[sil-generic-specializer] Fix a bug related to cloning of self-referring generic closures

Fixes rdar://31776399

include/swift/SIL/TypeSubstCloner.h

@@ -145,25 +145,39 @@ protected:
     SILValue CalleeVal = Inst->getCallee();
     SILBuilderWithPostProcess<TypeSubstCloner, 4> Builder(this, Inst);
     Builder.setCurrentDebugScope(super::getOpScope(Inst->getDebugScope()));
+    SmallVector<Substitution, 16> TempSubstList;
     if (!Inlining) {
       FunctionRefInst *FRI = dyn_cast<FunctionRefInst>(CalleeVal);
       if (FRI && FRI->getReferencedFunction() == Inst->getFunction()) {
+        auto LoweredFnTy = Builder.getFunction().getLoweredFunctionType();
+        auto GenSig = LoweredFnTy->getGenericSignature();
+        if (GenSig) {
+          GenSig->getSubstitutions(
+              Inst->getFunction()
+                  ->getLoweredFunctionType()
+                  ->getGenericSignature()
+                  ->getSubstitutionMap(Inst->getSubstitutions()),
+              TempSubstList);
+        }
+        for (auto &Sub : TempSubstList) {
+          Sub = asImpl().getOpSubstitution(Sub);
+        }
+        SubstitutionList Subs = TempSubstList;
         FRI = Builder.createFunctionRef(getOpLocation(Inst->getLoc()),
                                         &Builder.getFunction());
         Builder.createPartialApply(getOpLocation(Inst->getLoc()), FRI,
                                    getOpType(Inst->getSubstCalleeSILType()),
-                                   SubstitutionList(),
+                                   Subs,
                                    Args,
                                    getOpType(Inst->getType()));
         return;
       }
     }
 
-    SmallVector<Substitution, 16> TempSubstList;
     for (auto &Sub : Inst->getSubstitutions()) {
       TempSubstList.push_back(asImpl().getOpSubstitution(Sub));
     }
-    
+
     Builder.createPartialApply(
       getOpLocation(Inst->getLoc()), getOpValue(CalleeVal),
         getOpType(Inst->getSubstCalleeSILType()), TempSubstList, Args,

test/SILOptimizer/specialize.sil

@@ -582,3 +582,35 @@ bb0:
   %12 = tuple ()
   return %12 : $()
 } // end sil function 'testGenericClosureSpecialization'
+
+// Test a specialization of a self-recursive generic closure.
+
+// CHECK-LABEL: sil shared @_T027selfReferringGenericClosurexBi64_Bi64_Bi64_Rs_r0_lItnny_Tp5 : $@convention(thin) <τ_0_0, τ_0_1 where τ_0_1 == Builtin.Int64> (@in_guaranteed τ_0_0, @in_guaranteed Builtin.Int64, Builtin.Int64) -> ()
+// CHECK: [[SPECIALIZED_FN:%[0-9]+]] = function_ref @_T027selfReferringGenericClosurexBi64_Bi64_Bi64_Rs_r0_lItnny_Tp5
+// CHECK: partial_apply [[SPECIALIZED_FN]]{{.*}}({{.*}}) : $@convention(thin) <τ_0_0, τ_0_1 where τ_0_1 == Builtin.Int64> (@in_guaranteed τ_0_0, @in_guaranteed Builtin.Int64, Builtin.Int64) -> ()
+
+// CHECK-LABEL: sil @selfReferringGenericClosure : $@convention(thin) <R, S> (@in_guaranteed R, @in_guaranteed S, Builtin.Int64) -> ()
+// Refer to the specialized version of the function
+// CHECK: [[SPECIALIZED_FN:%[0-9]+]] = function_ref @_T027selfReferringGenericClosurexBi64_Bi64_Bi64_Rs_r0_lItnny_Tp5
+// CHECK: partial_apply [[SPECIALIZED_FN]]<R>({{.*}}) : $@convention(thin) <τ_0_0, τ_0_1 where τ_0_1 == Builtin.Int64> (@in_guaranteed τ_0_0, @in_guaranteed Builtin.Int64, Builtin.Int64) -> ()
+sil @selfReferringGenericClosure : $@convention(thin) <R, S> (@in_guaranteed R, @in_guaranteed S, Builtin.Int64) -> () {
+bb0(%0 : $*R, %1 : $*S, %2 : $Builtin.Int64):
+  %4 = integer_literal $Builtin.Int64, 100
+  %5 = builtin "cmp_eq_Int64"(%2 : $Builtin.Int64, %4 : $Builtin.Int64) : $Builtin.Int1
+  cond_br %5, bb2, bb1
+
+bb1:
+  %val_storage = alloc_stack $Builtin.Int64
+  %val = integer_literal $Builtin.Int64, 4
+  store %val to %val_storage : $*Builtin.Int64
+  %fn = function_ref @selfReferringGenericClosure : $@convention(thin) <U, V> (@in_guaranteed U, @in_guaranteed V, Builtin.Int64) -> () 
+  %7 = partial_apply %fn<R, Builtin.Int64>(%0, %val_storage, %4) : $@convention(thin) <U, V> (@in_guaranteed U, @in_guaranteed V, Builtin.Int64) -> ()
+  dealloc_stack %val_storage : $*Builtin.Int64
+  br bb3
+bb2:
+  br bb3
+
+bb3:
+  %8 = tuple ()
+  return %8 : $()
+}