Do not coerce function literals to suspend.

The design is to use `suspend fun` instead of coercion, just as suspend
lambdas.
However, this syntax is not supported in the parser. But this is not a
problem, since the coercion lead to internal compiler error.
As a workaround everybody uses suspend lambdas.
 #KT-24860: Fixed

compiler/testData/diagnostics/tests/inference/coerceFunctionLiteralToSuspend.kt

@@ -0,0 +1,29 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun fail1(c: suspend () -> Unit) {}
+
+fun fail2(c: () -> Unit) {}
+
+fun success1(c: suspend () -> Unit) {}
+
+fun test1() {
+    fail1(<!TYPE_MISMATCH!>fun () {}<!>)
+    fun fail2(c: suspend () -> Unit) {}
+    fail2(<!TYPE_MISMATCH!>fun () {}<!>)
+    fun success1(c: () -> Unit) {}
+    success1(fun() {})
+}
+
+suspend fun fail3(c: suspend () -> Unit) {}
+
+suspend fun fail4(c: () -> Unit) {}
+
+suspend fun success2(c: suspend () -> Unit) {}
+
+suspend fun test2() {
+    fail3(<!TYPE_MISMATCH!>fun () {}<!>)
+    fun fail4(c: suspend () -> Unit) {}
+    fail4(<!TYPE_MISMATCH!>fun () {}<!>)
+    fun success2(c: () -> Unit) {}
+    success2(fun() {})
+}

compiler/testData/diagnostics/tests/inference/coerceFunctionLiteralToSuspend.txt

@@ -0,0 +1,10 @@
+package
+
+public fun fail1(/*0*/ c: suspend () -> kotlin.Unit): kotlin.Unit
+public fun fail2(/*0*/ c: () -> kotlin.Unit): kotlin.Unit
+public suspend fun fail3(/*0*/ c: suspend () -> kotlin.Unit): kotlin.Unit
+public suspend fun fail4(/*0*/ c: () -> kotlin.Unit): kotlin.Unit
+public fun success1(/*0*/ c: suspend () -> kotlin.Unit): kotlin.Unit
+public suspend fun success2(/*0*/ c: suspend () -> kotlin.Unit): kotlin.Unit
+public fun test1(): kotlin.Unit
+public suspend fun test2(): kotlin.Unit

compiler/testData/diagnostics/tests/inference/lambdaInValInitializerWithAnonymousFunctions.kt

@@ -1,10 +1,9 @@
-// !WITH_NEW_INFERENCE
 typealias SuspendFn = suspend () -> Unit
 
-val test1f: suspend () -> Unit = fun () {}
-val test2f: suspend Any.() -> Unit = fun Any.() {}
+val test1f: suspend () -> Unit = <!TYPE_MISMATCH!>fun () {}<!>
+val test2f: suspend Any.() -> Unit = <!TYPE_MISMATCH!>fun Any.() {}<!>
 
 // This is a bug in the old inference and should be fixed in new inference
 // see "Fix anonymous function literals handling in type checker" for more deatils
-val test3f: suspend Any.(Int) -> Int = <!OI;TYPE_MISMATCH!>fun (k: Int) = k + 1<!>
-val test4f: SuspendFn = <!OI;TYPE_MISMATCH!>fun Any.() {}<!>
+val test3f: suspend Any.(Int) -> Int = <!TYPE_MISMATCH!>fun (k: Int) = k + 1<!>
+val test4f: SuspendFn = <!TYPE_MISMATCH!>fun Any.() {}<!>