---

yaml
---
r: 284383
b: refs/heads/swift-5.1-branch
c: 5c42961
h: refs/heads/master
i:
  284381: 90a7b0a
  284379: fd4d9c6
  284375: 67ca6eb
  284367: 8b9df93
  284351: 0773ae6

Author: jckarter

[refs]

@@ -1242,7 +1242,7 @@ refs/heads/marcrasi-astverifier-disable: 3fac766a23a77ebd0640296bfd7fc116ea60a4e
 refs/heads/revert-22227-a-tall-white-fountain-played: adfce60b2eaa54903ea189bed8a783bca609fa53
 refs/heads/revert-22300-revert-22227-a-tall-white-fountain-played: 5f92040224df7dd4e618fdfb367349df64d8acad
 refs/heads/swift-5.1-old-llvm-branch: 9cef8175146f25b72806154b8a0f4a3f52e3e400
-refs/heads/swift-5.1-branch: 4a28dfc13bba4a5910820d4070f4d6e8b7605444
+refs/heads/swift-5.1-branch: 5c42961c9c366503b7108eb066f54b43677c4b98
 refs/tags/swift-4.2.2-RELEASE: e429d1f1aaf59e69d38207a96e56265c7f6fccec
 refs/tags/swift-5.0-DEVELOPMENT-SNAPSHOT-2019-02-02-a: 3e5a03d32ff3b1e9af90d6c1198c14f938379a6e
 refs/tags/swift-5.0-DEVELOPMENT-SNAPSHOT-2019-02-03-a: 4591c933063ddcb0d6cd6d0cdd01086b2f9b244d

branches/swift-5.1-branch/include/swift/AST/DiagnosticsSema.def

@@ -1519,6 +1519,9 @@ WARNING(function_type_usable_from_inline_warn,none,
 ERROR(opaque_type_invalid_constraint,none,
       "an 'opaque' type must specify only 'Any', 'AnyObject', protocols, "
       "and/or a base class", ())
+ERROR(inferred_opaque_type,none,
+      "property definition has inferred type %0, involving the '__opaque' "
+      "return type of another declaration", (Type))
 
 // Extensions
 ERROR(non_nominal_extension,none,

branches/swift-5.1-branch/lib/Sema/TypeCheckDecl.cpp

@@ -987,6 +987,15 @@ static void validatePatternBindingEntry(TypeChecker &tc,
   if (!pattern->hasType() || pattern->getType()->hasUnboundGenericType()) {
     if (tc.typeCheckPatternBinding(binding, entryNumber))
       return;
+    
+    // A pattern binding at top level is not allowed to pick up another decl's
+    // opaque result type as its type by type inference.
+    if (!binding->getDeclContext()->isLocalContext()
+        && binding->getInit(entryNumber)->getType()->hasOpaqueArchetype()) {
+      // TODO: Check whether the type is the pattern binding's own opaque type.
+      tc.diagnose(binding, diag::inferred_opaque_type,
+                  binding->getInit(entryNumber)->getType());
+    }
   }
 
   // If the pattern binding appears in a type or library file context, then

branches/swift-5.1-branch/test/type/opaque.swift

@@ -56,6 +56,14 @@ func zlop() -> __opaque C & AnyObject & P {
   return D()
 }
 
+// Don't allow opaque types to propagate by inference into other global decls'
+// types
+struct Test {
+  let inferredOpaque = bar() // expected-error{{inferred type}}
+  let inferredOpaqueStructural = Optional(bar()) // expected-error{{inferred type}}
+  let inferredOpaqueStructural2 = (bar(), bas()) // expected-error{{inferred type}}
+}
+
 //let zingle = {() -> __opaque P in 1 } // FIXME ex/pected-error{{'opaque' types are only implemented}}
 
 // Invalid positions