Revert "[region-isolation] Make "unknown pattern error" always an error."

This reverts commit b63781f.

We found some cases where due to malformed IR that we allow through due to
either us compiling for strict-concurrency=complete+swift-5 or swift-6 +
preconcurrency, that we can actually have actor isolation mismatch. I am going
to in a subsequent commit add a better phrasing here. But for now, just undo the
conversion from error -> warning.

rdar://131757602

Author: gottesmm

lib/SILOptimizer/Mandatory/TransferNonSendable.cpp

@@ -158,23 +158,6 @@ static Expr *inferArgumentExprFromApplyExpr(ApplyExpr *sourceApply,
 //                             MARK: Diagnostics
 //===----------------------------------------------------------------------===//
 
-/// Emit the "unknown pattern error" at the SILLocation of \p inst.
-static void diagnoseUnknownPatternError(SILInstruction *inst) {
-  if (shouldAbortOnUnknownPatternMatchError()) {
-    llvm::report_fatal_error(
-        "RegionIsolation: Aborting on unknown pattern match error");
-  }
-
-  auto &ctx = inst->getFunction()->getASTContext();
-  auto loc = inst->getLoc().getSourceLoc();
-
-  ctx.Diags.diagnose(loc, diag::regionbasedisolation_unknown_pattern);
-}
-
-static void diagnoseUnknownPatternError(Operand *op) {
-  diagnoseUnknownPatternError(op->getUser());
-}
-
 template <typename... T, typename... U>
 static InFlightDiagnostic diagnoseError(ASTContext &context, SourceLoc loc,
                                         Diag<T...> diag, U &&...args) {
@@ -749,7 +732,14 @@ class UseAfterTransferDiagnosticEmitter {
   }
 
   void emitUnknownPatternError() {
-    diagnoseUnknownPatternError(transferOp->getUser());
+    if (shouldAbortOnUnknownPatternMatchError()) {
+      llvm::report_fatal_error(
+          "RegionIsolation: Aborting on unknown pattern match error");
+    }
+
+    diagnoseError(transferOp->getUser(),
+                  diag::regionbasedisolation_unknown_pattern)
+        .limitBehaviorIf(getBehaviorLimit());
   }
 
 private:
@@ -1170,7 +1160,12 @@ void TransferNonSendableImpl::emitUseAfterTransferDiagnostics() {
     // tells the user to file a bug. This importantly ensures that we can
     // guarantee that we always find the require if we successfully compile.
     if (!didEmitRequireNote) {
-      diagnoseUnknownPatternError(transferOp);
+      if (shouldAbortOnUnknownPatternMatchError()) {
+        llvm::report_fatal_error(
+            "RegionIsolation: Aborting on unknown pattern match error");
+      }
+
+      diagnoseError(transferOp, diag::regionbasedisolation_unknown_pattern);
       continue;
     }
 
@@ -1232,7 +1227,14 @@ class TransferNonTransferrableDiagnosticEmitter {
   }
 
   void emitUnknownPatternError() {
-    diagnoseUnknownPatternError(getOperand()->getUser());
+    if (shouldAbortOnUnknownPatternMatchError()) {
+      llvm::report_fatal_error(
+          "RegionIsolation: Aborting on unknown pattern match error");
+    }
+
+    diagnoseError(getOperand()->getUser(),
+                  diag::regionbasedisolation_unknown_pattern)
+        .limitBehaviorIf(getBehaviorLimit());
   }
 
   void emitUnknownUse(SILLocation loc) {
@@ -1725,7 +1727,14 @@ class InOutSendingNotDisconnectedDiagnosticEmitter {
   }
 
   void emitUnknownPatternError() {
-    diagnoseUnknownPatternError(info.functionExitingInst);
+    if (shouldAbortOnUnknownPatternMatchError()) {
+      llvm::report_fatal_error(
+          "RegionIsolation: Aborting on unknown pattern match error");
+    }
+
+    diagnoseError(info.functionExitingInst,
+                  diag::regionbasedisolation_unknown_pattern)
+        .limitBehaviorIf(getBehaviorLimit());
   }
 
   void emit();
@@ -1985,7 +1994,13 @@ struct DiagnosticEvaluator final
   }
 
   void handleUnknownCodePattern(const PartitionOp &op) const {
-    diagnoseUnknownPatternError(op.getSourceInst());
+    if (shouldAbortOnUnknownPatternMatchError()) {
+      llvm::report_fatal_error(
+          "RegionIsolation: Aborting on unknown pattern match error");
+    }
+
+    diagnoseError(op.getSourceInst(),
+                  diag::regionbasedisolation_unknown_pattern);
   }
 
   bool isActorDerived(Element element) const {