Add base declaration checker for fun interfaces

compiler/testData/diagnostics/tests/funInterface/funInterfaceDeclarationCheck.fir.kt

@@ -0,0 +1,104 @@
+// !LANGUAGE: +FunctionalInterfaceConversion
+
+fun interface Good {
+    fun invoke()
+}
+
+fun interface Foo1
+
+fun interface Foo2 {
+
+}
+
+fun interface Foo3 {
+    fun foo()
+    fun bar()
+}
+
+interface BaseWithSAM {
+    fun base()
+}
+
+fun interface Foo4 : BaseWithSAM {
+    fun oneMore()
+}
+
+fun interface Foo4WithDefault : BaseWithSAM {
+    fun oneMore() {}
+}
+
+interface BaseWithDefault {
+    fun def() {}
+}
+
+fun interface Foo4WithBaseDefault : BaseWithDefault {
+    fun oneMore()
+}
+
+fun interface GoodWithBase : BaseWithSAM
+
+fun interface Foo5 {
+    val prop: Int
+}
+
+fun interface Foo6 {
+    fun foo()
+    val prop: Int
+}
+
+fun interface Foo7 : BaseWithSAM {
+    val prop: Int
+}
+
+fun interface GoodWithPropAndBase : BaseWithSAM {
+    val prop: Int get() = 42
+}
+
+fun interface Foo8 {
+    fun <T> invoke(x: T)
+}
+
+fun interface GoodGeneric<T> {
+    fun invoke(x: T)
+}
+
+interface BaseWithGeneric {
+    fun <T> invoke(x: T)
+}
+
+fun interface Foo9 : BaseWithGeneric
+
+fun interface GoodExtensionGeneric : GoodGeneric<String>
+
+fun interface GoodSuspend {
+    suspend fun invoke()
+}
+
+class WithNestedFun<K> {
+    fun interface NestedSimple
+
+    fun interface GoodFun {
+        fun invoke()
+    }
+
+    fun interface NestedFun {
+        fun inovke(element: K)
+    }
+}
+
+fun <T> local() {
+    fun interface LocalFun {
+        fun invoke(element: T)
+    }
+}
+
+fun interface WithDefaultValue {
+    fun invoke(s: String = "")
+}
+
+interface BaseWithDefaultValue {
+    fun invoke(s: String = "")
+}
+
+fun interface DeriveDefault : BaseWithDefaultValue
+