[move-only] Eliminate dead field.

Originally this was a method to determine if we had emitted a diagnostic when
running our gather visitor. It was pretty footgunny since one could easily
forget to set it. Instead of doing that, we now maintain a counter in the
diagnostic emitter that counts how many diagnostics we have emitted and use that
to determine if during the walk if we emitted any additional diagnostics.

(cherry picked from commit d252902)

Author: gottesmm

lib/SILOptimizer/Mandatory/MoveOnlyAddressCheckerUtils.cpp

@@ -1441,7 +1441,6 @@ struct GatherUsesVisitor final : public TransitiveAddressWalker {
   MoveOnlyAddressCheckerPImpl &moveChecker;
   UseState &useState;
   MarkMustCheckInst *markedValue;
-  bool emittedEarlyDiagnostic = false;
   DiagnosticEmitter &diagnosticEmitter;
 
   // Pruned liveness used to validate that load [take]/load [copy] can be
@@ -1616,14 +1615,13 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
       if (isa<ProjectBoxInst>(stripAccessMarkers(markedValue->getOperand()))) {
         LLVM_DEBUG(llvm::dbgs()
                    << "Found mark must check [nocopy] use of escaping box: " << *user);
-        diagnosticEmitter.emitAddressEscapingClosureCaptureLoadedAndConsumed(markedValue);
-        emittedEarlyDiagnostic = true;
+        diagnosticEmitter.emitAddressEscapingClosureCaptureLoadedAndConsumed(
+            markedValue);
         return true;
       }
       LLVM_DEBUG(llvm::dbgs()
                  << "Found mark must check [nocopy] error: " << *user);
       diagnosticEmitter.emitAddressDiagnosticNoCopy(markedValue, copyAddr);
-      emittedEarlyDiagnostic = true;
       return true;
     }
 
@@ -1679,15 +1677,13 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
                  .didEmitCheckerDoesntUnderstandDiagnostic());
       LLVM_DEBUG(llvm::dbgs()
                  << "Failed to perform borrow to destructure transform!\n");
-      emittedEarlyDiagnostic = true;
       return false;
     }
 
     // If we emitted an error diagnostic, do not transform further and instead
     // mark that we emitted an early diagnostic and return true.
     if (numDiagnostics != moveChecker.diagnosticEmitter.getDiagnosticCount()) {
       LLVM_DEBUG(llvm::dbgs() << "Emitting borrow to destructure error!\n");
-      emittedEarlyDiagnostic = true;
       return true;
     }
 
@@ -1708,7 +1704,6 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
     if (numDiagnostics != moveChecker.diagnosticEmitter.getDiagnosticCount()) {
       LLVM_DEBUG(llvm::dbgs()
                  << "Emitting destructure through deinit error!\n");
-      emittedEarlyDiagnostic = true;
       return true;
     }
 
@@ -1738,7 +1733,6 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
           moveChecker.diagnosticEmitter
               .emitAddressEscapingClosureCaptureLoadedAndConsumed(markedValue);
         }
-        emittedEarlyDiagnostic = true;
         return true;
       }
 
@@ -1752,7 +1746,6 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
 
       if (checkForExclusivityHazards(li)) {
         LLVM_DEBUG(llvm::dbgs() << "Found exclusivity violation?!\n");
-        emittedEarlyDiagnostic = true;
         return true;
       }
 
@@ -1785,7 +1778,6 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
       // succeeded.
       // Otherwise, emit the diagnostic.
       moveChecker.diagnosticEmitter.emitObjectOwnedDiagnostic(markedValue);
-      emittedEarlyDiagnostic = true;
       LLVM_DEBUG(llvm::dbgs() << "Emitted early object level diagnostic.\n");
       return true;
     }
@@ -1794,7 +1786,6 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
       LLVM_DEBUG(llvm::dbgs() << "Found potential borrow inst: " << *user);
       if (checkForExclusivityHazards(li)) {
         LLVM_DEBUG(llvm::dbgs() << "Found exclusivity violation?!\n");
-        emittedEarlyDiagnostic = true;
         return true;
       }
 
@@ -1843,7 +1834,6 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
         moveChecker.diagnosticEmitter
             .emitAddressEscapingClosureCaptureLoadedAndConsumed(markedValue);
       }
-      emittedEarlyDiagnostic = true;
       return true;
     }