feat(checker): add slice overloads on lists

invalid function calls now return UnknownType even if the function has a return type

examples/01_simple_type_checking/04_complex_types.py

@@ -33,3 +33,5 @@ a = foo[0]
 b = bar[0][1]
 c = bar[0][1][2]  # invalid, not method __getitem__ on Meter
 c = bar[""]  # invalid, wrong index type
+
+d = foo[1:2]

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/checker/builtins.midas

@@ -129,11 +129,11 @@ extend list[T] {
     def __len__: fn () -> int
     // def __iter__: fn () -> Iterator[T]
     def __getitem__: fn (i: int, /) -> T
-    //__getitem__: fn (s: slice, /) -> list[T]
+    def __getitem__: fn (s: slice, /) -> list[T]
     def __setitem__: fn (key: int, value: T, /) -> None
-    //__setitem__: fn (key: slice, value: list[T], /) -> None
+    def __setitem__: fn (key: slice, value: list[T], /) -> None
     def __delitem__: fn (key: int, /) -> None
-    // def __delitem__: fn (key: slice, /) -> None
+    def __delitem__: fn (key: slice, /) -> None
     // def __add__: fn[S <: T] (value: list[S], /) -> list[T]
     def __add__: fn (value: list[T], /) -> list[T]
     def __iadd__: fn (value: list[T], /) -> list[T]

midas/checker/builtins.py

@@ -29,6 +29,7 @@ def define_builtins(reg: TypesRegistry):
     int = reg.define_type("int", BaseType(name="int"))
     float = reg.define_type("float", BaseType(name="float"))
     str = reg.define_type("str", BaseType(name="str"))
+    slice = reg.define_type("slice", BaseType(name="slice"))
 
     list = reg.define_type(
         "list",

midas/checker/python.py

@@ -507,6 +507,9 @@ class PythonTyper(
             expr.location, operation, [(expr.index, index)], {}
         )
 
+    def visit_slice_expr(self, expr: p.SliceExpr) -> Type:
+        return self.types.get_type("slice")
+
     def visit_base_type(self, node: p.BaseType) -> Type:
         base: Type
         try:
@@ -661,9 +664,10 @@ class PythonTyper(
 
         # No match -> invalid call
         if n_candidates == 0:
+            overloads_str: str = ", ".join(map(str, overloads))
             self.reporter.error(
                 location,
-                f"No matching overload in {overloads} {for_args}",
+                f"No matching overload in [{overloads_str}] {for_args}",
             )
             return None
 

midas/checker/resolver.py

@@ -200,3 +200,11 @@ class Resolver(p.Stmt.Visitor[None], p.Expr.Visitor[None]):
     def visit_subscript_expr(self, expr: p.SubscriptExpr) -> None:
         self.resolve(expr.object)
         self.resolve(expr.index)
+
+    def visit_slice_expr(self, expr: p.SliceExpr) -> None:
+        if expr.lower is not None:
+            self.resolve(expr.lower)
+        if expr.upper is not None:
+            self.resolve(expr.upper)
+        if expr.step is not None:
+            self.resolve(expr.step)

midas/checker/types.py

@@ -164,6 +164,14 @@ def substitute_typevars(type: Type, substitutions: dict[str, Type]) -> Type:
                 returns=substitute_typevars(returns, substitutions),
             )
 
+        case OverloadedFunction(overloads=overloads):
+            return OverloadedFunction(
+                overloads=[
+                    substitute_typevars(overload, substitutions)
+                    for overload in overloads
+                ]
+            )
+
         case ComplexType(members=members):
             members2: dict[str, Type] = {
                 name: substitute_typevars(prop, substitutions)

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/cases/checker/01_simple_types.py.ref.json

