Fix "redundant async" for coroutines 1.*, forbid explicit scopes case

Related to KT-28504
#KT-28445 Fixed

idea/testData/inspectionsLocal/coroutines/redundantAsync/coroutines.lib.kt

@@ -6,7 +6,9 @@ interface Deferred<T> {
 
 interface CoroutineContext
 
-object DefaultDispatcher : CoroutineContext
+object Dispatchers {
+    object Default : CoroutineContext
+}
 
 enum class CoroutineStart {
     DEFAULT,
@@ -15,30 +17,28 @@ enum class CoroutineStart {
     UNDISPATCHED
 }
 
-interface Job
-
-fun <T> async(
-    context: CoroutineContext = DefaultDispatcher,
-    start: CoroutineStart = CoroutineStart.DEFAULT,
-    parent: Job? = null,
-    f: suspend () -> T
-): Deferred<T> {
-    TODO()
+interface CoroutineScope {
+    val coroutineContext: CoroutineContext get() = Dispatchers.Default
 }
 
-fun <T> runBlocking(
-    context: CoroutineContext = DefaultDispatcher,
-    f: suspend () -> T
-) {
+object GlobalScope : CoroutineScope
+
+fun <T> CoroutineScope.async(
+    context: CoroutineContext = Dispatchers.Default,
+    start: CoroutineStart = CoroutineStart.DEFAULT,
+    block: suspend CoroutineScope.() -> T
+): Deferred<T> {
     TODO()
 }
 
 suspend fun <T> withContext(
     context: CoroutineContext,
     start: CoroutineStart = CoroutineStart.DEFAULT,
-    f: suspend () -> T
+    block: suspend CoroutineScope.() -> T
 ) {
     TODO()
 }
 
+suspend fun <R> coroutineScope(block: suspend CoroutineScope.() -> R): R = GlobalScope.block()
+
 

idea/testData/inspectionsLocal/coroutines/redundantAsync/explicitScope.kt

@@ -0,0 +1,9 @@
+// WITH_RUNTIME
+// PROBLEM: none
+
+package kotlinx.coroutines
+
+suspend fun test(ctx: CoroutineContext, scope: CoroutineScope) {
+    // Does not work yet (1.3.11)
+    scope.<caret>async(ctx) { 42 }.await()
+}

idea/testData/inspectionsLocal/coroutines/redundantAsync/globalScope.kt

@@ -1,8 +1,9 @@
-// PROBLEM: none
 // WITH_RUNTIME
+// PROBLEM: none
 
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    <caret>async(parent = null) { 42 }.await()
+    // Does not work yet (1.3.11)
+    GlobalScope.<caret>async(ctx) { 42 }.await()
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/simple.kt

@@ -4,5 +4,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    <caret>async(ctx) { 42 }.await()
+    coroutineScope {
+        <caret>async(ctx) { 42 }.await()
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/simple.kt.after

@@ -4,5 +4,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    withContext(ctx) { 42 }
+    coroutineScope {
+        withContext(ctx) { 42 }
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/simplest.kt

@@ -1,8 +1,10 @@
 // WITH_RUNTIME
-// FIX: Merge call chain to 'withContext(DefaultDispatcher)'
+// FIX: Merge call chain to 'withContext(Default)'
 
 package kotlinx.coroutines
 
 suspend fun test() {
-    <caret>async { 42 }.await()
+    coroutineScope {
+        <caret>async { 42 }.await()
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/simplest.kt.after

@@ -1,8 +1,10 @@
 // WITH_RUNTIME
-// FIX: Merge call chain to 'withContext(DefaultDispatcher)'
+// FIX: Merge call chain to 'withContext(Default)'
 
 package kotlinx.coroutines
 
 suspend fun test() {
-    withContext(DefaultDispatcher) { 42 }
+    coroutineScope {
+        withContext(Dispatchers.Default) { 42 }
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/withStartAndContext.kt

@@ -3,5 +3,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    <caret>async(ctx, CoroutineStart.LAZY) { 42 }.await()
+    coroutineScope {
+        <caret>async(ctx, CoroutineStart.LAZY) { 42 }.await()
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/withStartAndContext.kt.after

@@ -3,5 +3,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    withContext(ctx, CoroutineStart.LAZY) { 42 }
+    coroutineScope {
+        withContext(ctx, CoroutineStart.LAZY) { 42 }
+    }
 }

idea/testData/inspectionsLocal/coroutines/redundantAsync/withStartNoContext.kt

@@ -4,5 +4,7 @@
 package kotlinx.coroutines
 
 suspend fun test(ctx: CoroutineContext) {
-    <caret>async(start = CoroutineStart.LAZY) { 42 }.await()
+    coroutineScope {
+        <caret>async(start = CoroutineStart.LAZY) { 42 }.await()
+    }
 }