Fix accessor generation for suspend functions

1. JVM view of suspend accessors must be also an instance of AccessorForFunctionDescriptor,
thus `createSubstitutedCopy` should be correctly overidden.

2. accessibleFunctionDescriptor should unwap the initial suspend descriptor,
for the same reasons as for type aliases constructors and etc:
these descriptors are used as keys of the map of accessors, so
to avoid duplication for suspend view and initial suspend descriptor,
we always use the latter one as a key.

 #KT-15907 Fixed
 #KT-15935 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/AccessorForFunctionDescriptor.java

@@ -20,6 +20,8 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.codegen.coroutines.CoroutineCodegenUtilKt;
 import org.jetbrains.kotlin.descriptors.*;
+import org.jetbrains.kotlin.descriptors.annotations.Annotations;
+import org.jetbrains.kotlin.descriptors.impl.FunctionDescriptorImpl;
 import org.jetbrains.kotlin.name.Name;
 import org.jetbrains.kotlin.resolve.DescriptorUtils;
 
@@ -28,6 +30,7 @@ import java.util.LinkedHashMap;
 public class AccessorForFunctionDescriptor extends AbstractAccessorForFunctionDescriptor implements AccessorForCallableDescriptor<FunctionDescriptor> {
     private final FunctionDescriptor calleeDescriptor;
     private final ClassDescriptor superCallTarget;
+    private final String nameSuffix;
 
     public AccessorForFunctionDescriptor(
             @NotNull FunctionDescriptor descriptor,
@@ -39,6 +42,7 @@ public class AccessorForFunctionDescriptor extends AbstractAccessorForFunctionDe
               Name.identifier("access$" + nameSuffix));
         this.calleeDescriptor = descriptor;
         this.superCallTarget = superCallTarget;
+        this.nameSuffix = nameSuffix;
 
         initialize(DescriptorUtils.getReceiverParameterType(descriptor.getExtensionReceiverParameter()),
                    descriptor instanceof ConstructorDescriptor || CodegenUtilKt.isJvmStaticInObjectOrClass(descriptor)
@@ -60,6 +64,19 @@ public class AccessorForFunctionDescriptor extends AbstractAccessorForFunctionDe
         }
     }
 
+    @NotNull
+    @Override
+    protected FunctionDescriptorImpl createSubstitutedCopy(
+            @NotNull DeclarationDescriptor newOwner,
+            @Nullable FunctionDescriptor original,
+            @NotNull Kind kind,
+            @Nullable Name newName,
+            @NotNull Annotations annotations,
+            @NotNull SourceElement source
+    ) {
+        return new AccessorForFunctionDescriptor(calleeDescriptor, newOwner, superCallTarget, nameSuffix);
+    }
+
     @NotNull
     @Override
     public FunctionDescriptor getCalleeDescriptor() {

compiler/backend/src/org/jetbrains/kotlin/codegen/ExpressionCodegen.java

@@ -2732,6 +2732,9 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
         if (originalIfSamAdapter != null) {
             descriptor = originalIfSamAdapter;
         }
+
+        descriptor = CoroutineCodegenUtilKt.unwrapInitialDescriptorForSuspendFunction(descriptor);
+
         // $default method is not private, so you need no accessor to call it
         return CallUtilKt.usesDefaultArguments(resolvedCall)
                ? descriptor