Rename AsyncCoroutineKind to CoroutineSource

similar to how we have `MatchSource`, it explains where the desugaring came from.

compiler/rustc_hir/src/hir.rs

@@ -1511,7 +1511,7 @@ impl<'hir> Body<'hir> {
 #[derive(HashStable_Generic, Encodable, Decodable)]
 pub enum CoroutineKind {
     /// An explicit `async` block or the body of an async function.
-    Async(AsyncCoroutineKind),
+    Async(CoroutineSource),
 
     /// A coroutine literal created via a `yield` inside a closure.
     Coroutine,
@@ -1535,40 +1535,40 @@ impl CoroutineKind {
     }
 }
 
-/// In the case of a coroutine created as part of an async construct,
-/// which kind of async construct caused it to be created?
+/// In the case of a coroutine created as part of an async/gen construct,
+/// which kind of async/gen construct caused it to be created?
 ///
 /// This helps error messages but is also used to drive coercions in
 /// type-checking (see #60424).
 #[derive(Clone, PartialEq, Eq, Hash, Debug, Copy)]
 #[derive(HashStable_Generic, Encodable, Decodable)]
-pub enum AsyncCoroutineKind {
-    /// An explicit `async` block written by the user.
+pub enum CoroutineSource {
+    /// An explicit `async`/`gen` block written by the user.
     Block,
 
-    /// An explicit `async` closure written by the user.
+    /// An explicit `async`/`gen` closure written by the user.
     Closure,
 
-    /// The `async` block generated as the body of an async function.
+    /// The `async`/`gen` block generated as the body of an async/gen function.
     Fn,
 }
 
-impl fmt::Display for AsyncCoroutineKind {
+impl fmt::Display for CoroutineSource {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str(match self {
-            AsyncCoroutineKind::Block => "async block",
-            AsyncCoroutineKind::Closure => "async closure body",
-            AsyncCoroutineKind::Fn => "async fn body",
+            CoroutineSource::Block => "async block",
+            CoroutineSource::Closure => "async closure body",
+            CoroutineSource::Fn => "async fn body",
         })
     }
 }
 
-impl AsyncCoroutineKind {
+impl CoroutineSource {
     pub fn descr(&self) -> &'static str {
         match self {
-            AsyncCoroutineKind::Block => "`async` block",
-            AsyncCoroutineKind::Closure => "`async` closure body",
-            AsyncCoroutineKind::Fn => "`async fn` body",
+            CoroutineSource::Block => "`async` block",
+            CoroutineSource::Closure => "`async` closure body",
+            CoroutineSource::Fn => "`async fn` body",
         }
     }
 }