Remove coroutine info when building coroutine drop body

compiler/rustc_middle/src/mir/mod.rs

@@ -244,18 +244,23 @@ impl<'tcx> MirSource<'tcx> {
     }
 }
 
+/// Additional information carried by a MIR body when it is lowered from a coroutine.
+/// This information is modified as it is lowered during the `StateTransform` MIR pass,
+/// so not all fields will be active at a given time. For example, the `yield_ty` is
+/// taken out of the field after yields are turned into returns, and the `coroutine_drop`
+/// body is only populated after the state transform pass.
 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)]
 pub struct CoroutineInfo<'tcx> {
-    /// The yield type of the function, if it is a coroutine.
+    /// The yield type of the function. This field is removed after the state transform pass.
     pub yield_ty: Option<Ty<'tcx>>,
 
-    /// The resume type of the function, if it is a coroutine.
+    /// The resume type of the function. This field is removed after the state transform pass.
     pub resume_ty: Option<Ty<'tcx>>,
 
-    /// Coroutine drop glue.
+    /// Coroutine drop glue. This field is populated after the state transform pass.
     pub coroutine_drop: Option<Body<'tcx>>,
 
-    /// The layout of a coroutine. Produced by the state transformation.
+    /// The layout of a coroutine. This field is populated after the state transform pass.
     pub coroutine_layout: Option<CoroutineLayout<'tcx>>,
 
     /// If this is a coroutine then record the type of source expression that caused this coroutine
@@ -303,6 +308,12 @@ pub struct Body<'tcx> {
     /// and used for debuginfo. Indexed by a `SourceScope`.
     pub source_scopes: IndexVec<SourceScope, SourceScopeData<'tcx>>,
 
+    /// Additional information carried by a MIR body when it is lowered from a coroutine.
+    ///
+    /// Note that the coroutine drop shim, any promoted consts, and other synthetic MIR
+    /// bodies that come from processing a coroutine body are not typically coroutines
+    /// themselves, and should probably set this to `None` to avoid carrying redundant
+    /// information.
     pub coroutine: Option<Box<CoroutineInfo<'tcx>>>,
 
     /// Declarations of locals.

compiler/rustc_mir_transform/src/coroutine.rs

@@ -1231,7 +1231,12 @@ fn create_coroutine_drop_shim<'tcx>(
     drop_clean: BasicBlock,
 ) -> Body<'tcx> {
     let mut body = body.clone();
-    body.arg_count = 1; // make sure the resume argument is not included here
+    // Take the coroutine info out of the body, since the drop shim is
+    // not a coroutine body itself; it just has its drop built out of it.
+    let _ = body.coroutine.take();
+    // Make sure the resume argument is not included here, since we're
+    // building a body for `drop_in_place`.
+    body.arg_count = 1;
 
     let source_info = SourceInfo::outermost(body.span);
 

tests/mir-opt/coroutine_drop_cleanup.main-{closure#0}.coroutine_drop.0.panic-abort.mir

@@ -1,25 +1,4 @@
 // MIR for `main::{closure#0}` 0 coroutine_drop
-/* coroutine_layout = CoroutineLayout {
-    field_tys: {
-        _0: CoroutineSavedTy {
-            ty: std::string::String,
-            source_info: SourceInfo {
-                span: $DIR/coroutine_drop_cleanup.rs:12:13: 12:15 (#0),
-                scope: scope[0],
-            },
-            ignore_for_traits: false,
-        },
-    },
-    variant_fields: {
-        Unresumed(0): [],
-        Returned (1): [],
-        Panicked (2): [],
-        Suspend0 (3): [_0],
-    },
-    storage_conflicts: BitMatrix(1x1) {
-        (_0, _0),
-    },
-} */
 
 fn main::{closure#0}(_1: *mut {coroutine@$DIR/coroutine_drop_cleanup.rs:11:15: 11:17}) -> () {
     let mut _0: ();

tests/mir-opt/coroutine_drop_cleanup.main-{closure#0}.coroutine_drop.0.panic-unwind.mir

@@ -1,25 +1,4 @@
 // MIR for `main::{closure#0}` 0 coroutine_drop
-/* coroutine_layout = CoroutineLayout {
-    field_tys: {
-        _0: CoroutineSavedTy {
-            ty: std::string::String,
-            source_info: SourceInfo {
-                span: $DIR/coroutine_drop_cleanup.rs:12:13: 12:15 (#0),
-                scope: scope[0],
-            },
-            ignore_for_traits: false,
-        },
-    },
-    variant_fields: {
-        Unresumed(0): [],
-        Returned (1): [],
-        Panicked (2): [],
-        Suspend0 (3): [_0],
-    },
-    storage_conflicts: BitMatrix(1x1) {
-        (_0, _0),
-    },
-} */
 
 fn main::{closure#0}(_1: *mut {coroutine@$DIR/coroutine_drop_cleanup.rs:11:15: 11:17}) -> () {
     let mut _0: ();