SILGen: Fix for 'try?' leaking the error value

The error is passed in to the catch block as a +1 value but
we were just dropping it on the floor.

Fixes https://bugs.swift.org/browse/SR-972

Author: slavapestov

lib/SILGen/SILGenExpr.cpp

@@ -997,7 +997,11 @@ RValue RValueEmitter::visitOptionalTryExpr(OptionalTryExpr *E, SGFContext C) {
   // If control branched to the failure block, inject .None into the
   // result type.
   SGF.B.emitBlock(catchBB);
-  (void)catchBB->createBBArg(SILType::getExceptionType(SGF.getASTContext()));
+  FullExpr catchCleanups(SGF.Cleanups, E);
+  auto *errorArg = catchBB->createBBArg(
+      SILType::getExceptionType(SGF.getASTContext()));
+  (void) SGF.emitManagedRValueWithCleanup(errorArg);
+  catchCleanups.pop();
 
   if (isByAddress) {
     SGF.emitInjectOptionalNothingInto(E, optInit->getAddress(), optTL);

test/Interpreter/errors.swift

@@ -0,0 +1,54 @@
+// RUN: %target-run-simple-swift
+// REQUIRES: executable_test
+
+//
+// Tests for error handling.
+//
+
+import StdlibUnittest
+
+// Also import modules which are used by StdlibUnittest internally. This
+// workaround is needed to link all required libraries in case we compile
+// StdlibUnittest with -sil-serialize-all.
+import SwiftPrivate
+#if _runtime(_ObjC)
+import ObjectiveC
+#endif
+
+enum Excuse : ErrorProtocol { case CatAteHomework(LifetimeTracked) }
+
+var ErrorHandlingTests = TestSuite("ErrorHandling")
+
+func furball(b: Bool) throws -> LifetimeTracked {
+  if b {
+    throw Excuse.CatAteHomework(LifetimeTracked(0))
+  } else {
+    return LifetimeTracked(1)
+  }
+}
+
+ErrorHandlingTests.test("tryCatch") {
+  do {
+    try expectEqual(furball(false), LifetimeTracked(1))
+  } catch {
+    expectUnreachable() 
+  }
+
+  do {
+    try furball(true)
+    expectUnreachable() 
+  } catch let e {
+    if case Excuse.CatAteHomework(let c) = e {
+      expectEqual(c, LifetimeTracked(0))
+    } else {
+      expectUnreachable()
+    }
+  }
+}
+
+ErrorHandlingTests.test("tryOptional") {
+  expectEqual(LifetimeTracked(1), try? furball(false))
+  expectEqual(Optional<LifetimeTracked>.none, try? furball(true))
+}
+
+runAllTests()

