Allow calling some pieces of the experimental coroutine API

- Calling suspend functions is allowed
- Presence of suspend function type still makes declaration
unusable unless it belongs to a value parameter as a top-level type
containing less then three parameters

Still, warning should be emitted because they will become unsupported in 1.4

 #KT-25683 In Progress

compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/library/experimental.kt

@@ -1,27 +1,14 @@
-suspend fun dummy() {}
-
-class C {
-    suspend fun dummy() = "OK"
-}
-
-class WithNested {
-    class Nested {
-        suspend fun dummy() = "OK"
-    }
-}
-
-class WithInner {
-    inner class Inner {
-        suspend fun dummy() = "OK"
-    }
-}
-
 val c: suspend () -> Unit = {}
 
 class WithTypeParameter<T: suspend() -> Unit> {}
 
 fun returnsSuspend() : suspend() -> Unit = {}
 
-fun builder(c: suspend () -> Unit) {}
+fun <T: suspend () -> Unit> withTypeParameter() = {}
 
-fun <T: suspend () -> Unit> withTypeParameter() = {}
+fun suspendFunctionNested(x: List<suspend () -> Unit>) {}
+fun suspendFunctionNestedInFunctionType(x: (suspend () -> Unit) -> Unit) {}
+
+fun suspendFunctionType3(x: suspend (Int, Int, Int) -> Unit) {}
+
+fun suspendVarargs(vararg x: suspend () -> Unit) {}

compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/output.txt

@@ -1,29 +1,30 @@
 warning: language version 1.3 is experimental, there are no backwards compatibility guarantees for new language and library features
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:2:5: error: using 'c: suspend () -> Unit' is an error. Experimental coroutine cannot be used with API version 1.3
-    c()
-    ^
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:3:5: error: using 'constructor WithTypeParameter<T : suspend () -> Unit>()' is an error. Experimental coroutine cannot be used with API version 1.3
+warning: runtime JAR files in the classpath should have the same version. These files were found in the classpath:
+    $DIST_DIR$/kotlin-stdlib-coroutines.jar (version 1.3)
+    $PROJECT_DIR$/lib/kotlin-stdlib.jar (version 1.2)
+    $PROJECT_DIR$/lib/kotlin-script-runtime.jar (version 1.2)
+    $PROJECT_DIR$/lib/kotlin-reflect.jar (version 1.2)
+warning: consider providing an explicit dependency on kotlin-reflect 1.3 to prevent strange errors
+warning: some runtime JAR files in the classpath have an incompatible version. Consider removing them from the classpath
+compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:2:5: error: using 'constructor WithTypeParameter<T : suspend () -> Unit>()' is an error. Experimental coroutine cannot be used with API version 1.3
     WithTypeParameter<suspend () -> Unit>()
     ^
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:4:5: error: using 'returnsSuspend(): suspend () -> Unit' is an error. Experimental coroutine cannot be used with API version 1.3
+compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:3:5: error: using 'returnsSuspend(): suspend () -> Unit' is an error. Experimental coroutine cannot be used with API version 1.3
     returnsSuspend()
     ^
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:5:5: error: using 'builder(suspend () -> Unit): Unit' is an error. Experimental coroutine cannot be used with API version 1.3
-    builder {}
-    ^
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:6:5: error: using 'withTypeParameter(): () -> Unit' is an error. Experimental coroutine cannot be used with API version 1.3
+compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:4:5: error: using 'withTypeParameter(): () -> Unit' is an error. Experimental coroutine cannot be used with API version 1.3
     withTypeParameter<suspend () -> Unit>()
     ^
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:8:5: error: using 'dummy(): Unit' is an error. Experimental coroutine cannot be used with API version 1.3
-    dummy()
+compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:6:5: error: using 'suspendFunctionNested(List<suspend () -> Unit>): Unit' is an error. Experimental coroutine cannot be used with API version 1.3
+    suspendFunctionNested(listOf(suspend {  }))
+    ^
+compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:7:5: error: using 'suspendFunctionNestedInFunctionType((suspend () -> Unit) -> Unit): Unit' is an error. Experimental coroutine cannot be used with API version 1.3
+    suspendFunctionNestedInFunctionType {}
+    ^
+compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:8:5: error: using 'suspendFunctionType3(suspend (Int, Int, Int) -> Unit): Unit' is an error. Experimental coroutine cannot be used with API version 1.3
+    suspendFunctionType3 { x, y, z -> }
+    ^
+compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:10:5: error: using 'suspendVarargs(vararg suspend () -> Unit): Unit' is an error. Experimental coroutine cannot be used with API version 1.3
+    suspendVarargs({}, {})
     ^
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:9:9: error: using 'dummy(): String' is an error. Experimental coroutine cannot be used with API version 1.3
-    C().dummy()
-        ^
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:10:25: error: using 'dummy(): String' is an error. Experimental coroutine cannot be used with API version 1.3
-    WithNested.Nested().dummy()
-                        ^
-compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt:11:25: error: using 'dummy(): String' is an error. Experimental coroutine cannot be used with API version 1.3
-    WithInner().Inner().dummy()
-                        ^
 COMPILATION_ERROR

compiler/testData/compileKotlinAgainstCustomBinaries/experimentalCoroutineCallFromRelease/release.kt

@@ -1,12 +1,11 @@
 suspend fun callRelease() {
-    c()
     WithTypeParameter<suspend () -> Unit>()
     returnsSuspend()
-    builder {}
     withTypeParameter<suspend () -> Unit>()
 
-    dummy()
-    C().dummy()
-    WithNested.Nested().dummy()
-    WithInner().Inner().dummy()
+    suspendFunctionNested(listOf(suspend {  }))
+    suspendFunctionNestedInFunctionType {}
+    suspendFunctionType3 { x, y, z -> }
+
+    suspendVarargs({}, {})
 }