diff --git a/include/swift/Basic/LangOptions.h b/include/swift/Basic/LangOptions.h
index fb6ed509888..a0fadc0bfac 100644
--- a/include/swift/Basic/LangOptions.h
+++ b/include/swift/Basic/LangOptions.h
@@ -991,6 +991,10 @@ namespace swift {
     /// debugging
     unsigned ShuffleDisjunctionChoicesSeed = 0;
 
+    /// If true, we will crash if the constraint solver found a valid solution
+    /// in diagnostic mode.
+    bool CrashOnValidSalvage = false;
+
     /// Triggers llvm fatal error if the typechecker tries to typecheck a decl
     /// or an identifier reference with any of the provided prefix names. This
     /// is for testing purposes.
diff --git a/include/swift/Option/FrontendOptions.td b/include/swift/Option/FrontendOptions.td
index aa164c56156..9736a698928 100644
--- a/include/swift/Option/FrontendOptions.td
+++ b/include/swift/Option/FrontendOptions.td
@@ -438,8 +438,11 @@ def solver_shuffle_disjunctions_EQ : Joined<["-"], "solver-shuffle-disjunctions=
 def solver_shuffle_choices_EQ : Joined<["-"], "solver-shuffle-choices=">,
   HelpText<"Random seed for shuffling disjunction choices. For debugging solver performance">;
 
-def disable_named_lazy_member_loading : Flag<["-"], "disable-named-lazy-member-loading">,
-  HelpText<"Disable per-name lazy member loading (obsolete)">;
+def solver_enable_crash_on_valid_salvage : Flag<["-"], "solver-enable-crash-on-valid-salvage">,
+  HelpText<"Reject valid solutions in diagnostic mode">;
+
+def solver_disable_crash_on_valid_salvage : Flag<["-"], "solver-disable-crash-on-valid-salvage">,
+  HelpText<"Accept valid solutions in diagnostic mode">;
 
 def disable_named_lazy_import_as_member_loading :
   Flag<["-"], "disable-named-lazy-import-as-member-loading">,
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 080f0f49d3d..7bc515279e8 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -2127,21 +2127,30 @@ static bool ParseTypeCheckerArgs(TypeCheckerOptions &Opts, ArgList &Args,
   if (Args.getLastArg(OPT_solver_disable_splitter))
     Opts.SolverDisableSplitter = true;
 
-  if (Args.hasArg(OPT_solver_enable_prepared_overloads) ||
-      Args.hasArg(OPT_solver_disable_prepared_overloads))
-    Opts.SolverEnablePreparedOverloads = Args.hasArg(OPT_solver_enable_prepared_overloads);
+  Opts.CrashOnValidSalvage =
+      Args.hasFlag(OPT_solver_enable_crash_on_valid_salvage,
+                   OPT_solver_disable_crash_on_valid_salvage,
+                   Opts.CrashOnValidSalvage);
 
-  if (Args.hasArg(OPT_solver_enable_prune_disjunctions) ||
-      Args.hasArg(OPT_solver_disable_prune_disjunctions))
-    Opts.SolverPruneDisjunctions = Args.hasArg(OPT_solver_enable_prune_disjunctions);
+  Opts.SolverEnablePreparedOverloads =
+      Args.hasFlag(OPT_solver_enable_prepared_overloads,
+                   OPT_solver_disable_prepared_overloads,
+                   Opts.SolverEnablePreparedOverloads);
 
-  if (Args.hasArg(OPT_solver_enable_optimize_operator_defaults) ||
-      Args.hasArg(OPT_solver_disable_optimize_operator_defaults))
-    Opts.SolverOptimizeOperatorDefaults = Args.hasArg(OPT_solver_enable_optimize_operator_defaults);
+  Opts.SolverPruneDisjunctions =
+      Args.hasFlag(OPT_solver_enable_prune_disjunctions,
+                   OPT_solver_disable_prune_disjunctions,
+                   Opts.SolverPruneDisjunctions);
 
-  if (Args.hasArg(OPT_solver_enable_performance_hacks) ||
-      Args.hasArg(OPT_solver_disable_performance_hacks))
-    Opts.SolverEnablePerformanceHacks = Args.hasArg(OPT_solver_enable_performance_hacks);
+  Opts.SolverOptimizeOperatorDefaults =
+      Args.hasFlag(OPT_solver_enable_optimize_operator_defaults,
+                   OPT_solver_disable_optimize_operator_defaults,
+                   Opts.SolverOptimizeOperatorDefaults);
+
+  Opts.SolverEnablePerformanceHacks =
+      Args.hasFlag(OPT_solver_enable_performance_hacks,
+                   OPT_solver_disable_performance_hacks,
+                   Opts.SolverEnablePerformanceHacks);
 
   if (FrontendOpts.RequestedAction == FrontendOptions::ActionType::Immediate)
     Opts.DeferToRuntime = true;
diff --git a/lib/Sema/ConstraintSystem.cpp b/lib/Sema/ConstraintSystem.cpp
index c1307acb696..424cc6e5bdd 100644
--- a/lib/Sema/ConstraintSystem.cpp
+++ b/lib/Sema/ConstraintSystem.cpp
@@ -2028,6 +2028,22 @@ SolutionResult ConstraintSystem::salvage() {
       if (*best != 0)
         viable[0] = std::move(viable[*best]);
       viable.erase(viable.begin() + 1, viable.end());
+
+      if (getASTContext().TypeCheckerOpts.CrashOnValidSalvage) {
+        auto &solution = viable[0];
+        if (solution.Fixes.empty() &&
+            diagnosticTransaction == nullptr &&
+            !getASTContext().LangOpts.DisableAvailabilityChecking &&
+            solution.getFixedScore().Data[SK_Unavailable] == 0 &&
+            solution.getFixedScore().Data[SK_Hole] == 0 &&
+            solution.getFixedScore().Data[SK_Fix] == 0) {
+          ABORT([&](auto &out) {
+            out << "Found valid solution in salvage()\n\n";
+            solution.dump(out, 0);
+          });
+        }
+      }
+
       return SolutionResult::forSolved(std::move(viable[0]));
     }
 
diff --git a/test/Constraints/solution_with_holes.swift b/test/Constraints/solution_with_holes.swift
new file mode 100644
index 00000000000..4c9bd009c37
--- /dev/null
+++ b/test/Constraints/solution_with_holes.swift
@@ -0,0 +1,14 @@
+// RUN: %target-typecheck-verify-swift
+
+protocol P {
+  associatedtype X // expected-note {{protocol requires nested type 'X'}}
+}
+
+struct S: P {} // expected-error {{type 'S' does not conform to protocol 'P'}}
+// expected-note@-1 {{add stubs for conformance}}
+
+func foo<T: P>(_ x: T) -> T.X {}
+
+func bar(_ x: S) {
+  foo(x) // result of foo() is a hole
+}