Dont diagnose lifetime dependence on BitwiseCopyable & ~Escapable type in Sema

rdar://123870480

Author: meg-gupta

lib/Sema/LifetimeDependence.cpp

@@ -178,12 +178,20 @@ LifetimeDependenceInfo::fromTypeRepr(AbstractFunctionDecl *afd, Type resultType,
       }
     }
 
-    if (ctx.LangOpts.hasFeature(Feature::BitwiseCopyable)) {
-      auto *bitwiseCopyableProtocol =
-          ctx.getProtocol(KnownProtocolKind::BitwiseCopyable);
-      if (bitwiseCopyableProtocol && mod->checkConformance(type, bitwiseCopyableProtocol)) {
-        diags.diagnose(loc, diag::lifetime_dependence_on_bitwise_copyable);
-        return true;
+    // Diagnose when we have lifetime dependence on a type that is
+    // BitwiseCopyable & Escapable.
+    // ~Escapable types are non-trivial in SIL and we should not raise this
+    // error.
+    // TODO: Diagnose ~Escapable types are always non-trivial in SIL.
+    if (type->isEscapable()) {
+      if (ctx.LangOpts.hasFeature(Feature::BitwiseCopyable)) {
+        auto *bitwiseCopyableProtocol =
+            ctx.getProtocol(KnownProtocolKind::BitwiseCopyable);
+        if (bitwiseCopyableProtocol &&
+            mod->checkConformance(type, bitwiseCopyableProtocol)) {
+          diags.diagnose(loc, diag::lifetime_dependence_on_bitwise_copyable);
+          return true;
+        }
       }
     }
 

test/Sema/explicit_lifetime_dependence_specifiers.swift

@@ -1,11 +1,20 @@
 // RUN: %target-typecheck-verify-swift -disable-availability-checking -enable-experimental-feature NonescapableTypes -disable-experimental-parser-round-trip   -enable-experimental-feature NoncopyableGenerics -enable-experimental-feature BitwiseCopyable
 // REQUIRES: asserts
 // REQUIRES: noncopyable_generics
+// REQUIRES: nonescapable_types
 
 struct Container {
   let ptr: UnsafeRawBufferPointer
 }
 
+struct AnotherBufferView : ~Escapable, _BitwiseCopyable {
+  let ptr: UnsafeRawBufferPointer
+  @_unsafeNonescapableResult
+  init(_ ptr: UnsafeRawBufferPointer) {
+    self.ptr = ptr
+  }
+}
+
 struct BufferView : ~Escapable {
   let ptr: UnsafeRawBufferPointer
   @_unsafeNonescapableResult
@@ -16,6 +25,10 @@ struct BufferView : ~Escapable {
     self.ptr = c.ptr
     return self
   }
+  init(_ bv: borrowing AnotherBufferView) -> _borrow(bv) Self {
+    self.ptr = bv.ptr
+    return self
+  }
 }
 
 struct MutableBufferView : ~Escapable, ~Copyable {