chore: checkpoint before Python removal

vendor/serde_yaml/src/path.rs

@@ -0,0 +1,34 @@
+use std::fmt::{self, Display};
+
+/// Path to the current value in the input, like `dependencies.serde.typo1`.
+#[derive(Copy, Clone)]
+pub enum Path<'a> {
+    Root,
+    Seq { parent: &'a Path<'a>, index: usize },
+    Map { parent: &'a Path<'a>, key: &'a str },
+    Alias { parent: &'a Path<'a> },
+    Unknown { parent: &'a Path<'a> },
+}
+
+impl<'a> Display for Path<'a> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        struct Parent<'a>(&'a Path<'a>);
+
+        impl<'a> Display for Parent<'a> {
+            fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+                match self.0 {
+                    Path::Root => Ok(()),
+                    path => write!(formatter, "{}.", path),
+                }
+            }
+        }
+
+        match self {
+            Path::Root => formatter.write_str("."),
+            Path::Seq { parent, index } => write!(formatter, "{}[{}]", parent, index),
+            Path::Map { parent, key } => write!(formatter, "{}{}", Parent(parent), key),
+            Path::Alias { parent } => write!(formatter, "{}", parent),
+            Path::Unknown { parent } => write!(formatter, "{}?", Parent(parent)),
+        }
+    }
+}