[FIR2IR] Generate IR for f/o of common classes generated during platform conversion

This change fixes tests which were muted in one of previous commits

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrConverter.kt

@@ -116,6 +116,12 @@ class Fir2IrConverter(
             }
         }
 
+        if (components.session.languageVersionSettings.supportsFeature(LanguageFeature.MultiPlatformProjects)) {
+            // See the comment to generateUnboundFakeOverrides function itself
+            @OptIn(LeakedDeclarationCaches::class)
+            declarationStorage.generateUnboundFakeOverrides()
+        }
+
         evaluateConstants(irModuleFragment, components)
     }
 

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt

@@ -1141,6 +1141,61 @@ class Fir2IrDeclarationStorage(
         }
     }
 
+    // ------------------------------------ binding unbound symbols ------------------------------------
+
+    /**
+     * This function iterates over all f/o symbols created in declaration storage and binds all unbound symbols
+     *
+     * Usually all symbols are bound after fir2ir conversion is over, but there is a case in MPP scenario when some fake-override
+     *   for common classes appears only during conversion of platform session:
+     *
+     * // MODULE: common
+     * expect interface A
+     *
+     * interface B : A {
+     *     // f/o fun foo() // (1)
+     * }
+     *
+     * // MODULE: platform()()(common)
+     * actual interface A {
+     *     fun foo() // (2)
+     * }
+     *
+     * fun test(b: B) {
+     *     b.foo() // (3)
+     * }
+     *
+     * Here during common module conversion there is no `foo` function in scope of class B, so (1) is not generated
+     * During conversion of function test we reference symbol for (1) at line (3), so this symbol is created. But
+     *   there is no code which generate actual IR for this symbol, because IR for f/o is generated only during
+     *   conversion of corresponing class (and `B` is already converted)
+     *
+     * So to fix this issue we need to call this method after conversion of platform module
+     */
+    @LeakedDeclarationCaches
+    internal fun generateUnboundFakeOverrides() {
+        for ((identifier, symbol) in irForFirSessionDependantDeclarationMap) {
+            if (symbol.isBound) continue
+            val (originalSymbol, dispatchReceiverLookupTag, _) = identifier
+            val irParent = findIrParent(originalSymbol.fir, dispatchReceiverLookupTag)
+            when (originalSymbol) {
+                is FirPropertySymbol -> createAndCacheIrProperty(
+                    originalSymbol.fir,
+                    irParent,
+                    fakeOverrideOwnerLookupTag = dispatchReceiverLookupTag
+                )
+
+                is FirNamedFunctionSymbol -> createAndCacheIrFunction(
+                    originalSymbol.fir,
+                    irParent,
+                    fakeOverrideOwnerLookupTag = dispatchReceiverLookupTag
+                )
+
+                else -> error("Unexpected declaration: $originalSymbol")
+            }
+        }
+    }
+
     // ------------------------------------ scripts ------------------------------------
 
     fun getCachedIrScript(script: FirScript): IrScript? {

compiler/testData/codegen/box/multiplatform/hmpp/simple.kt

@@ -6,9 +6,6 @@
 // WITH_STDLIB
 // !LANGUAGE: +MultiPlatformProjects
 // IGNORE_CODEGEN_WITH_IR_FAKE_OVERRIDE_GENERATION: KT-62535
-// IGNORE_BACKEND_K2: JVM_IR
-//   Ignore reason: (TODO) how should generate IR for common f/o after actualization?
-
 // TARGET_BACKEND: JVM
 // MODULE: common
 // TARGET_PLATFORM: Common

compiler/testData/codegen/box/multiplatform/k2/basic/expectInterfaceInSupertypes.kt

@@ -3,9 +3,6 @@
 // WITH_STDLIB
 // !LANGUAGE: +MultiPlatformProjects
 // IGNORE_CODEGEN_WITH_IR_FAKE_OVERRIDE_GENERATION: KT-62535
-// IGNORE_BACKEND_K2: JVM_IR
-//   Ignore reason: (TODO) how should generate IR for common f/o after actualization?
-
 // MODULE: common
 // TARGET_PLATFORM: Common
 // FILE: common.kt

compiler/testData/codegen/box/multiplatform/k2/basic/expectInterfaceInSupertypes2.kt

@@ -3,8 +3,6 @@
 // WITH_STDLIB
 // IGNORE_CODEGEN_WITH_IR_FAKE_OVERRIDE_GENERATION: KT-62535
 // !LANGUAGE: +MultiPlatformProjects
-// IGNORE_BACKEND_K2: JVM_IR
-//   Ignore reason: (TODO) how should generate IR for common f/o after actualization?
 
 // MODULE: common
 // TARGET_PLATFORM: Common