Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -8654,7 +8654,7 @@
                                         Expr *CastExpr,
                                         SourceLocation RParenLoc);
 
-  enum ARCConversionResult { ACR_okay, ACR_unbridged };
+  enum ARCConversionResult { ACR_okay, ACR_unbridged, ACR_error };
 
   /// \brief Checks for invalid conversions and casts between
   /// retainable pointers and other pointer kinds.
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -7566,15 +7566,23 @@
   if (result != Incompatible && RHS.get()->getType() != LHSType) {
     QualType Ty = LHSType.getNonLValueExprType(Context);
     Expr *E = RHS.get();
-    if (getLangOpts().ObjCAutoRefCount)
-      CheckObjCARCConversion(SourceRange(), Ty, E, CCK_ImplicitConversion,
-                             Diagnose, DiagnoseCFAudited);
+    if (getLangOpts().ObjCAutoRefCount &&
+        CheckObjCARCConversion(SourceRange(), Ty, E, CCK_ImplicitConversion,
+                               Diagnose, DiagnoseCFAudited) != ACR_okay) {
+      if (!Diagnose)
+        result = Incompatible;
+    }
     if (getLangOpts().ObjC1 &&
         (CheckObjCBridgeRelatedConversions(E->getLocStart(), LHSType,
                                            E->getType(), E, Diagnose) ||
          ConversionToObjCStringLiteralCheck(LHSType, E, Diagnose))) {
-      RHS = E;
-      return Compatible;
+      if (Diagnose) {
+        // If an error was diagnosed here, replace the expression with a
+        // corrected version and continue so we can find further errors.
+        RHS = E;
+        return Compatible;
+      }
+      result = Incompatible;
     }
     
     if (ConvertRHS)
@@ -12035,10 +12043,11 @@
   StringLiteral *SL = dyn_cast<StringLiteral>(SrcExpr);
   if (!SL || !SL->isAscii())
     return false;
-  if (Diagnose)
+  if (Diagnose) {
     Diag(SL->getLocStart(), diag::err_missing_atsign_prefix)
       << FixItHint::CreateInsertion(SL->getLocStart(), "@");
-  Exp = BuildObjCStringLiteral(SL->getLocStart(), SL).get();
+    Exp = BuildObjCStringLiteral(SL->getLocStart(), SL).get();
+  }
   return true;
 }
 
Index: lib/Sema/SemaExprObjC.cpp
===================================================================
--- lib/Sema/SemaExprObjC.cpp
+++ lib/Sema/SemaExprObjC.cpp
@@ -3478,6 +3478,8 @@
     return;
 
   QualType castExprType = castExpr->getType();
+  // Defer emitting a diagnostic for bridge-related casts; that will be
+  // handled by CheckObjCBridgeRelatedConversions.
   TypedefNameDecl *TDNDecl = nullptr;
   if ((castACTC == ACTC_coreFoundation &&  exprACTC == ACTC_retainable &&
        ObjCBridgeRelatedAttrFromType(castType, TDNDecl)) ||
@@ -3922,16 +3924,16 @@
           << FixItHint::CreateInsertion(SrcExprEndLoc, "]");
         Diag(RelatedClass->getLocStart(), diag::note_declared_at);
         Diag(TDNDecl->getLocStart(), diag::note_declared_at);
-      }
       
-      QualType receiverType = Context.getObjCInterfaceType(RelatedClass);
-      // Argument.
-      Expr *args[] = { SrcExpr };
-      ExprResult msg = BuildClassMessageImplicit(receiverType, false,
+        QualType receiverType = Context.getObjCInterfaceType(RelatedClass);
+        // Argument.
+        Expr *args[] = { SrcExpr };
+        ExprResult msg = BuildClassMessageImplicit(receiverType, false,
                                       ClassMethod->getLocation(),
                                       ClassMethod->getSelector(), ClassMethod,
                                       MultiExprArg(args, 1));
-      SrcExpr = msg.get();
+        SrcExpr = msg.get();
+      }
       return true;
     }
   }
@@ -3965,14 +3967,14 @@
         }
         Diag(RelatedClass->getLocStart(), diag::note_declared_at);
         Diag(TDNDecl->getLocStart(), diag::note_declared_at);
-      }
       
