighter", contravariant=True)
 
@@ -22,6 +24,15 @@ class Locatable(Protocol):
     def location(self) -> Optional[Location]: ...
 
 
+@dataclass(frozen=True)
+class LocatableToken:
+    token: Token
+
+    @property
+    def location(self) -> Location:
+        return self.token.get_location()
+
+
 class Highlighter(ABC):
     BASE_CSS_PATH: Path = Path(__file__).parent / "highlight.css"
     EXTRA_CSS_PATH: Optional[Path] = None
@@ -206,34 +217,22 @@ class PythonHighlighter(
     def visit_ternary_expr(self, expr: p.TernaryExpr) -> None: ...
 
 
-class MidasHighlighter(Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None]):
+class MidasHighlighter(
+    Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None], m.Type.Visitor[None]
+):
     EXTRA_CSS_PATH: Optional[Path] = Path(__file__).parent / "hl_midas.css"
 
     def highlight(self, node: Highlightable[MidasHighlighter]):
         node.accept(self)
 
-    def visit_simple_type_stmt(self, stmt: m.SimpleTypeStmt) -> None:
+    def visit_type_stmt(self, stmt: m.TypeStmt) -> None:
-        self.wrap(stmt, "simple-type")
+        self.wrap(stmt, "type-stmt")
-        if stmt.template is not None:
+        self.wrap(LocatableToken(stmt.name), "type-name")
-            stmt.template.accept(self)
+        stmt.type.accept(self)
-        stmt.base.accept(self)
-        if stmt.constraint is not None:
-            self.wrap(stmt.constraint, "constraint")
-            stmt.constraint.accept(self)
-
-    def visit_complex_type_stmt(self, stmt: m.ComplexTypeStmt) -> None:
-        self.wrap(stmt, "complex-type")
-        if stmt.template is not None:
-            stmt.template.accept(self)
-        for prop in stmt.properties:
-            prop.accept(self)
 
     def visit_property_stmt(self, stmt: m.PropertyStmt) -> None:
         self.wrap(stmt, "property")
         stmt.type.accept(self)
-        if stmt.constraint is not None:
-            self.wrap(stmt.constraint, "constraint")
-            stmt.constraint.accept(self)
 
     def visit_extend_stmt(self, stmt: m.ExtendStmt) -> None:
         self.wrap(stmt, "extend")
@@ -243,17 +242,16 @@ class MidasHighlighter(Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None]):
 
     def visit_op_stmt(self, stmt: m.OpStmt) -> None:
         self.wrap(stmt, "op")
+        self.wrap(LocatableToken(stmt.name), "op-name")
         stmt.operand.accept(self)
         stmt.result.accept(self)
 
     def visit_predicate_stmt(self, stmt: m.PredicateStmt) -> None:
         self.wrap(stmt, "predicate")
+        self.wrap(LocatableToken(stmt.name), "predicate-name")
         stmt.type.accept(self)
         stmt.condition.accept(self)
 
-    def visit_simple_type_expr(self, expr: m.SimpleTypeExpr) -> None:
-        self.wrap(expr, "simple-type-expr")
-
     def visit_logical_expr(self, expr: m.LogicalExpr) -> None:
         self.wrap(expr, "logical-expr")
         expr.left.accept(self)
@@ -282,14 +280,29 @@ class MidasHighlighter(Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None]):
 
     def visit_wildcard_expr(self, expr: m.WildcardExpr) -> None: ...
 
-    def visit_template_expr(self, expr: m.TemplateExpr) -> None:
+    def visit_named_type(self, type: m.NamedType) -> None:
-        self.wrap(expr, "template")
+        self.wrap(type, "named-type")
-        expr.type.accept(self)
 
