Generic type arguments inference for lambdas as suspend functions.

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

@@ -17,10 +17,7 @@
 package org.jetbrains.kotlin.resolve
 
 import com.intellij.psi.PsiElement
-import org.jetbrains.kotlin.builtins.KotlinBuiltIns
-import org.jetbrains.kotlin.builtins.getReceiverTypeFromFunctionType
-import org.jetbrains.kotlin.builtins.getValueParameterTypesFromFunctionType
-import org.jetbrains.kotlin.builtins.isFunctionType
+import org.jetbrains.kotlin.builtins.*
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.descriptors.annotations.AnnotationsImpl
@@ -239,7 +236,7 @@ class FunctionDescriptorResolver(
         return replaceAnnotations(AnnotationsImpl(annotations.filter { it != parameterNameAnnotation }))
     }
 
-    private fun KotlinType.functionTypeExpected() = !TypeUtils.noExpectedType(this) && isFunctionType
+    private fun KotlinType.functionTypeExpected() = !TypeUtils.noExpectedType(this) && isBuiltinFunctionalType
     private fun KotlinType.getReceiverType(): KotlinType? =
             if (functionTypeExpected()) this.getReceiverTypeFromFunctionType() else null
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/CallResolverUtil.kt

@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.resolve.calls.callResolverUtil
 import com.google.common.collect.Lists
 import com.intellij.util.containers.ContainerUtil
 import org.jetbrains.kotlin.builtins.ReflectionTypes
+import org.jetbrains.kotlin.builtins.isSuspendFunctionType
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.impl.TypeAliasConstructorDescriptorImpl
 import org.jetbrains.kotlin.lexer.KtToken
@@ -50,19 +51,19 @@ enum class ResolveArgumentsMode {
 
 
 fun hasUnknownFunctionParameter(type: KotlinType): Boolean {
-    assert(ReflectionTypes.isCallableType(type)) { "type $type is not a function or property" }
+    assert(ReflectionTypes.isCallableType(type) || type.isSuspendFunctionType) { "type $type is not a function or property" }
     return getParameterArgumentsOfCallableType(type).any {
         it.type.contains { TypeUtils.isDontCarePlaceholder(it) } || ErrorUtils.containsUninferredParameter(it.type)
     }
 }
 
 fun hasUnknownReturnType(type: KotlinType): Boolean {
-    assert(ReflectionTypes.isCallableType(type)) { "type $type is not a function or property" }
+    assert(ReflectionTypes.isCallableType(type) || type.isSuspendFunctionType) { "type $type is not a function or property" }
     return ErrorUtils.containsErrorType(getReturnTypeForCallable(type))
 }
 
 fun replaceReturnTypeForCallable(type: KotlinType, given: KotlinType): KotlinType {
-    assert(ReflectionTypes.isCallableType(type)) { "type $type is not a function or property" }
+    assert(ReflectionTypes.isCallableType(type) || type.isSuspendFunctionType) { "type $type is not a function or property" }
     val newArguments = Lists.newArrayList<TypeProjection>()
     newArguments.addAll(getParameterArgumentsOfCallableType(type))
     newArguments.add(TypeProjectionImpl(Variance.INVARIANT, given))

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/GenericCandidateResolver.kt

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.resolve.calls
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.builtins.ReflectionTypes
+import org.jetbrains.kotlin.builtins.isBuiltinFunctionalTypeOrSubtype
 import org.jetbrains.kotlin.builtins.isFunctionTypeOrSubtype
 import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
@@ -308,7 +309,7 @@ class GenericCandidateResolver(private val argumentTypeResolver: ArgumentTypeRes
         if (expectedType == null || TypeUtils.isDontCarePlaceholder(expectedType)) {
             expectedType = argumentTypeResolver.getShapeTypeOfFunctionLiteral(functionLiteral, context.scope, context.trace, false)
         }
-        if (expectedType == null || !expectedType.isFunctionTypeOrSubtype || hasUnknownFunctionParameter(expectedType)) {
+        if (expectedType == null || !expectedType.isBuiltinFunctionalTypeOrSubtype || hasUnknownFunctionParameter(expectedType)) {
             return
         }
         val dataFlowInfoForArguments = context.candidateCall.dataFlowInfoForArguments

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/inference/ConstraintSystemBuilderImpl.kt

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.resolve.calls.inference
 
 import org.jetbrains.kotlin.builtins.createFunctionType
 import org.jetbrains.kotlin.builtins.isExtensionFunctionType
+import org.jetbrains.kotlin.builtins.isSuspendFunctionType
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl.ConstraintKind.EQUAL
@@ -448,5 +449,6 @@ internal fun createTypeForFunctionPlaceholder(
         functionPlaceholderTypeConstructor.argumentTypes
     }
     val receiverType = if (isExtension) DONT_CARE else null
-    return createFunctionType(functionPlaceholder.builtIns, Annotations.EMPTY, receiverType, newArgumentTypes, null, DONT_CARE)
+    return createFunctionType(functionPlaceholder.builtIns, Annotations.EMPTY, receiverType, newArgumentTypes, null, DONT_CARE,
+                              suspendFunction = expectedType.isSuspendFunctionType)
 }

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

@@ -14,4 +14,4 @@ fun test4(): suspend () -> Unit = useSuspendFn {}
 
 fun test5(sfn: suspend () -> Unit) = ambiguous(sfn)
 fun test6(fn: () -> Unit) = ambiguous(fn)
-fun test7(): () -> Unit = ambiguous {}
+fun test7(): () -> Unit = <!OVERLOAD_RESOLUTION_AMBIGUITY!>ambiguous<!> {}

compiler/testData/diagnostics/tests/coroutines/suspendFunctionType/inference1.kt

@@ -0,0 +1,7 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun <T> withS(x: T, sfn: suspend (T) -> Unit) = x
+
+val test1 = withS(100) {}
+
+fun <TT> test2(x: TT) = withS(x) {}

compiler/testData/diagnostics/tests/coroutines/suspendFunctionType/inference1.txt

@@ -0,0 +1,5 @@
+package
+
+public val test1: kotlin.Int
+public fun </*0*/ TT> test2(/*0*/ x: TT): TT
+public fun </*0*/ T> withS(/*0*/ x: T, /*1*/ sfn: suspend (T) -> kotlin.Unit): T

compiler/testData/diagnostics/tests/coroutines/suspendFunctionType/inference2.kt

@@ -0,0 +1,5 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun <T1, T2> withS2(x: T1, sfn1: suspend (T1) -> T2, sfn2: suspend (T2) -> Unit): T2 = null!!
+
+val test1 = withS2(100, { "" }, { })

compiler/testData/diagnostics/tests/coroutines/suspendFunctionType/inference2.txt

@@ -0,0 +1,4 @@
+package
+
+public val test1: kotlin.String
+public fun </*0*/ T1, /*1*/ T2> withS2(/*0*/ x: T1, /*1*/ sfn1: suspend (T1) -> T2, /*2*/ sfn2: suspend (T2) -> kotlin.Unit): T2