Add SIL verification to ensure we don't return local addresses

lib/SIL/Verifier/SILVerifier.cpp

@@ -5359,6 +5359,17 @@ public:
                instResultType.dump(););
     requireSameType(functionResultType, instResultType,
                     "return value type does not match return type of function");
+
+    // If the result type is an address, ensure it's base address is from a
+    // function argument.
+    if (F.getModule().getStage() >= SILStage::Canonical &&
+        functionResultType.isAddress()) {
+      auto base = getAccessBase(RI->getOperand());
+      require(!base->getType().isAddress() || isa<SILFunctionArgument>(base) ||
+                  isa<ApplyInst>(base) &&
+                      cast<ApplyInst>(base)->hasAddressResult(),
+              "unidentified address return");
+    }
   }
 
   void checkThrowInst(ThrowInst *TI) {

test/SIL/borrow_accessor_verify_errors.sil

@@ -0,0 +1,32 @@
+// RUN: %target-sil-opt -dont-abort-on-memory-lifetime-errors -verify-continue-on-failure -enable-sil-verify-all=0 %s 2>&1 | %FileCheck %s
+
+sil_stage canonical
+
+public struct GenWrapper<T> {
+  @_hasStorage var _prop: T { get set }
+  public var prop: T
+}
+
+sil [ossa] @borrow_addressonly_prop : $@convention(method) <T> (@in_guaranteed GenWrapper<T>) -> @guaranteed_address T {
+bb0(%0 : $*GenWrapper<T>):
+  %2 = struct_element_addr %0, #GenWrapper._prop
+  return %2
+}
+
+// CHECK: Begin Error in function test_address_of_temp
+// CHECK: SIL verification failed: unidentified address return: !base->getType().isAddress() || isa<SILFunctionArgument>(base) || isa<ApplyInst>(base) && cast<ApplyInst>(base)->hasAddressResult()
+// CHECK: Verifying instruction:
+// CHECK:      %4 = apply %3<T>(%1) : $@convention(method) <τ_0_0> (@in_guaranteed GenWrapper<τ_0_0>) -> @guaranteed_address τ_0_0
+// CHECK: ->   return %4 : $*T
+// CHECK: End Error in function test_address_of_temp
+sil [ossa] @test_address_of_temp : $@convention(thin) <T> (@in_guaranteed GenWrapper<T>) -> @guaranteed_address T {
+bb0(%0 : $*GenWrapper<T>):
+  %stk = alloc_stack $GenWrapper<T>
+  copy_addr %0 to [init] %stk
+  %1 = function_ref @borrow_addressonly_prop : $@convention(method) <τ_0_0> (@in_guaranteed GenWrapper<τ_0_0>) -> @guaranteed_address τ_0_0
+  %2 = apply %1<T>(%stk) : $@convention(method) <τ_0_0> (@in_guaranteed GenWrapper<τ_0_0>) -> @guaranteed_address τ_0_0
+  destroy_addr %stk
+  dealloc_stack %stk
+  return %2
+}
+

test/SILGen/borrow_accessor_failues.swift

@@ -1,4 +1,4 @@
-// RUN:%target-swift-frontend -emit-silgen %s -verify  -enable-experimental-feature BorrowAndMutateAccessors
+// RUN:%target-swift-frontend -emit-silgen %s -enable-experimental-feature BorrowAndMutateAccessors -sil-verify-none -verify
 
 // REQUIRES: swift_feature_BorrowAndMutateAccessors