Improve determining which C enum constants are explicitly defined (#3384)

Improve determining which C enum constants are explicitly defined

Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/Indexer.kt

@@ -276,7 +276,7 @@ internal class NativeIndexImpl(val library: NativeLibrary, val verbose: Boolean
                     val name = clang_getCursorSpelling(childCursor).convertAndDispose()
                     val value = clang_getEnumConstantDeclValue(childCursor)
 
-                    val constant = EnumConstant(name, value, isExplicitlyDefined = !childCursor.isLeaf())
+                    val constant = EnumConstant(name, value, isExplicitlyDefined = childCursor.hasExpressionChild())
                     enumDef.constants.add(constant)
                 }
 

Interop/Indexer/src/main/kotlin/org/jetbrains/kotlin/native/interop/indexer/Utils.kt

@@ -201,15 +201,19 @@ fun StructDef.fieldsHaveDefaultAlignment(): Boolean {
     return true
 }
 
-internal fun CValue<CXCursor>.isLeaf(): Boolean {
-    var hasChildren = false
+internal fun CValue<CXCursor>.hasExpressionChild(): Boolean {
+    var result = false
 
-    visitChildren(this) { _, _ ->
-        hasChildren = true
-        CXChildVisitResult.CXChildVisit_Break
+    visitChildren(this) { cursor, _ ->
+        if (clang_isExpression(cursor.kind) != 0) {
+            result = true
+            CXChildVisitResult.CXChildVisit_Break
+        } else {
+            CXChildVisitResult.CXChildVisit_Continue
+        }
     }
 
-    return !hasChildren
+    return result
 }
 
 internal fun List<String>.toNativeStringArray(scope: AutofreeScope): CArrayPointer<CPointerVar<ByteVar>> {

backend.native/tests/interop/basics/ctypes.def

@@ -48,4 +48,25 @@ static int vlaSum2DBothDimensions(int rows, int columns, int array[rows][columns
 static int vlaSum2DForward(int size; int array[][size], int size) {
     return vlaSum2D(size, array);
 }
-*/
+*/
+
+// "Strict" enums heuristic based on whether enum constants are defined explicitly:
+enum StrictEnum1 {
+    StrictEnum1A,
+    StrictEnum1B
+};
+
+enum StrictEnum2 {
+    StrictEnum2A __attribute__((unused)),
+    StrictEnum2B __attribute__((unused))
+};
+
+enum NonStrictEnum1 {
+    NonStrictEnum1A = 0,
+    NonStrictEnum1B __attribute__((unused))
+};
+
+enum NonStrictEnum2 {
+    NonStrictEnum2A,
+    NonStrictEnum2B __attribute__((unused)) = 1
+};

backend.native/tests/interop/basics/types.kt

@@ -16,4 +16,9 @@ fun main() {
 
     // Not supported by clang:
     // assertEquals(10, vlaSum2DForward(cValuesOf(1, 2, 3, 4), 2))
+
+    assertEquals(0u, StrictEnum1.StrictEnum1A.value)
+    assertEquals(1u, StrictEnum2.StrictEnum2B.value)
+    assertEquals(0u, NonStrictEnum1A)
+    assertEquals(1u, NonStrictEnum2B)
 }