-    def visit_type_expr(self, expr: m.TypeExpr) -> None:
+    def visit_generic_type(self, type: m.GenericType) -> None:
-        self.wrap(expr, "type")
+        self.wrap(type, "generic-type")
-        if expr.template is not None:
+        type.type.accept(self)
-            expr.template.accept(self)
+        for param in type.params:
+            param.accept(self)
+
+    def visit_constraint_type(self, type: m.ConstraintType) -> None:
+        self.wrap(type, "constraint-type")
+        type.type.accept(self)
+        type.constraint.accept(self)
+
+    def visit_union_type(self, type: m.UnionType) -> None:
+        self.wrap(type, "union-type")
+        for type_ in type.types:
+            type_.accept(self)
+
+    def visit_complex_type(self, type: m.ComplexType) -> None:
+        self.wrap(type, "complex-type")
+        for prop in type.properties:
+            prop.accept(self)
 
 
 class DiagnosticsHighlighter(Highlighter):

midas/cli/hl_midas.css

@@ -5,12 +5,12 @@ span {
         font-style: italic;
     }
 
-    &.simple-type {
+    &.named-type,
-        --col: 108, 233, 108;
+    &.generic-type,
-    }
+    &.constraint-type,
-
+    &.union-type,
     &.complex-type {
-        --col: 233, 206, 108;
+        --col: 150, 150, 150;
     }
 
     &.constraint {
@@ -33,10 +33,6 @@ span {
         --col: 193, 108, 233;
     }
 
-    &.simple-type-expr {
-        --col: 150, 150, 150;
-    }
-
     &.logical-expr,
     &.binary-expr,
     &.unary-expr,
@@ -48,7 +44,9 @@ span {
         --col: 163, 117, 71;
     }
 
-    &.type {
+    &.type-name,
+    &.op-name,
+    &.predicate-name {
         --col: 200, 200, 200;
         font-weight: bold;
     }

midas/cli/main.py

@@ -1,7 +1,6 @@
 import ast
 import json
 import logging
-from dataclasses import dataclass
 from pathlib import Path
 from typing import Optional, TextIO, get_args
 
@@ -9,14 +8,14 @@ import click
 
 import midas.ast.midas as m
 import midas.ast.python as p
-from midas.ast.location import Location
+from midas.ast.printer import MidasAstPrinter, MidasPrinter, PythonAstPrinter
-from midas.ast.printer import MidasAstPrinter, PythonAstPrinter
 from midas.checker.checker import Checker
 from midas.checker.diagnostic import Diagnostic
 from midas.checker.types import Type
 from midas.cli.highlighter import (
     DiagnosticsHighlighter,
     Highlighter,
+    LocatableToken,
     MidasHighlighter,
     PythonHighlighter,
 )
@@ -142,14 +141,6 @@ def highlight_midas(source: str, path: str) -> Highlighter:
     for err in parser.errors:
         print(err.get_report())
 
-    @dataclass(frozen=True)
-    class LocatableToken:
-        token: Token
-
-        @property
-        def location(self) -> Location:
-            return self.token.get_location()
-
     for stmt in stmts:
         highlighter.highlight(stmt)
     for token in tokens:
@@ -176,5 +167,21 @@ def highlight(output: TextIO, file: TextIO):
     highlighter.dump(output)
 
 
+@midas.command()
+@click.option("-o", "--output", type=click.File("w"), default="-")
+@click.argument("file", type=click.File("r"))
+def format(output: TextIO, file: TextIO):
+    source: str = file.read()
+    printer = MidasPrinter()
+    lexer = MidasLexer(source, file=file.name)
+    tokens: list[Token] = lexer.process()
+    parser = MidasParser(tokens)
+    stmts: list[m.Stmt] = parser.parse()
+    for err in parser.errors:
+        print(err.get_report())
+    for stmt in stmts:
+        output.write(printer.print(stmt) + "\n")
+
+
 if __name__ == "__main__":
     midas()

midas/parser/python.py

@@ -87,6 +87,9 @@ class PythonParser:
             case ast.If():
                 return self.parse_if(node)
 
+            case ast.Pass():
+                return None
+
             case _:
                 print(f"Unsupported statement: {ast.unparse(node)}")
                 return None
@@ -311,6 +314,13 @@ class PythonParser:
                             constraint=right_expr,
                         )
 
+            case ast.Constant(value=None):
+                return BaseType(
+                    location=loc,
+                    base="None",
+                    param=None,
+                )
+
             case _:
                 raise UnsupportedSyntaxError(type_expr)
 

midas/resolver/midas.py

@@ -2,6 +2,7 @@ from typing import Optional
 
 import midas.ast.midas as m
 from midas.checker.types import (
+    AliasType,
     Type,
     UnionType,
     UnknownType,
@@ -103,7 +104,8 @@ class MidasResolver(m.Stmt.Visitor[None], m.Expr.Visitor[None], m.Type.Visitor[T
         for param in stmt.params:
             if param.bound is not None:
                 param.bound.accept(self)
-        self.define_type(stmt.name.lexeme, type)
+        name: str = stmt.name.lexeme
+        self.define_type(name, AliasType(name=name, type=type))
 
     def visit_property_stmt(self, stmt: m.PropertyStmt) -> None: ...
 

