SILGen: Don't use diagnoseUnexpectedEnumCase intrinsic for noncopyable enums.

It should be impossible to reach an unexpected case statically while using
noncopyable enums, and the intrinsic has not been updated to remove its
`Copyable` requirement. Emit a plain trap in cases where this code emission
path might still occur, such as when a redundant but incomplete set of case
patterns follow a wildcard pattern. Fixes rdar://130037881.

lib/SILGen/SILGenPattern.cpp

@@ -3109,6 +3109,13 @@ static void emitDiagnoseOfUnexpectedEnumCaseValue(SILGenFunction &SGF,
 static void emitDiagnoseOfUnexpectedEnumCase(SILGenFunction &SGF,
                                              SILLocation loc,
                                              UnexpectedEnumCaseInfo ueci) {
+  if (ueci.subjectTy->isNoncopyable()) {
+    // TODO: The DiagnoseUnexpectedEnumCase intrinsic currently requires a
+    // Copyable parameter. For noncopyable enums it should be impossible to
+    // reach an unexpected case statically, so just emit a trap for now.
+    SGF.B.createUnconditionalFail(loc, "unexpected enum case");
+    return;
+  }
   ASTContext &ctx = SGF.getASTContext();
   auto diagnoseFailure = ctx.getDiagnoseUnexpectedEnumCase();
   if (!diagnoseFailure) {

test/SILGen/noncopyable_enum_unexpected_case.swift

@@ -0,0 +1,17 @@
+// RUN: %target-swift-emit-silgen -verify %s
+
+struct NC: ~Copyable {}
+
+enum NoncopyableEnum: ~Copyable {
+  case copyable(Int)
+  case noncopyable(NC)
+}
+
+func test(foo: consuming NoncopyableEnum) {
+  switch foo {
+  case let x: // expected-warning{{'x' was never used}}
+    break
+  case .copyable(let x): // expected-warning{{already handled by previous patterns}} expected-warning{{'x' was never used}}
+    break
+  }
+}