SILGen: Unwrap @moveOnly wrapped values before yielding them.

lib/SILGen/SILGenApply.cpp

@@ -6011,8 +6011,18 @@ void SILGenFunction::emitRawYield(SILLocation loc,
                                   JumpDest unwindDest,
                                   bool isUniqueYield) {
   SmallVector<SILValue, 4> yieldValues;
-  for (auto arg : yieldArgs)
+  for (auto arg : yieldArgs) {
-    yieldValues.push_back(arg.getValue());
+    auto value = arg.getValue();
+    if (value->getType().isMoveOnlyWrapped()) {
+      if (value->getType().isAddress()) {
+        value = B.createMoveOnlyWrapperToCopyableAddr(loc, value);
+      } else {
+        value = B.createGuaranteedMoveOnlyWrapperToCopyableValue(loc, value);
+      }
+    }
+    
+    yieldValues.push_back(value);
+  }
 
   // The normal continuation block.
   auto resumeBB = createBasicBlock();

test/SILGen/yield_borrowing.swift

@@ -0,0 +1,20 @@
+// RUN: %target-swift-emit-silgen -verify %s
+struct Foo {
+    var x: String
+
+    var y: Foo {
+        borrowing _read {
+            yield self
+        }
+    }
+}
+
+struct BigFoo {
+    var x: Any
+
+    var y: BigFoo {
+        borrowing _read {
+            yield self
+        }
+    }
+}

test/SILOptimizer/moveonly_borrowing_switch.swift

@@ -299,10 +299,6 @@ extension List {
         }
     }
 
-/*
-    TODO: type mismatch because of `@moveOnly` wrapper. yield needs to peel it
-    off
-
     var head: Element {
         _read {
             switch self {
@@ -313,7 +309,6 @@ extension List {
             }
         }
     }
-*/
 }
 
 extension ChonkyList {
@@ -335,10 +330,6 @@ extension ChonkyList {
         }
     }
 
-/*
-    TODO: type mismatch because of `@moveOnly` wrapper. yield needs to peel it
-    off
-
     var head: Element {
         _read {
             switch self {
@@ -349,6 +340,5 @@ extension ChonkyList {
             }
         }
     }
-*/
 }