tests/cases/checker/04_custom_types.midas

@@ -1,6 +1,6 @@
-type Meter(float)
+type Meter = float
-type Second(float)
+type Second = float
-type MeterPerSecond(float)
+type MeterPerSecond = float
 
 extend Meter {
     op __add__(Meter) -> Meter

tests/cases/midas-parser/01_simple_types.midas

@@ -1,15 +1,15 @@
 // Simple custom type derived from float
-type Custom(float)
+type Custom = float
 
 // Simple custom types with constraints
-type Latitude(float) where (-90 <= _ <= 90)
+type Latitude = float where (-90 <= _ <= 90)
-type Longitude(float) where (-180 <= _ <= 180)
+type Longitude = float where (-180 <= _ <= 180)
 
 // Generic custom type (a Difference of T is derived from T, e.g. a difference of floats is a float
-type Difference[T](T)
+type Difference[T] = T
 
 // Complex custom type, containing two values accessible through properties
-type GeoLocation {
+type GeoLocation = {
     lat: Latitude
     lon: Longitude
 }
@@ -24,7 +24,7 @@ extend GeoLocation {
 
 // For complex generics, you need to specify how the genericity the properties
 // are handled
-type Difference[GeoLocation] {
+type Difference[GeoLocation] = {
     lat: Difference[Latitude]
     lon: Difference[Longitude]
 }
@@ -44,11 +44,11 @@ predicate StrictlyPositive(v: float) = v > 0
 predicate Equatorial(loc: GeoLocation) = (-10 <= loc.lat <= 10)
 predicate Arctic(loc: GeoLocation) = (loc.lat >= 66)
 
-type Person {
+type Person = {
     name: str
 
     // Property with an inline constraint
-    age: int? where (0 <= _ < 150)
+    age: None | (int where (0 <= _ < 150))
 
     // Property referencing a predicate
     height: float where StrictlyPositive

tests/serializer/midas.py

@@ -2,56 +2,61 @@ from typing import Optional, Sequence
 
 from midas.ast.midas import (
     BinaryExpr,
-    ComplexTypeStmt,
+    ComplexType,
+    ConstraintType,
     Expr,
     ExtendStmt,
+    GenericType,
     GetExpr,
     GroupingExpr,
     LiteralExpr,
     LogicalExpr,
+    NamedType,
     OpStmt,
     PredicateStmt,
     PropertyStmt,
-    SimpleTypeExpr,
-    SimpleTypeStmt,
     Stmt,
-    TemplateExpr,
+    Type,
-    TypeExpr,
+    TypeStmt,
     UnaryExpr,
+    UnionType,
     VariableExpr,
     WildcardExpr,
 )
 
 
-class MidasAstJsonSerializer(Stmt.Visitor[dict], Expr.Visitor[dict]):
+class MidasAstJsonSerializer(
+    Stmt.Visitor[dict], Expr.Visitor[dict], Type.Visitor[dict]
+):
     """An AST serializer which produces a JSON-compatible structure"""
 
     def serialize(self, stmts: list[Stmt]) -> list[dict]:
         return [stmt.accept(self) for stmt in stmts]
 
-    def _serialize_optional(self, element: Optional[Stmt | Expr]) -> Optional[dict]:
+    def _serialize_optional(
+        self, element: Optional[Stmt | Expr | Type]
+    ) -> Optional[dict]:
         if element is None:
             return None
         return element.accept(self)
 
-    def _serialize_list(self, elements: Sequence[Stmt | Expr]) -> list[dict]:
+    def _serialize_list(self, elements: Sequence[Stmt | Expr | Type]) -> list[dict]:
         return [element.accept(self) for element in elements]
 
