Split rustc_type_ir to avoid rustc_ast from depending on it

compiler/rustc_ast_ir/src/lib.rs

@@ -0,0 +1,68 @@
+#![cfg_attr(feature = "nightly", feature(rustc_attrs))]
+#![cfg_attr(feature = "nightly", allow(internal_features))]
+
+#[cfg(feature = "nightly")]
+#[macro_use]
+extern crate rustc_macros;
+
+/// The movability of a coroutine / closure literal:
+/// whether a coroutine contains self-references, causing it to be `!Unpin`.
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Copy)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_NoContext))]
+pub enum Movability {
+    /// May contain self-references, `!Unpin`.
+    Static,
+    /// Must not contain self-references, `Unpin`.
+    Movable,
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Copy)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_NoContext))]
+pub enum Mutability {
+    // N.B. Order is deliberate, so that Not < Mut
+    Not,
+    Mut,
+}
+
+impl Mutability {
+    pub fn invert(self) -> Self {
+        match self {
+            Mutability::Mut => Mutability::Not,
+            Mutability::Not => Mutability::Mut,
+        }
+    }
+
+    /// Returns `""` (empty string) or `"mut "` depending on the mutability.
+    pub fn prefix_str(self) -> &'static str {
+        match self {
+            Mutability::Mut => "mut ",
+            Mutability::Not => "",
+        }
+    }
+
+    /// Returns `"&"` or `"&mut "` depending on the mutability.
+    pub fn ref_prefix_str(self) -> &'static str {
+        match self {
+            Mutability::Not => "&",
+            Mutability::Mut => "&mut ",
+        }
+    }
+
+    /// Returns `""` (empty string) or `"mutably "` depending on the mutability.
+    pub fn mutably_str(self) -> &'static str {
+        match self {
+            Mutability::Not => "",
+            Mutability::Mut => "mutably ",
+        }
+    }
+
+    /// Return `true` if self is mutable
+    pub fn is_mut(self) -> bool {
+        matches!(self, Self::Mut)
+    }
+
+    /// Return `true` if self is **not** mutable
+    pub fn is_not(self) -> bool {
+        matches!(self, Self::Not)
+    }
+}