Type aliases: do not reparse RHS of type alias declaration in expanded type resolution

compiler/frontend/src/org/jetbrains/kotlin/resolve/DescriptorResolver.java

@@ -735,9 +735,7 @@ public class DescriptorResolver {
                 DeferredType.create(storageManager, trace, new Function0<KotlinType>() {
                     @Override
                     public KotlinType invoke() {
-                        // TODO do not reparse type alias RHS, just expand it instead
-                        // NB this messes up with diagnostics
-                        return typeResolver.resolveType(scopeWithTypeParameters, typeReference, trace, true);
+                        return typeResolver.resolveExpandedTypeForTypeAlias(typeAliasDescriptor);
                     }
                 }));
 

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

@@ -71,6 +71,13 @@ class TypeResolver(
         return resolveType(TypeResolutionContext(scope, trace, checkBounds, false, typeReference.suppressDiagnosticsInDebugMode(), true), typeReference)
     }
 
+    fun resolveExpandedTypeForTypeAlias(typeAliasDescriptor: TypeAliasDescriptor): KotlinType {
+        val typeAliasExpansion = createTypeAliasExpansion(null, typeAliasDescriptor, emptyList())
+        val expandedType = expandTypeAlias(typeAliasExpansion, TypeAliasExpansionReportStrategy.DEFAULT, Annotations.EMPTY, 0,
+                                           withAbbreviatedType = false)
+        return expandedType
+    }
+
     private fun resolveType(c: TypeResolutionContext, typeReference: KtTypeReference): KotlinType {
         assert(!c.allowBareTypes) { "Use resolvePossiblyBareType() when bare types are allowed" }
         return resolvePossiblyBareType(c, typeReference).getActualType()
@@ -550,7 +557,8 @@ class TypeResolver(
             typeAliasExpansion: TypeAliasExpansion,
             reportStrategy: TypeAliasExpansionReportStrategy,
             annotations: Annotations,
-            recursionDepth: Int
+            recursionDepth: Int,
+            withAbbreviatedType: Boolean = true
     ): KotlinType {
         val originalProjection = TypeProjectionImpl(Variance.INVARIANT, typeAliasExpansion.descriptor.underlyingType)
         val expandedProjection = expandTypeProjectionForTypeAlias(originalProjection, typeAliasExpansion, null, reportStrategy, recursionDepth)
@@ -562,13 +570,18 @@ class TypeResolver(
             "Type alias expansion: result for ${typeAliasExpansion.descriptor} is ${expandedProjection.projectionKind}, should be invariant"
         }
 
-        val abbreviatedType = KotlinTypeImpl.create(annotations,
-                                                    typeAliasExpansion.descriptor.typeConstructor,
-                                                    originalProjection.type.isMarkedNullable,
-                                                    typeAliasExpansion.arguments,
-                                                    MemberScope.Empty)
+        return if (withAbbreviatedType) {
+            val abbreviatedType = KotlinTypeImpl.create(annotations,
+                                                        typeAliasExpansion.descriptor.typeConstructor,
+                                                        originalProjection.type.isMarkedNullable,
+                                                        typeAliasExpansion.arguments,
+                                                        MemberScope.Empty)
 
-        return expandedType.withAbbreviatedType(abbreviatedType)
+            expandedType.withAbbreviatedType(abbreviatedType)
+        }
+        else {
+            expandedType
+        }
     }
 
     private fun expandTypeProjectionForTypeAlias(

compiler/testData/codegen/box/typealias/simple.kt

@@ -1,5 +1,7 @@
 typealias S = String
 
-val OK: S = "OK"
+typealias SF<T> = (T) -> S
 
-fun box(): S = OK
+val f: SF<S> = { it }
+
+fun box(): S = f("OK")

compiler/testData/diagnostics/tests/typealias/boundsViolationInTypeAliasRHS.kt

@@ -2,8 +2,8 @@
 
 class TColl<T, C : Collection<T>>
 
-typealias TCErr = TColl<String, <!UPPER_BOUND_VIOLATED, UPPER_BOUND_VIOLATED!>Any<!>>
-typealias TCErr2 = <!UPPER_BOUND_VIOLATED_IN_TYPEALIAS_EXPANSION!>TCErr<!>
+typealias TCErr = TColl<String, <!UPPER_BOUND_VIOLATED!>Any<!>>
+typealias TCErr2 = TCErr
 
 fun testType1(x: <!UPPER_BOUND_VIOLATED_IN_TYPEALIAS_EXPANSION!>TCErr<!>) {}
 val testCtor1 = <!UPPER_BOUND_VIOLATED_IN_TYPEALIAS_EXPANSION!>TCErr()<!>

compiler/testData/diagnostics/tests/typealias/functionTypeInTypeAlias.kt

@@ -0,0 +1,3 @@
+val f: () -> Unit = {}
+
+typealias F = () -> Unit

compiler/testData/diagnostics/tests/typealias/functionTypeInTypeAlias.txt

@@ -0,0 +1,4 @@
+package
+
+public typealias F = () -> kotlin.Unit
+public val f: () -> kotlin.Unit

compiler/testData/diagnostics/tests/typealias/recursive.kt

@@ -1,4 +1,4 @@
-typealias A = <!RECURSIVE_TYPEALIAS_EXPANSION!>B<!>
-typealias B = <!RECURSIVE_TYPEALIAS_EXPANSION!>A<!>
+typealias A = B
+typealias B = A
 
 val x: <!RECURSIVE_TYPEALIAS_EXPANSION!>A<!> = TODO()

compiler/testData/diagnostics/tests/typealias/substitutionVariance.kt

@@ -3,13 +3,13 @@ class Out<out T>
 class Inv<T>
 
 typealias In1<T> = In<T>
-typealias In2<T> = In<<!REDUNDANT_PROJECTION, REDUNDANT_PROJECTION!>in<!> T>
-typealias In3<T> = In<<!CONFLICTING_PROJECTION, CONFLICTING_PROJECTION!>out<!> T>
+typealias In2<T> = In<<!REDUNDANT_PROJECTION!>in<!> T>
+typealias In3<T> = In<<!CONFLICTING_PROJECTION!>out<!> T>
 typealias In4<T> = In<*>
 
 typealias Out1<T> = Out<T>
-typealias Out2<T> = Out<<!CONFLICTING_PROJECTION, CONFLICTING_PROJECTION!>in<!> T>
-typealias Out3<T> = Out<<!REDUNDANT_PROJECTION, REDUNDANT_PROJECTION!>out<!> T>
+typealias Out2<T> = Out<<!CONFLICTING_PROJECTION!>in<!> T>
+typealias Out3<T> = Out<<!REDUNDANT_PROJECTION!>out<!> T>
 typealias Out4<T> = Out<*>
 
 typealias Inv1<T> = Inv<T>

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

@@ -19296,6 +19296,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("functionTypeInTypeAlias.kt")
+            public void testFunctionTypeInTypeAlias() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/typealias/functionTypeInTypeAlias.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("genericTypeAliasConstructor.kt")
             public void testGenericTypeAliasConstructor() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/typealias/genericTypeAliasConstructor.kt");

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/AbstractTypeAliasDescriptor.kt

@@ -88,6 +88,8 @@ abstract class AbstractTypeAliasDescriptor(
 
         override val annotations: Annotations
             get() = declarationDescriptor.annotations
+
+        override fun toString(): String = "[typealias ${declarationDescriptor.name.asString()}]"
     }
 
 }