feat(parser): add slice expression

gen/python.py

@@ -148,4 +148,10 @@ class SubscriptExpr:
     index: Expr
 
 
+class SliceExpr:
+    lower: Optional[Expr]
+    upper: Optional[Expr]
+    step: Optional[Expr]
+
+
 ###<

midas/ast/printer.py

@@ -729,3 +729,10 @@ class PythonAstPrinter(
             self._write_line("index", last=True)
             with self._child_level(single=True):
                 expr.index.accept(self)
+
+    def visit_slice_expr(self, expr: p.SliceExpr) -> None:
+        self._write_line("SliceExpr")
+        with self._child_level():
+            self._write_optional_child("lower", expr.lower)
+            self._write_optional_child("upper", expr.upper)
+            self._write_optional_child("step", expr.step, last=True)

midas/ast/python.py

@@ -227,6 +227,9 @@ class Expr(ABC):
         @abstractmethod
         def visit_subscript_expr(self, expr: SubscriptExpr) -> T: ...
 
+        @abstractmethod
+        def visit_slice_expr(self, expr: SliceExpr) -> T: ...
+
 
 @dataclass(frozen=True)
 class BinaryExpr(Expr):
@@ -336,3 +339,13 @@ class SubscriptExpr(Expr):
 
     def accept(self, visitor: Expr.Visitor[T]) -> T:
         return visitor.visit_subscript_expr(self)
+
+
+@dataclass(frozen=True)
+class SliceExpr(Expr):
+    lower: Optional[Expr]
+    upper: Optional[Expr]
+    step: Optional[Expr]
+
+    def accept(self, visitor: Expr.Visitor[T]) -> T:
+        return visitor.visit_slice_expr(self)

midas/cli/highlighter.py

@@ -222,6 +222,14 @@ class PythonHighlighter(
         expr.object.accept(self)
         expr.index.accept(self)
 
+    def visit_slice_expr(self, expr: p.SliceExpr) -> None:
+        if expr.lower is not None:
+            expr.lower.accept(self)
+        if expr.upper is not None:
+            expr.upper.accept(self)
+        if expr.step is not None:
+            expr.step.accept(self)
+
 
 class MidasHighlighter(
     Highlighter, m.Stmt.Visitor[None], m.Expr.Visitor[None], m.Type.Visitor[None]

midas/parser/python.py

@@ -22,6 +22,7 @@ from midas.ast.python import (
     LogicalExpr,
     MidasType,
     ReturnStmt,
+    SliceExpr,
     Stmt,
     SubscriptExpr,
     TernaryExpr,
@@ -431,6 +432,14 @@ class PythonParser:
                     index=self.parse_expr(index),
                 )
 
+            case ast.Slice(lower=lower, upper=upper, step=step):
+                return SliceExpr(
+                    location=location,
+                    lower=self.parse_expr(lower) if lower is not None else None,
+                    upper=self.parse_expr(upper) if upper is not None else None,
+                    step=self.parse_expr(step) if step is not None else None,
+                )
+
             case _:
                 raise UnsupportedSyntaxError(node)
 

tests/serializer/python.py

@@ -21,6 +21,7 @@ from midas.ast.python import (
     LogicalExpr,
     MidasType,
     ReturnStmt,
+    SliceExpr,
     Stmt,
     SubscriptExpr,
     TernaryExpr,
@@ -260,3 +261,11 @@ class PythonAstJsonSerializer(
             "object": expr.object.accept(self),
             "index": expr.index.accept(self),
         }
+
+    def visit_slice_expr(self, expr: SliceExpr) -> dict:
+        return {
+            "_type": "SliceExpr",
+            "lower": self._serialize_optional(expr.lower),
+            "upper": self._serialize_optional(expr.upper),
+            "step": self._serialize_optional(expr.step),
+        }