Merge pull request #75512 from atrick/fix-empty-type

SwiftCompilerSources: use Type.isVoid instead of Type.isEmpty

Author: atrick

SwiftCompilerSources/Sources/SIL/ApplySite.swift

@@ -301,7 +301,7 @@ extension FullApplySite {
       beginApply.yieldedValues.forEach { values.push($0) }
     } else {
       let result = singleDirectResult!
-      if !result.type.isEmpty(in: parentFunction) {
+      if !result.type.isVoid {
         values.push(result)
       }
     }

SwiftCompilerSources/Sources/SIL/Type.swift

@@ -95,6 +95,10 @@ public struct Type : CustomStringConvertible, NoReflectionChildren {
     bridged.isExactSuperclassOf(type.bridged)
   }
 
+  public var isVoid: Bool {
+    bridged.isVoid()
+  }
+
   public func isEmpty(in function: Function) -> Bool {
     bridged.isEmpty(function.bridged)
   }

include/swift/SIL/SILBridging.h

@@ -405,6 +405,7 @@ struct BridgedType {
   BRIDGED_INLINE bool containsNoEscapeFunction() const;
   BRIDGED_INLINE bool isThickFunction() const;
   BRIDGED_INLINE bool isAsyncFunction() const;
+  BRIDGED_INLINE bool isVoid() const;
   BRIDGED_INLINE bool isEmpty(BridgedFunction f) const;
   BRIDGED_INLINE TraitResult canBeClass() const;
   BRIDGED_INLINE bool isMoveOnly() const;

include/swift/SIL/SILBridgingImpl.h

@@ -316,6 +316,10 @@ bool BridgedType::isAsyncFunction() const {
   return unbridged().isAsyncFunction();
 }
 
+bool BridgedType::isVoid() const {
+  return unbridged().isVoid();
+}
+
 bool BridgedType::isEmpty(BridgedFunction f) const {
   return unbridged().isEmpty(*f.getFunction());
 }

test/SILOptimizer/lifetime_dependence/lifetime_dependence_borrow_fail.swift

@@ -29,8 +29,17 @@ struct NC : ~Copyable {
   borrowing func getBV() -> dependsOn(self) BV {
     BV(p, i)
   }
+
+  borrowing func getEmpty() -> Empty {
+    Empty()
+  }
 }
 
+// Test dependencies on an empty struct.
+public struct Empty: ~Escapable {}
+
+func use(e: Empty) {}
+
 struct NE : ~Escapable {
   let p: UnsafeRawPointer
   let i: Int
@@ -68,3 +77,12 @@ let nc = NC(ptr, 0) // expected-error {{lifetime-dependent variable 'nc' escapes
 func bv_global(dummy: BV) -> BV {
   nc.getBV()
 } // expected-note {{this use causes the lifetime-dependent value to escape}}
+
+func testEmpty(nc: consuming NC) {
+  var e: Empty // expected-error {{lifetime-dependent variable 'e' escapes its scope}}
+  do {
+    let inner = nc // expected-note {{it depends on the lifetime of variable 'inner'}}
+    e = inner.getEmpty()
+  }
+  use(e: e) // expected-note {{this use of the lifetime-dependent value is out of scope}}
+}