only stub default constructor when compiling against .java source files

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaSymbolProvider.kt

@@ -250,7 +250,9 @@ class JavaSymbolProvider(
                         }
                     }
 
-                    if (javaClassDeclaredConstructors.isEmpty() && javaClass.classKind == ClassKind.CLASS) {
+                    if (javaClassDeclaredConstructors.isEmpty()
+                        && javaClass.classKind == ClassKind.CLASS
+                        && javaClass.hasDefaultConstructor()) {
                         declarations += prepareJavaConstructor(isPrimary = true).build()
                     }
                     for (javaConstructor in javaClassDeclaredConstructors) {

compiler/frontend.java/src/org/jetbrains/kotlin/load/java/structure/impl/JavaClassImpl.kt

@@ -100,6 +100,8 @@ class JavaClassImpl(psiClass: PsiClass) : JavaClassifierImpl<PsiClass>(psiClass)
             return constructors(psi.constructors.filter { method -> method.isConstructor })
         }
 
+    override fun hasDefaultConstructor() = !isInterface && constructors.isEmpty()
+
     override val isAbstract: Boolean
         get() = JavaElementUtil.isAbstract(this)
 

compiler/frontend.java/src/org/jetbrains/kotlin/load/java/structure/impl/classFiles/BinaryJavaClass.kt

@@ -47,6 +47,7 @@ class BinaryJavaClass(
     override val methods = arrayListOf<JavaMethod>()
     override val fields = arrayListOf<JavaField>()
     override val constructors = arrayListOf<JavaConstructor>()
+    override fun hasDefaultConstructor() = false // never: all constructors explicit in bytecode
 
     override val annotationsByFqName by buildLazyValueForMap()
 

compiler/javac-wrapper/src/org/jetbrains/kotlin/javac/resolve/KotlinClassifiersCache.kt

@@ -159,6 +159,7 @@ class MockKotlinClassifier(override val classId: ClassId,
     override val methods get() = shouldNotBeCalled()
     override val fields get() = shouldNotBeCalled()
     override val constructors get() = shouldNotBeCalled()
+    override fun hasDefaultConstructor() = shouldNotBeCalled()
     override val annotations get() = shouldNotBeCalled()
     override val isDeprecatedInJavaDoc get() = shouldNotBeCalled()
     override fun findAnnotation(fqName: FqName) = shouldNotBeCalled()

compiler/javac-wrapper/src/org/jetbrains/kotlin/javac/wrappers/symbols/FakeSymbolBasedClass.kt

@@ -73,6 +73,8 @@ class FakeSymbolBasedClass(
 
     override val constructors: Collection<JavaConstructor> get() = emptyList()
 
+    override fun hasDefaultConstructor() = false
+
     override val innerClassNames: Collection<Name> get() = emptyList()
 
     override val virtualFile: VirtualFile? by lazy {

compiler/javac-wrapper/src/org/jetbrains/kotlin/javac/wrappers/symbols/SymbolBasedClass.kt

@@ -133,6 +133,8 @@ class SymbolBasedClass(
             .filter { it.kind == ElementKind.CONSTRUCTOR }
             .map { SymbolBasedConstructor(it as ExecutableElement, this, javac) }
 
+    override fun hasDefaultConstructor() = false // default constructors are explicit in symbols
+
     override val innerClassNames: Collection<Name>
         get() = innerClasses.keys
 

compiler/javac-wrapper/src/org/jetbrains/kotlin/javac/wrappers/trees/TreeBasedClass.kt

@@ -134,6 +134,8 @@ class TreeBasedClass(
                     TreeBasedConstructor(constructor as JCTree.JCMethodDecl, compilationUnit, this, javac)
                 }
 
+    override fun hasDefaultConstructor() = !isInterface && constructors.isEmpty()
+
     override val innerClassNames: Collection<Name>
         get() = innerClasses.keys
 

compiler/testData/compileKotlinAgainstCustomBinaries/classfileWithoutConstructors/TopLevel.kt

@@ -0,0 +1,3 @@
+package test
+
+fun foo(msg: String) = msg

compiler/testData/compileKotlinAgainstCustomBinaries/classfileWithoutConstructors/TopLevel.txt

@@ -0,0 +1 @@
+OK

compiler/testData/compileKotlinAgainstCustomBinaries/classfileWithoutConstructors/output.txt

@@ -0,0 +1,4 @@
+compiler/testData/compileKotlinAgainstCustomBinaries/classfileWithoutConstructors/shouldNotCompile.kt:6:9: error: unresolved reference: TopLevelKt
+        TopLevelKt() // error here
+        ^
+COMPILATION_ERROR

compiler/testData/compileKotlinAgainstCustomBinaries/classfileWithoutConstructors/shouldNotCompile.kt

@@ -0,0 +1,10 @@
+package test
+
+public class B {
+
+    public fun test(): String {
+        TopLevelKt() // error here
+        return TopLevelKt.foo("OK") // no error here: can still call static functions
+    }
+
+}

compiler/testData/compileKotlinAgainstJava/ClassDefaultConstructor.java

@@ -0,0 +1,4 @@
+package test;
+
+public class ClassDefaultConstructor {
+}

compiler/testData/compileKotlinAgainstJava/ClassDefaultConstructor.kt

@@ -0,0 +1,3 @@
+package test
+
+fun useClassDefaultConstructor() = ClassDefaultConstructor()

compiler/testData/compileKotlinAgainstJava/ClassDefaultConstructor.txt

@@ -0,0 +1,7 @@
+package test
+
+public fun useClassDefaultConstructor(): test.ClassDefaultConstructor
+
+public open class ClassDefaultConstructor {
+    public constructor ClassDefaultConstructor()
+}

compiler/tests/org/jetbrains/kotlin/jvm/compiler/CompileKotlinAgainstCustomBinariesTest.kt

