Use __index__ for __getitem__ and __setitem__

When indexing stdlib containers we should accept a generic type that calls
on the  __index__ method to allow types other than Int to be used but
doesn't allow Intable types that should not be used for such purposes
(such as Float)

Signed-off-by: Brian Grenier <grenierb96@gmail.com>

stdlib/src/builtin/int.mojo

@@ -169,7 +169,7 @@ fn int[T: IntableRaising](value: T) raises -> Int:
 @lldb_formatter_wrapping_type
 @value
 @register_passable("trivial")
-struct Int(Intable, Stringable, KeyElement, Boolable):
+struct Int(Intable, Stringable, KeyElement, Boolable, Indexer):
     """This type represents an integer value."""
 
     var value: __mlir_type.index

stdlib/src/builtin/int_literal.mojo

@@ -16,7 +16,7 @@
 @value
 @nonmaterializable(Int)
 @register_passable("trivial")
-struct IntLiteral(Intable, Stringable, Boolable, EqualityComparable):
+struct IntLiteral(Intable, Stringable, Boolable, EqualityComparable, Indexer):
     """This type represents a static integer literal value with
     infinite precision.  They can't be materialized at runtime and
     must be lowered to other integer types (like Int), but allow for

stdlib/src/builtin/range.mojo

@@ -92,8 +92,8 @@ struct _ZeroStartingRange(Sized, ReversibleRange):
         return self.curr
 
     @always_inline("nodebug")
-    fn __getitem__(self, idx: Int) -> Int:
-        return idx
+    fn __getitem__[indexer: Indexer](self, idx: indexer) -> Int:
+        return idx.__index__()
 
     @always_inline("nodebug")
     fn __reversed__(self) -> _StridedRangeIterator:
@@ -121,8 +121,8 @@ struct _SequentialRange(Sized, ReversibleRange):
         return _max(0, self.end - self.start)
 
     @always_inline("nodebug")
-    fn __getitem__(self, idx: Int) -> Int:
-        return self.start + idx
+    fn __getitem__[indexer: Indexer](self, idx: indexer) -> Int:
+        return self.start + idx.__index__()
 
     @always_inline("nodebug")
     fn __reversed__(self) -> _StridedRangeIterator:
@@ -192,8 +192,8 @@ struct _StridedRange(Sized, ReversibleRange):
         return _div_ceil_positive(_abs(self.start - self.end), _abs(self.step))
 
     @always_inline("nodebug")
-    fn __getitem__(self, idx: Int) -> Int:
-        return self.start + idx * self.step
+    fn __getitem__[indexer: Indexer](self, idx: indexer) -> Int:
+        return self.start + idx.__index__() * self.step
 
     @always_inline("nodebug")
     fn __reversed__(self) -> _StridedRangeIterator:

stdlib/src/builtin/simd.mojo

@@ -119,6 +119,7 @@ struct SIMD[type: DType, size: Int = simdwidthof[type]()](
     Stringable,
     Hashable,
     Boolable,
+    Indexer
 ):
     """Represents a small vector that is backed by a hardware vector element.
 
@@ -513,6 +514,11 @@ struct SIMD[type: DType, size: Int = simdwidthof[type]()](
             rebind[Scalar[type]](self).value
         )
 
+    @always_inline("nodebug")
+    fn __index__(self) -> Int:
+        constrained[type.is_integral(), "Expected an integral type"]()
+        return int(self)
+
     @always_inline
     fn __str__(self) -> String:
         """Get the SIMD as a string.

stdlib/src/builtin/value.mojo

@@ -121,3 +121,12 @@ trait StringableCollectionElement(CollectionElement, Stringable):
     """
 
     pass
+
+trait Indexer:
+    fn __index__(self) -> Int:
+        """Return the index value
+
+        Returns:
+            The index value of the object
+        """
+        ...

stdlib/src/collections/vector.mojo

@@ -182,7 +182,7 @@ struct InlinedFixedVector[
         return self.current_size
 
     @always_inline
-    fn __getitem__(self, i: Int) -> type:
+    fn __getitem__[indexer: Indexer](self, i: indexer) -> type:
         """Gets a vector element at the given index.
 
         Args:
@@ -191,12 +191,12 @@ struct InlinedFixedVector[
         Returns:
             The element at the given index.
         """
+        var normalized_idx = i.__index__()
         debug_assert(
-            -self.current_size <= i < self.current_size,
+            -self.current_size <= normalized_idx < self.current_size,
             "index must be within bounds",
         )
-        var normalized_idx = i
-        if i < 0:
+        if normalized_idx < 0:
             normalized_idx += len(self)
 
         if normalized_idx < Self.static_size:
@@ -205,20 +205,21 @@ struct InlinedFixedVector[
         return self.dynamic_data[normalized_idx - Self.static_size]
 
     @always_inline
-    fn __setitem__(inout self, i: Int, value: type):
+    fn __setitem__[indexer: Indexer](inout self, i: indexer, value: type):
         """Sets a vector element at the given index.
 
         Args:
             i: The index of the element.
             value: The value to assign.
         """
+        var normalized_idx = i.__index__()
         debug_assert(
-            -self.current_size <= i < self.current_size,
+            -self.current_size <= normalized_idx < self.current_size,
             "index must be within bounds",
         )
 
-        var normalized_idx = i
-        if i < 0:
+
+        if normalized_idx < 0:
             normalized_idx += len(self)
 
         if normalized_idx < Self.static_size:

stdlib/src/python/object.mojo

@@ -101,7 +101,7 @@ struct _PyIter(Sized):
 
 @register_passable
 struct PythonObject(
-    Intable, Stringable, SizedRaising, Boolable, CollectionElement, KeyElement
+    Intable, Stringable, SizedRaising, Boolable, CollectionElement, KeyElement, Indexer
 ):
     """A Python object."""