Rename Red Knot (#17820)

crates/ty_python_semantic/resources/mdtest/subscript/string.md

@@ -0,0 +1,92 @@
+# String subscripts
+
+## Indexing
+
+```py
+s = "abcde"
+
+reveal_type(s[0])  # revealed: Literal["a"]
+reveal_type(s[1])  # revealed: Literal["b"]
+reveal_type(s[-1])  # revealed: Literal["e"]
+reveal_type(s[-2])  # revealed: Literal["d"]
+
+reveal_type(s[False])  # revealed: Literal["a"]
+reveal_type(s[True])  # revealed: Literal["b"]
+
+a = s[8]  # error: [index-out-of-bounds] "Index 8 is out of bounds for string `Literal["abcde"]` with length 5"
+reveal_type(a)  # revealed: Unknown
+
+b = s[-8]  # error: [index-out-of-bounds] "Index -8 is out of bounds for string `Literal["abcde"]` with length 5"
+reveal_type(b)  # revealed: Unknown
+
+def _(n: int):
+    a = "abcde"[n]
+    reveal_type(a)  # revealed: LiteralString
+```
+
+## Slices
+
+```py
+def _(m: int, n: int, s2: str):
+    s = "abcde"
+
+    reveal_type(s[0:0])  # revealed: Literal[""]
+    reveal_type(s[0:1])  # revealed: Literal["a"]
+    reveal_type(s[0:2])  # revealed: Literal["ab"]
+    reveal_type(s[0:5])  # revealed: Literal["abcde"]
+    reveal_type(s[0:6])  # revealed: Literal["abcde"]
+    reveal_type(s[1:3])  # revealed: Literal["bc"]
+
+    reveal_type(s[-3:5])  # revealed: Literal["cde"]
+    reveal_type(s[-4:-2])  # revealed: Literal["bc"]
+    reveal_type(s[-10:10])  # revealed: Literal["abcde"]
+
+    reveal_type(s[0:])  # revealed: Literal["abcde"]
+    reveal_type(s[2:])  # revealed: Literal["cde"]
+    reveal_type(s[5:])  # revealed: Literal[""]
+    reveal_type(s[:2])  # revealed: Literal["ab"]
+    reveal_type(s[:0])  # revealed: Literal[""]
+    reveal_type(s[:2])  # revealed: Literal["ab"]
+    reveal_type(s[:10])  # revealed: Literal["abcde"]
+    reveal_type(s[:])  # revealed: Literal["abcde"]
+
+    reveal_type(s[::-1])  # revealed: Literal["edcba"]
+    reveal_type(s[::2])  # revealed: Literal["ace"]
+    reveal_type(s[-2:-5:-1])  # revealed: Literal["dcb"]
+    reveal_type(s[::-2])  # revealed: Literal["eca"]
+    reveal_type(s[-1::-3])  # revealed: Literal["eb"]
+
+    reveal_type(s[None:2:None])  # revealed: Literal["ab"]
+    reveal_type(s[1:None:1])  # revealed: Literal["bcde"]
+    reveal_type(s[None:None:None])  # revealed: Literal["abcde"]
+
+    start = 1
+    stop = None
+    step = 2
+    reveal_type(s[start:stop:step])  # revealed: Literal["bd"]
+
+    reveal_type(s[False:True])  # revealed: Literal["a"]
+    reveal_type(s[True:3])  # revealed: Literal["bc"]
+
+    s[0:4:0]  # error: [zero-stepsize-in-slice]
+    s[:4:0]  # error: [zero-stepsize-in-slice]
+    s[0::0]  # error: [zero-stepsize-in-slice]
+    s[::0]  # error: [zero-stepsize-in-slice]
+
+    substring1 = s[m:n]
+    reveal_type(substring1)  # revealed: LiteralString
+
+    substring2 = s2[0:5]
+    reveal_type(substring2)  # revealed: str
+```
+
+## Unsupported slice types
+
+```py
+# TODO: It would be great if we raised an error here. This can be done once
+# we have support for overloads and generics, and once typeshed has a more
+# precise annotation for `str.__getitem__`, that makes use of the generic
+# `slice[..]` type. We could then infer `slice[str, str]` here and see that
+# it doesn't match the signature of `str.__getitem__`.
+"foo"["bar":"baz"]
+```