Add MutatingUseContext::Yield

...emulating `MutatingUseContext::Call`

src/librustc_codegen_ssa/mir/analyze.rs

@@ -269,7 +269,8 @@ impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
 
     fn visit_local(&mut self, &local: &mir::Local, context: PlaceContext, location: Location) {
         match context {
-            PlaceContext::MutatingUse(MutatingUseContext::Call) => {
+            PlaceContext::MutatingUse(MutatingUseContext::Call)
+            | PlaceContext::MutatingUse(MutatingUseContext::Yield) => {
                 self.assign(local, location);
             }
 

src/librustc_middle/mir/visit.rs

@@ -510,7 +510,7 @@ macro_rules! make_mir_visitor {
                         self.visit_operand(value, source_location);
                         self.visit_place(
                             resume_arg,
-                            PlaceContext::MutatingUse(MutatingUseContext::Store),
+                            PlaceContext::MutatingUse(MutatingUseContext::Yield),
                             source_location,
                         );
                     }
@@ -1052,6 +1052,8 @@ pub enum MutatingUseContext {
     AsmOutput,
     /// Destination of a call.
     Call,
+    /// Destination of a yield.
+    Yield,
     /// Being dropped.
     Drop,
     /// Mutable borrow.

src/librustc_mir/util/liveness.rs

@@ -133,6 +133,7 @@ pub fn categorize(context: PlaceContext) -> Option<DefUse> {
         // the def in call only to the input from the success
         // path and not the unwind path. -nmatsakis
         PlaceContext::MutatingUse(MutatingUseContext::Call) |
+        PlaceContext::MutatingUse(MutatingUseContext::Yield) |
 
         // Storage live and storage dead aren't proper defines, but we can ignore
         // values that come before them.