SR-12802: Disambiguate functions with lvalue and rvalue reference parameters in the same overload set

Author: cabmeurer

lib/ClangImporter/ImportType.cpp

@@ -2291,9 +2291,11 @@ ParameterList *ClangImporter::Implementation::importFunctionParameterList(
         return nullptr;
       }
 
-      paramTy = refType->getPointeeType();
-      if (!paramTy.isConstQualified())
-        isInOut = true;
+        paramTy = refType->getPointeeType();
+        if (isa<clang::LValueReferenceType>(paramTy)
+            && !paramTy.isConstQualified()) {
+            isInOut = true;
+        }
     }
 
     if (!swiftParamTy) {

lib/SIL/IR/SILFunctionType.cpp

@@ -1327,9 +1327,12 @@ static bool isClangTypeMoreIndirectThanSubstType(TypeConverter &TC,
   // Pass C++ const reference types indirectly. Right now there's no way to
   // express immutable borrowed params, so we have to have this hack.
   // Eventually, we should just express these correctly: rdar://89647503
-  if (clangTy->isReferenceType() &&
-      clangTy->getPointeeType().isConstQualified())
-    return true;
+    if (clangTy->isReferenceType()) {
+        if (clangTy->isRValueReferenceType() ||
+            clangTy->getPointeeType().isConstQualified()) {
+            return true;
+        }
+    }
 
   return false;
 }

test/Interop/Cxx/stdlib/use-std-iterator.swift

@@ -13,10 +13,9 @@ var StdIteratorTestSuite = TestSuite("StdIterator")
 
 StdIteratorTestSuite.test("init") {
     var vector = Vector()
-    var _1: CInt = 1
     //There seems to be an issue when importing this method, where the const_ref is mapped with 
     //the correct typealias to be able to pass immutable values. related to: https://github.com/apple/swift/pull/41611
-    vector.push_back(&_1)
+    vector.push_back(1)
     //ideally we should call vector.begin(), however we need to prevent a copy of self before vector.begin() is invoked
     //current workaround is to use beginMutating()
     let it = vector.beginMutating()
@@ -25,10 +24,9 @@ StdIteratorTestSuite.test("init") {
 
 StdIteratorTestSuite.test("advance") {
     var vector = Vector()
-    var _1: CInt = 1, _2: CInt = 2, _3: CInt = 3
-    vector.push_back(&_1)
-    vector.push_back(&_2)
-    vector.push_back(&_3)
+    vector.push_back(1)
+    vector.push_back(2)
+    vector.push_back(3)
     var it = vector.beginMutating()
     std.__1.advance(&it, 2)
     expectEqual(it[0], 3)

test/Interop/Cxx/stdlib/use-std-vector.swift

@@ -24,18 +24,16 @@ StdVectorTestSuite.test("init") {
 
 StdVectorTestSuite.test("push back") {
     var v = Vector()
-    var _42: CInt = 42
-    v.push_back(&_42)
+    v.push_back(42)
     expectEqual(v.size(), 1)
     expectFalse(v.empty())
     expectEqual(v[0], 42)
 }
 
 func fill(vector v: inout Vector) {
-    var _1: CInt = 1, _2: CInt = 2, _3: CInt = 3
-    v.push_back(&_1)
-    v.push_back(&_2)
-    v.push_back(&_3)
+    v.push_back(1)
+    v.push_back(2)
+    v.push_back(3)
 }
 
 // TODO: in some configurations the stdlib emits a "initializeWithCopy" where the arguments