test/SILGen/errors.swift

@@ -700,7 +700,8 @@ func testForcePeephole(f: () throws -> Int?) -> Int {
 // CHECK-NEXT: release_value [[RESULT]] : $Optional<Cat>
 // CHECK-NEXT: [[VOID:%.+]] = tuple ()
 // CHECK-NEXT: return [[VOID]] : $()
-// CHECK: [[FAILURE:.+]]({{%.+}} : $ErrorProtocol):
+// CHECK: [[FAILURE:.+]]([[ERROR:%.*]] : $ErrorProtocol):
+// CHECK-NEXT: strong_release [[ERROR]]
 // CHECK-NEXT: [[NONE:%.+]] = enum $Optional<Cat>, #Optional.none!enumelt
 // CHECK-NEXT: br [[DONE]]([[NONE]] : $Optional<Cat>)
 // CHECK: [[CLEANUPS]]([[ERROR:%.+]] : $ErrorProtocol):
@@ -725,7 +726,8 @@ func testOptionalTry() {
 // CHECK-NEXT: strong_release [[BOX]] : $@box Optional<Cat>
 // CHECK-NEXT: [[VOID:%.+]] = tuple ()
 // CHECK-NEXT: return [[VOID]] : $()
-// CHECK: [[FAILURE:.+]]({{%.+}} : $ErrorProtocol):
+// CHECK: [[FAILURE:.+]]([[ERROR:%.*]] : $ErrorProtocol):
+// CHECK-NEXT: strong_release [[ERROR]]
 // CHECK-NEXT: inject_enum_addr [[PB]] : $*Optional<Cat>, #Optional.none!enumelt
 // CHECK-NEXT: br [[DONE]]
 // CHECK: [[CLEANUPS]]([[ERROR:%.+]] : $ErrorProtocol):
@@ -753,7 +755,8 @@ func testOptionalTryVar() {
 // CHECK-NEXT: destroy_addr %0 : $*T
 // CHECK-NEXT: [[VOID:%.+]] = tuple ()
 // CHECK-NEXT: return [[VOID]] : $()
-// CHECK: [[FAILURE:.+]]({{%.+}} : $ErrorProtocol):
+// CHECK: [[FAILURE:.+]]([[ERROR:%.*]] : $ErrorProtocol):
+// CHECK-NEXT: strong_release [[ERROR]]
 // CHECK-NEXT: inject_enum_addr [[BOX]] : $*Optional<T>, #Optional.none!enumelt
 // CHECK-NEXT: br [[DONE]]
 // CHECK: [[CLEANUPS]]([[ERROR:%.+]] : $ErrorProtocol):
@@ -782,7 +785,8 @@ func testOptionalTryAddressOnly<T>(obj: T) {
 // CHECK-NEXT: destroy_addr %0 : $*T
 // CHECK-NEXT: [[VOID:%.+]] = tuple ()
 // CHECK-NEXT: return [[VOID]] : $()
-// CHECK: [[FAILURE:.+]]({{%.+}} : $ErrorProtocol):
+// CHECK: [[FAILURE:.+]]([[ERROR:%.*]] : $ErrorProtocol):
+// CHECK-NEXT: strong_release [[ERROR]]
 // CHECK-NEXT: inject_enum_addr [[PB]] : $*Optional<T>, #Optional.none!enumelt
 // CHECK-NEXT: br [[DONE]]
 // CHECK: [[CLEANUPS]]([[ERROR:%.+]] : $ErrorProtocol):
@@ -808,7 +812,8 @@ func testOptionalTryAddressOnlyVar<T>(obj: T) {
 // CHECK-NEXT: release_value [[RESULT]] : $Optional<(Cat, Cat)>
 // CHECK-NEXT: [[VOID:%.+]] = tuple ()
 // CHECK-NEXT: return [[VOID]] : $()
-// CHECK: [[FAILURE:.+]]({{%.+}} : $ErrorProtocol):
+// CHECK: [[FAILURE:.+]]([[ERROR:%.*]] : $ErrorProtocol):
+// CHECK-NEXT: strong_release [[ERROR]]
 // CHECK-NEXT: [[NONE:%.+]] = enum $Optional<(Cat, Cat)>, #Optional.none!enumelt
 // CHECK-NEXT: br [[DONE]]([[NONE]] : $Optional<(Cat, Cat)>)
 // CHECK: [[CLEANUPS_1]]([[ERROR:%.+]] : $ErrorProtocol):

test/SILOptimizer/definite_init_failable_initializers.swift

@@ -521,9 +521,10 @@ struct ThrowStruct {
 // CHECK-NEXT:    dealloc_stack [[SELF_BOX]]
 // CHECK-NEXT:    return [[NEW_SELF]] : $Optional<ThrowStruct>
 // CHECK:       bb6:
+// CHECK-NEXT:    strong_release [[ERROR:%.*]] : $ErrorProtocol
 // CHECK-NEXT:    [[NEW_SELF:%.*]] = enum $Optional<ThrowStruct>, #Optional.none!enumelt
 // CHECK-NEXT:    br bb2([[NEW_SELF]] : $Optional<ThrowStruct>)
-// CHECK:       bb7([[ERROR:%.*]] : $ErrorProtocol):
+// CHECK:       bb7([[ERROR]] : $ErrorProtocol):
 // CHECK-NEXT:    br bb6
   init?(throwsToOptional: Int) {
     try? self.init(failDuringDelegation: throwsToOptional)