Don't make unnecessary NULL unboxings

Author: AlexVanGogen

IntelliJ-patches.md

@@ -75,7 +75,7 @@ Some logic related to instrumentation was extracted to separate methods so that
 - `kotlinx.coroutines.flow.internal.FlowValueWrapperInternalKt.unwrapInternalDebuggerCapture` -- unwraps passed argument so it returns the original value; only used after transformation
 - `kotlinx.coroutines.flow.internal.FlowValueWrapperInternalKt.unwrapTyped` -- utility function served to ease casting to a real underlying type
 - `kotlinx.coroutines.flow.internal.FlowValueWrapperInternalKt.emitInternal(FlowCollector, value)` -- alternative of a regular `FlowCollector.emit` that supports insertion points; if there is a `FlowCollector`, its `emit` call can be replaced with `emitInternal` so this case would also be supported for constructing async stack traces 
-- `kotlinx.coroutines.flow.internal.FlowValueWrapperInternalKt.debuggerCapture` -- common insertion point for a debugger agent; simplifies instrumentation; the value is always being unwrapped inside. `emitInternal` uses this method.
+- `kotlinx.coroutines.flow.internal.FlowValueWrapperInternalKt.debuggerCapture` -- common insertion point for a debugger agent; simplifies instrumentation; the value is always being unwrapped inside.
 
 One internal method was added to `BufferedChannel`: `emitAllInternal`. This method ensures the value will be unwrapped in an insertion point.
 

kotlinx-coroutines-core/common/src/channels/BufferedChannel.kt

@@ -1543,7 +1543,7 @@ internal open class BufferedChannel<E>(
     @Suppress("UNCHECKED_CAST")
     private val onUndeliveredElementReceiveCancellationConstructor: OnCancellationConstructor? = onUndeliveredElement?.let {
         { select: SelectInstance<*>, _: Any?, element: Any? ->
-            { if (element !== CHANNEL_CLOSED) onUndeliveredElement.callUndeliveredElement(element as E, select.context) }
+            { if (element !== CHANNEL_CLOSED) onUndeliveredElement.callUndeliveredElement(unwrapTyped(element), select.context) }
         }
     }
 

kotlinx-coroutines-core/common/src/flow/internal/FlowValueWrapperInternal.kt

@@ -36,10 +36,10 @@ private fun unwrapInternalDebuggerCapture(value: Any?): Any? {
 
 // Shouldn't be inlined, the method is instrumented by the IDEA debugger agent
 internal suspend fun <T> FlowCollector<T>.emitInternal(value: Any?) {
-    debuggerCapture<T, Unit>(value) { emit(it) }
+    emit(unwrapTyped<T>(value))
 }
 
 // Shouldn't be inlined, the method is instrumented by the IDEA debugger agent
 internal suspend fun <Unwrapped, R> debuggerCapture(value: Any?, block: suspend (Unwrapped) -> R): R {
-    return block(unwrapTyped<Unwrapped>(value))
+    return block(unwrapInternal(value) as Unwrapped)
 }