@@ -458,6 +458,37 @@ class CompileKotlinAgainstCustomBinariesTest : AbstractKotlinCompilerIntegration
         }
     }
 
+    /* Regression test for KT-37107: compile against .class file without any constructors. */
+    fun testClassfileWithoutConstructors() {
+        compileKotlin("TopLevel.kt", tmpdir, expectedFileName = "TopLevel.txt")
+
+        val inlineFunClass = File(tmpdir.absolutePath, "test/TopLevelKt.class")
+        val cw = ClassWriter(Opcodes.API_VERSION)
+        ClassReader(inlineFunClass.readBytes()).accept(object : ClassVisitor(Opcodes.API_VERSION, cw) {
+            override fun visitAnnotation(desc: String, visible: Boolean): AnnotationVisitor? =
+                if (desc == JvmAnnotationNames.METADATA_DESC) null else super.visitAnnotation(desc, visible)
+
+            override fun visitMethod(
+                access: Int,
+                name: String?,
+                descriptor: String?,
+                signature: String?,
+                exceptions: Array<out String>?
+            ): MethodVisitor {
+                assertEquals("foo", name) // test sanity: shouldn't see any constructors, only the "foo" method
+                return super.visitMethod(access, name, descriptor, signature, exceptions)
+            }
+        }, 0)
+
+        assert(inlineFunClass.delete())
+        assert(!inlineFunClass.exists())
+
+        inlineFunClass.writeBytes(cw.toByteArray())
+
+        val (_, exitCode) = compileKotlin("shouldNotCompile.kt", tmpdir, listOf(tmpdir))
+        assertEquals(1, exitCode.code) // double-check that we failed :) output.txt also says so
+    }
+
     fun testReplaceAnnotationClassWithInterface() {
         val library1 = compileLibrary("library-1")
         val usage = compileLibrary("usage", extraClassPath = listOf(library1))

compiler/tests/org/jetbrains/kotlin/jvm/compiler/CompileKotlinAgainstJavaTestGenerated.java

@@ -70,6 +70,11 @@ public class CompileKotlinAgainstJavaTestGenerated extends AbstractCompileKotlin
             runTest("compiler/testData/compileKotlinAgainstJava/Class.kt");
         }
 
+        @TestMetadata("ClassDefaultConstructor.kt")
+        public void testClassDefaultConstructor() throws Exception {
+            runTest("compiler/testData/compileKotlinAgainstJava/ClassDefaultConstructor.kt");
+        }
+
         @TestMetadata("ClassWithNestedEnum.kt")
         public void testClassWithNestedEnum() throws Exception {
             runTest("compiler/testData/compileKotlinAgainstJava/ClassWithNestedEnum.kt");
@@ -353,6 +358,11 @@ public class CompileKotlinAgainstJavaTestGenerated extends AbstractCompileKotlin
             runTest("compiler/testData/compileKotlinAgainstJava/Class.kt");
         }
 
+        @TestMetadata("ClassDefaultConstructor.kt")
+        public void testClassDefaultConstructor() throws Exception {
+            runTest("compiler/testData/compileKotlinAgainstJava/ClassDefaultConstructor.kt");
+        }
+
         @TestMetadata("ClassWithNestedEnum.kt")
         public void testClassWithNestedEnum() throws Exception {
             runTest("compiler/testData/compileKotlinAgainstJava/ClassWithNestedEnum.kt");

core/descriptors.jvm/src/org/jetbrains/kotlin/load/java/lazy/descriptors/LazyJavaClassMemberScope.kt

@@ -619,7 +619,7 @@ class LazyJavaClassMemberScope(
 
     private fun createDefaultConstructor(): ClassConstructorDescriptor? {
         val isAnnotation: Boolean = jClass.isAnnotationType
-        if (jClass.isInterface && !isAnnotation)
+        if ((jClass.isInterface || !jClass.hasDefaultConstructor()) && !isAnnotation)
             return null
 
         val classDescriptor = ownerDescriptor

core/descriptors.jvm/src/org/jetbrains/kotlin/load/java/structure/javaElements.kt

@@ -90,6 +90,7 @@ interface JavaClass : JavaClassifier, JavaTypeParameterListOwner, JavaModifierLi
     val methods: Collection<JavaMethod>
     val fields: Collection<JavaField>
     val constructors: Collection<JavaConstructor>
+    fun hasDefaultConstructor(): Boolean
 }
 
 val JavaClass.classId: ClassId?

core/descriptors.runtime/src/org/jetbrains/kotlin/descriptors/runtime/structure/ReflectJavaClass.kt

@@ -96,6 +96,8 @@ class ReflectJavaClass(
             .map(::ReflectJavaConstructor)
             .toList()
 
+    override fun hasDefaultConstructor() = false // any default constructor is returned by constructors
+
     override val lightClassOriginKind: LightClassOriginKind?
         get() = null