Introduce 'SuspendFunction$n<...>' types.

compiler/frontend/src/org/jetbrains/kotlin/resolve/TypeResolver.kt

@@ -134,7 +134,7 @@ class TypeResolver(
 
         val typeElement = typeReference.typeElement
 
-        val type = resolveTypeElement(c, annotations, typeElement)
+        val type = resolveTypeElement(c, annotations, typeReference.modifierList, typeElement)
         c.trace.recordScope(c.scope, typeReference)
 
         if (!type.isBare) {
@@ -175,8 +175,14 @@ class TypeResolver(
         }
     }
 
-    private fun resolveTypeElement(c: TypeResolutionContext, annotations: Annotations, typeElement: KtTypeElement?): PossiblyBareType {
+    private fun resolveTypeElement(c: TypeResolutionContext, annotations: Annotations, modifiers: KtModifierList?, typeElement: KtTypeElement?): PossiblyBareType {
         var result: PossiblyBareType? = null
+
+        val hasSuspendModifier = modifiers?.hasModifier(KtTokens.SUSPEND_KEYWORD) ?: false
+        if (hasSuspendModifier && typeElement !is KtFunctionType) {
+            c.trace.report(Errors.WRONG_MODIFIER_TARGET.on(modifiers!!.getModifier(KtTokens.SUSPEND_KEYWORD)!!, KtTokens.SUSPEND_KEYWORD, "non-functional type"))
+        }
+
         typeElement?.accept(object : KtVisitorVoid() {
             override fun visitUserType(type: KtUserType) {
                 val qualifierResolutionResult = resolveDescriptorForType(c.scope, type, c.trace, c.isDebuggerContext)
@@ -198,7 +204,7 @@ class TypeResolver(
 
             override fun visitNullableType(nullableType: KtNullableType) {
                 val innerType = nullableType.getInnerType()
-                val baseType = resolveTypeElement(c, annotations, innerType)
+                val baseType = resolveTypeElement(c, annotations, modifiers, innerType)
                 if (baseType.isNullable || innerType is KtNullableType || innerType is KtDynamicType) {
                     c.trace.report(REDUNDANT_NULLABLE.on(nullableType))
                 }
@@ -219,7 +225,8 @@ class TypeResolver(
                         moduleDescriptor.builtIns, annotations, receiverType,
                         parameterDescriptors.map { it.type },
                         parameterDescriptors.map { it.name },
-                        returnType
+                        returnType,
+                        suspendFunction = hasSuspendModifier
                 ))
             }
 

compiler/testData/diagnostics/tests/coroutines/suspendFunctionType/modifierApplicability.kt

@@ -0,0 +1,14 @@
+typealias Action = () -> Unit
+
+interface SAM {
+    fun run()
+}
+
+typealias Test1 = suspend () -> Unit
+typealias Test2 = suspend Int.(String) -> Unit
+typealias Test3 = <!WRONG_MODIFIER_TARGET!>suspend<!> Function0<Unit>
+typealias Test4 = <!WRONG_MODIFIER_TARGET!>suspend<!> Action
+typealias Test5 = List<suspend () -> Unit>
+typealias Test6 = <!WRONG_MODIFIER_TARGET!>suspend<!> List<() -> Unit>
+typealias Test7 = <!WRONG_MODIFIER_TARGET!>suspend<!> SAM
+typealias Test8 = SuspendFunction0<Unit>

compiler/testData/diagnostics/tests/coroutines/suspendFunctionType/modifierApplicability.txt

@@ -0,0 +1,17 @@
+package
+
+public interface SAM {
+    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 abstract fun run(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+public typealias Action = () -> kotlin.Unit
+public typealias Test1 = suspend () -> kotlin.Unit
+public typealias Test2 = suspend kotlin.Int.(kotlin.String) -> kotlin.Unit
+public typealias Test3 = () -> kotlin.Unit
+public typealias Test4 = Action
+public typealias Test5 = kotlin.collections.List<suspend () -> kotlin.Unit>
+public typealias Test6 = kotlin.collections.List<() -> kotlin.Unit>
+public typealias Test7 = SAM
+public typealias Test8 = suspend () -> kotlin.Unit