-    def visit_simple_type_stmt(self, stmt: SimpleTypeStmt) -> dict:
+    def visit_type_stmt(self, stmt: TypeStmt) -> dict:
         return {
-            "_type": "SimpleTypeStmt",
+            "_type": "TypeStmt",
             "name": stmt.name.lexeme,
-            "template": self._serialize_optional(stmt.template),
+            "params": [
-            "base": stmt.base.accept(self),
+                self._serialize_type_stmt_template_param(param) for param in stmt.params
-            "constraint": self._serialize_optional(stmt.constraint),
+            ],
+            "type": stmt.type.accept(self),
         }
 
-    def visit_complex_type_stmt(self, stmt: ComplexTypeStmt) -> dict:
+    def _serialize_type_stmt_template_param(self, param: TypeStmt.Param) -> dict:
         return {
-            "_type": "ComplexTypeStmt",
+            "name": param.name.lexeme,
-            "name": stmt.name.lexeme,
+            "bound": self._serialize_optional(param.bound),
-            "template": self._serialize_optional(stmt.template),
-            "properties": self._serialize_list(stmt.properties),
         }
 
     def visit_property_stmt(self, stmt: PropertyStmt) -> dict:
@@ -59,7 +64,6 @@ class MidasAstJsonSerializer(Stmt.Visitor[dict], Expr.Visitor[dict]):
             "_type": "PropertyStmt",
             "name": stmt.name.lexeme,
             "type": stmt.type.accept(self),
-            "constraint": self._serialize_optional(stmt.constraint),
         }
 
     def visit_extend_stmt(self, stmt: ExtendStmt) -> dict:
@@ -86,13 +90,6 @@ class MidasAstJsonSerializer(Stmt.Visitor[dict], Expr.Visitor[dict]):
             "condition": stmt.condition.accept(self),
         }
 
-    def visit_simple_type_expr(self, expr: SimpleTypeExpr) -> dict:
-        return {
-            "_type": "SimpleTypeExpr",
-            "name": expr.name.lexeme,
-            "optional": expr.optional,
-        }
-
     def visit_logical_expr(self, expr: LogicalExpr) -> dict:
         return {
             "_type": "LogicalExpr",
@@ -144,16 +141,34 @@ class MidasAstJsonSerializer(Stmt.Visitor[dict], Expr.Visitor[dict]):
     def visit_wildcard_expr(self, expr: WildcardExpr) -> dict:
         return {"_type": "WildcardExpr"}
 
-    def visit_template_expr(self, expr: TemplateExpr) -> dict:
+    def visit_named_type(self, type: NamedType) -> dict:
         return {
-            "_type": "TemplateExpr",
+            "_type": "NamedType",
-            "type": expr.type.accept(self),
+            "name": type.name.lexeme,
         }
 
-    def visit_type_expr(self, expr: TypeExpr) -> dict:
+    def visit_generic_type(self, type: GenericType) -> dict:
         return {
-            "_type": "TypeExpr",
+            "_type": "GenericType",
-            "name": expr.name.lexeme,
+            "type": type.type.accept(self),
-            "template": self._serialize_optional(expr.template),
+            "params": self._serialize_list(type.params),
-            "optional": expr.optional,
+        }
+
+    def visit_constraint_type(self, type: ConstraintType) -> dict:
+        return {
+            "_type": "ConstraintType",
+            "type": type.type.accept(self),
+            "constraint": type.constraint.accept(self),
+        }
+
+    def visit_union_type(self, type: UnionType) -> dict:
+        return {
+            "_type": "UnionType",
+            "types": self._serialize_list(type.types),
+        }
+
+    def visit_complex_type(self, type: ComplexType) -> dict:
+        return {
+            "_type": "ComplexType",
+            "properties": self._serialize_list(type.properties),
         }

tests/serializer/python.py

@@ -22,6 +22,7 @@ from midas.ast.python import (
     ReturnStmt,
     SetExpr,
     Stmt,
+    TernaryExpr,
     TypeAssign,
     UnaryExpr,
     VariableExpr,
@@ -245,3 +246,11 @@ class PythonAstJsonSerializer(
             "type": expr.type.accept(self),
             "expr": expr.expr.accept(self),
         }
+
+    def visit_ternary_expr(self, expr: TernaryExpr) -> dict:
+        return {
+            "_type": "TernaryExpr",
+            "test": expr.test.accept(self),
+            "if_true": expr.if_true.accept(self),
+            "if_false": expr.if_false.accept(self),
+        }