-      ExprResult msg =
-        BuildInstanceMessageImplicit(SrcExpr, SrcType,
-                                     InstanceMethod->getLocation(),
-                                     InstanceMethod->getSelector(),
-                                     InstanceMethod, None);
-      SrcExpr = msg.get();
+        ExprResult msg =
+          BuildInstanceMessageImplicit(SrcExpr, SrcType,
+                                       InstanceMethod->getLocation(),
+                                       InstanceMethod->getSelector(),
+                                       InstanceMethod, None);
+        SrcExpr = msg.get();
+      }
       return true;
     }
   }
@@ -3996,9 +3998,9 @@
   ARCConversionTypeClass exprACTC = classifyTypeForARCConversion(castExprType);
   ARCConversionTypeClass castACTC = classifyTypeForARCConversion(effCastType);
   if (exprACTC == castACTC) {
-    // check for viablity and report error if casting an rvalue to a
+    // Check for viability and report error if casting an rvalue to a
     // life-time qualifier.
-    if (Diagnose && castACTC == ACTC_retainable &&
+    if (castACTC == ACTC_retainable &&
         (CCK == CCK_CStyleCast || CCK == CCK_OtherCast) &&
         castType != castExprType) {
       const Type *DT = castType.getTypePtr();
@@ -4014,10 +4016,12 @@
         QDT = AT->desugar();
       if (QDT != castType &&
           QDT.getObjCLifetime() !=  Qualifiers::OCL_None) {
-        SourceLocation loc =
-          (castRange.isValid() ? castRange.getBegin() 
-                              : castExpr->getExprLoc());
-        Diag(loc, diag::err_arc_nolifetime_behavior);
+        if (Diagnose) {
+          SourceLocation loc = (castRange.isValid() ? castRange.getBegin() 
+                                                    : castExpr->getExprLoc());
+          Diag(loc, diag::err_arc_nolifetime_behavior);
+        }
+        return ACR_error;
       }
     }
     return ACR_okay;
@@ -4065,24 +4069,26 @@
       CCK != CCK_ImplicitConversion)
     return ACR_unbridged;
 
-  // Do not issue bridge cast" diagnostic when implicit casting a cstring
-  // to 'NSString *'. Let caller issue a normal mismatched diagnostic with
-  // suitable fix-it.
+  // Issue a diagnostic about a missing @-sign when implicit casting a cstring
+  // to 'NSString *', instead of falling through to report a "bridge cast"
+  // diagnostic.
   if (castACTC == ACTC_retainable && exprACTC == ACTC_none &&
       ConversionToObjCStringLiteralCheck(castType, castExpr, Diagnose))
-    return ACR_okay;
+    return ACR_error;
   
   // Do not issue "bridge cast" diagnostic when implicit casting
   // a retainable object to a CF type parameter belonging to an audited
   // CF API function. Let caller issue a normal type mismatched diagnostic
   // instead.
-  if (Diagnose &&
-      (!DiagnoseCFAudited || exprACTC != ACTC_retainable ||
-        castACTC != ACTC_coreFoundation))
-    if (!(exprACTC == ACTC_voidPtr && castACTC == ACTC_retainable &&
-          (Opc == BO_NE || Opc == BO_EQ)))
+  if ((!DiagnoseCFAudited || exprACTC != ACTC_retainable ||
+       castACTC != ACTC_coreFoundation) &&
+      !(exprACTC == ACTC_voidPtr && castACTC == ACTC_retainable &&
+        (Opc == BO_NE || Opc == BO_EQ))) {
+    if (Diagnose)
       diagnoseObjCARCConversion(*this, castRange, castType, castACTC, castExpr,
                                 castExpr, exprACTC, CCK);
+    return ACR_error;
+  }
   return ACR_okay;
 }
 
Index: test/SemaObjC/ovl-check.m
===================================================================
--- test/SemaObjC/ovl-check.m
+++ test/SemaObjC/ovl-check.m
@@ -4,20 +4,24 @@
 // in overload resolution in ObjC.
 
 struct Type1 { int a; };
+typedef const __attribute__((objc_bridge(id))) void * Type2;
 @interface Iface1 @end
 
 @interface NeverCalled
 - (void) test:(struct Type1 *)arg;
+- (void) test2:(Type2 )arg;
 @end
 
 @interface TakesIface1
 - (void) test:(Iface1 *)arg;
+- (void) test2:(Iface1 *)arg;
 @end
 
 // PR26085, rdar://problem/24111333
 void testTakesIface1(id x, Iface1 *arg) {
   // This should resolve silently to `TakesIface1`.
   [x test:arg];
+  [x test2:arg];
 }
 
 @class NSString;