From 276608233e74e1eb478f2af654095bdbd57cd3a6 Mon Sep 17 00:00:00 2001
From: Moreal <dev.moreal@gmail.com>
Date: Sat, 6 Nov 2021 15:46:41 +0900
Subject: [PATCH] Implement `AsMapping` for `PyStr`

---
 vm/src/builtins/pystr.rs | 45 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 40 insertions(+), 5 deletions(-)

diff --git a/vm/src/builtins/pystr.rs b/vm/src/builtins/pystr.rs
index 6327d0bdd..9f0d1d436 100644
--- a/vm/src/builtins/pystr.rs
+++ b/vm/src/builtins/pystr.rs
@@ -7,15 +7,15 @@ use crate::{
     anystr::{self, adjust_indices, AnyStr, AnyStrContainer, AnyStrWrapper},
     format::{FormatSpec, FormatString, FromTemplate},
     function::{ArgIterable, FuncArgs, IntoPyException, IntoPyObject, OptionalArg, OptionalOption},
-    protocol::PyIterReturn,
+    protocol::{PyIterReturn, PyMappingMethods},
     sliceable::PySliceableSequence,
     types::{
-        Comparable, Constructor, Hashable, IterNext, IterNextIterable, Iterable, PyComparisonOp,
-        Unconstructible,
+        AsMapping, Comparable, Constructor, Hashable, IterNext, IterNextIterable, Iterable,
+        PyComparisonOp, Unconstructible,
     },
     utils::Either,
     IdProtocol, ItemProtocol, PyClassDef, PyClassImpl, PyComparisonValue, PyContext, PyObject,
-    PyObjectRef, PyRef, PyResult, PyValue, TypeProtocol, VirtualMachine,
+    PyObjectRef, PyObjectView, PyRef, PyResult, PyValue, TypeProtocol, VirtualMachine,
 };
 use ascii::{AsciiStr, AsciiString};
 use bstr::ByteSlice;
@@ -363,7 +363,10 @@ impl PyStr {
     }
 }
 
-#[pyimpl(flags(BASETYPE), with(Hashable, Comparable, Iterable, Constructor))]
+#[pyimpl(
+    flags(BASETYPE),
+    with(AsMapping, Hashable, Comparable, Iterable, Constructor)
+)]
 impl PyStr {
     #[pymethod(magic)]
     fn add(zelf: PyRef<Self>, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
@@ -1245,6 +1248,38 @@ impl Iterable for PyStr {
     }
 }
 
+impl AsMapping for PyStr {
+    fn as_mapping(_zelf: &PyObjectView<Self>, _vm: &VirtualMachine) -> PyMappingMethods {
+        PyMappingMethods {
+            length: Some(Self::length),
+            subscript: Some(Self::subscript),
+            ass_subscript: None,
+        }
+    }
+
+    #[inline]
+    fn length(zelf: PyObjectRef, vm: &VirtualMachine) -> PyResult<usize> {
+        Self::downcast_ref(&zelf, vm).map(|zelf| Ok(zelf.len()))?
+    }
+
+    #[inline]
+    fn subscript(zelf: PyObjectRef, needle: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        Self::downcast_ref(&zelf, vm)
+            .map(|zelf| zelf.getitem(needle, vm))?
+            .map(|item| item.into_object(vm))
+    }
+
+    #[cold]
+    fn ass_subscript(
+        zelf: PyObjectRef,
+        _needle: PyObjectRef,
+        _value: Option<PyObjectRef>,
+        _vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        unreachable!("ass_subscript not implemented for {}", zelf.class())
+    }
+}
+
 #[derive(FromArgs)]
 struct EncodeArgs {
     #[pyarg(any, default)]