Prohibit callable references to suspend functions

#KT-15662 Fixed

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/DoubleColonExpressionResolver.kt

@@ -50,6 +50,7 @@ import org.jetbrains.kotlin.resolve.source.toSourceElement
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.TypeUtils.NO_EXPECTED_TYPE
 import org.jetbrains.kotlin.types.expressions.typeInfoFactory.createTypeInfo
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 import java.lang.UnsupportedOperationException
 import java.util.*
 import javax.inject.Inject
@@ -574,9 +575,22 @@ class DoubleColonExpressionResolver(
         val resolutionResults =
                 resolveCallableReferenceRHS(expression, lhsResult, context, resolveArgumentsMode)
 
+        reportUnsupportedReferenceToSuspendFunction(resolutionResults, expression, context)
+
         return lhsResult to resolutionResults
     }
 
+    private fun reportUnsupportedReferenceToSuspendFunction(
+            resolutionResults: OverloadResolutionResults<CallableDescriptor>?,
+            expression: KtCallableReferenceExpression,
+            context: ExpressionTypingContext
+    ) {
+        if (resolutionResults?.isSingleResult == true &&
+                resolutionResults.resultingDescriptor.safeAs<FunctionDescriptor>()?.isSuspend == true) {
+            context.trace.report(UNSUPPORTED.on(expression.callableReference, "Callable references to suspend functions"))
+        }
+    }
+
     private fun tryResolveRHSWithReceiver(
             traceTitle: String,
             receiver: Receiver?,

compiler/testData/diagnostics/tests/coroutines/callableReferences.kt

@@ -0,0 +1,28 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+suspend fun foo() {}
+
+class A {
+    suspend fun member() {}
+}
+
+suspend fun A.ext() {}
+
+fun test1(a: A) {
+    val x = ::<!ILLEGAL_SUSPEND_FUNCTION_CALL, UNSUPPORTED!>foo<!>
+
+    val y1 = a::<!ILLEGAL_SUSPEND_FUNCTION_CALL, UNSUPPORTED!>member<!>
+    val y2 = A::<!ILLEGAL_SUSPEND_FUNCTION_CALL, UNSUPPORTED!>member<!>
+
+    val z1 = a::<!ILLEGAL_SUSPEND_FUNCTION_CALL, UNSUPPORTED!>ext<!>
+    val z2 = A::<!ILLEGAL_SUSPEND_FUNCTION_CALL, UNSUPPORTED!>ext<!>
+}
+
+suspend fun test2(a: A) {
+    val x = ::<!UNSUPPORTED!>foo<!>
+
+    val y1 = a::<!UNSUPPORTED!>member<!>
+    val y2 = A::<!UNSUPPORTED!>member<!>
+
+    val z1 = a::<!UNSUPPORTED!>ext<!>
+    val z2 = A::<!UNSUPPORTED!>ext<!>
+}

compiler/testData/diagnostics/tests/coroutines/callableReferences.txt

@@ -0,0 +1,14 @@
+package
+
+public suspend fun foo(): kotlin.Unit
+public fun test1(/*0*/ a: A): kotlin.Unit
+public suspend fun test2(/*0*/ a: A): kotlin.Unit
+public suspend fun A.ext(): kotlin.Unit
+
+public final class A {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final suspend fun member(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -4282,6 +4282,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/tests/coroutines"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.ANY, true);
             }
 
+            @TestMetadata("callableReferences.kt")
+            public void testCallableReferences() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/coroutines/callableReferences.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("coroutinesDisabled.kt")
             public void testCoroutinesDisabled() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/coroutines/coroutinesDisabled.kt");