[FixedArray] Fix TypeLowering verification.

A new aggregate type has been added and must be walked into.

rdar://139448358

Author: nate-chandler

lib/SIL/IR/TypeLowering.cpp

@@ -3000,6 +3000,7 @@ bool TypeConverter::visitAggregateLeaves(
     return isa<SILPackType>(ty) ||
            isa<TupleType>(ty) ||
            isa<PackExpansionType>(ty) ||
+           isa<BuiltinFixedArrayType>(ty) ||
            ty.getEnumOrBoundGenericEnum() ||
            ty.getStructOrBoundGenericStruct();
   };
@@ -3036,6 +3037,13 @@ bool TypeConverter::visitAggregateLeaves(
         insertIntoWorklist(expansion.getPatternType(),
                            origTy.getPackExpansionPatternType(),
                            field, index);
+      } else if (auto array = dyn_cast<BuiltinFixedArrayType>(ty)) {
+        auto origBFA = origTy.getAs<BuiltinFixedArrayType>();
+        insertIntoWorklist(
+            array->getElementType(),
+            AbstractionPattern(origTy.getGenericSignatureOrNull(),
+                               origBFA->getElementType()),
+            field, index);
       } else if (auto *decl = ty.getStructOrBoundGenericStruct()) {
         for (auto *structField : decl->getStoredProperties()) {
           auto subMap = ty->getContextSubstitutionMap();

test/SILGen/bitwise_copyable.swift

@@ -1,11 +1,18 @@
-// RUN: %target-swift-frontend                                  \
-// RUN:     %s                                                  \
-// RUN:     -emit-silgen                                        \
-// RUN:     -target %target-swift-5.1-abi-triple                      \
-// RUN:     -enable-experimental-feature Sensitive              \
+// RUN: %target-swift-frontend                         \
+// RUN:     %s                                         \
+// RUN:     -emit-silgen                               \
+// RUN:     -disable-experimental-parser-round-trip    \
+// RUN:     -target %target-swift-5.1-abi-triple       \
+// RUN:     -enable-experimental-feature Sensitive     \
+// RUN:     -enable-experimental-feature ValueGenerics \
 // RUN:     -enable-builtin-module
 
+// FIXME: Remove -disable-experimental-parser-round-trip when it's not required for using ValueGenerics.
+
 // REQUIRES: swift_feature_Sensitive
+// REQUIRES: swift_feature_ValueGenerics
+
+// REQUIRES: asserts
 
 // Force verification of TypeLowering's isTrivial.
 
@@ -68,3 +75,10 @@ struct S_Explicit_Sensitive {
 
 func takeS_Explicit_Sensitive(_ s: S_Explicit_Sensitive) {
 }
+
+import Builtin
+
+func foo() {
+  let bricks: Builtin.FixedArray<1, Conditional<Int>>
+  let bricks2: Builtin.FixedArray<1, Conditional<String>>
+}