@@ -1,4 +1,19 @@
 {
-  "diagnostics": [],
+  "diagnostics": [
+    {
+      "type": "Warning",
+      "location": {
+        "start": [
+          6,
+          4
+        ],
+        "end": [
+          13,
+          5
+        ]
+      },
+      "message": "FrameType not yet supported"
+    }
+  ],
   "judgments": []
 }

tests/cases/checker/03_functions.py.ref.json

@@ -326,9 +326,7 @@
         "arguments": [],
         "keywords": {}
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     },
     {
       "location": {
@@ -407,9 +405,7 @@
         ],
         "keywords": {}
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     },
     {
       "location": {
@@ -505,9 +501,7 @@
         ],
         "keywords": {}
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     },
     {
       "location": {
@@ -604,9 +598,7 @@
           }
         }
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     },
     {
       "location": {
@@ -719,9 +711,7 @@
         ],
         "keywords": {}
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     },
     {
       "location": {
@@ -835,9 +825,7 @@
           }
         }
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     },
     {
       "location": {
@@ -916,9 +904,7 @@
           }
         }
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     },
     {
       "location": {
@@ -997,9 +983,7 @@
           }
         }
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     },
     {
       "location": {
@@ -1461,9 +1445,7 @@
           }
         }
       },
-      "type": {
+      "type": {}
-        "name": "bool"
-      }
     }
   ]
 }

tests/cases/python-parser/02_custom_types.py.ref.json

@@ -18,6 +18,80 @@
         ]
       }
     },
+    {
+      "_type": "TypeAssign",
+      "name": "lat",
+      "type": {
+        "_type": "BaseType",
+        "base": "Column",
+        "param": {
+          "_type": "BaseType",
+          "base": "GeoLocation",
+          "param": null
+        }
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "lat"
+        }
+      ],
+      "value": {
+        "_type": "GetExpr",
+        "object": {
+          "_type": "SubscriptExpr",
+          "object": {
+            "_type": "VariableExpr",
+            "name": "df"
+          },
+          "index": {
+            "_type": "LiteralExpr",
+            "value": "location"
+          }
+        },
+        "name": "lat"
+      }
+    },
+    {
+      "_type": "TypeAssign",
+      "name": "lon",
+      "type": {
+        "_type": "BaseType",
+        "base": "Column",
+        "param": {
+          "_type": "BaseType",
+          "base": "GeoLocation",
+          "param": null
+        }
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "lon"
+        }
+      ],
+      "value": {
+        "_type": "GetExpr",
+        "object": {
+          "_type": "SubscriptExpr",
+          "object": {
+            "_type": "VariableExpr",
+            "name": "df"
+          },
+          "index": {
+            "_type": "LiteralExpr",
+            "value": "location"
+          }
+        },
+        "name": "lon"
+      }
+    },
     {
       "_type": "ExpressionStmt",
       "expr": {
@@ -33,6 +107,64 @@
         }
       }
     },
+    {
+      "_type": "TypeAssign",
+      "name": "lat1",
+      "type": {
+        "_type": "BaseType",
+        "base": "Latitude",
+        "param": null
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "lat1"
+        }
+      ],
+      "value": {
+        "_type": "SubscriptExpr",
+        "object": {
+          "_type": "VariableExpr",
+          "name": "lat"
+        },
+        "index": {
+          "_type": "LiteralExpr",
+          "value": 0
+        }
+      }
+    },
+    {
+      "_type": "TypeAssign",
+      "name": "lat2",
+      "type": {
+        "_type": "BaseType",
+        "base": "Latitude",
+        "param": null
+      }
+    },
+    {
+      "_type": "AssignStmt",
+      "targets": [
+        {
+          "_type": "VariableExpr",
+          "name": "lat2"
+        }
+      ],
+      "value": {
+        "_type": "SubscriptExpr",
+        "object": {
+          "_type": "VariableExpr",
+          "name": "lat"
+        },
+        "index": {
+          "_type": "LiteralExpr",
+          "value": 1
+        }
+      }
+    },
     {
       "_type": "TypeAssign",
       "name": "lat_diff",

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),
+        }