Fix KT-10472: compare all overloads including varargs in a single pass.

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/results/OverloadingConflictResolver.kt

@@ -88,17 +88,9 @@ class OverloadingConflictResolver(private val builtIns: KotlinBuiltIns) {
             CandidateCallWithArgumentMapping.create(candidateCall) { it.arguments.filter { it.getArgumentExpression() != null } }
         }
 
-        val (varargCandidates, regularCandidates) = conflictingCandidates.partition { it.resultingDescriptor.hasVarargs }
-        val mostSpecificRegularCandidates = regularCandidates.selectMostSpecificCallsWithArgumentMapping(discriminateGenericDescriptors)
+        val mostSpecificCandidates = conflictingCandidates.selectMostSpecificCallsWithArgumentMapping(discriminateGenericDescriptors)
 
-        return when {
-            mostSpecificRegularCandidates.size > 1 ->
-                null
-            mostSpecificRegularCandidates.size == 1 ->
-                mostSpecificRegularCandidates.single()
-            else ->
-                varargCandidates.selectMostSpecificCallsWithArgumentMapping(discriminateGenericDescriptors).singleOrNull()
-        }
+        return mostSpecificCandidates.singleOrNull()
     }
 
     private fun <D : CallableDescriptor, K> Collection<CandidateCallWithArgumentMapping<D, K>>.selectMostSpecificCallsWithArgumentMapping(
@@ -139,7 +131,7 @@ class OverloadingConflictResolver(private val builtIns: KotlinBuiltIns) {
 
     /**
      * Returns `true` if `d1` is definitely not less specific than `d2`,
-     * `false` if `d1` is definitely less specific than `d2` or undecided.
+     * `false` otherwise.
      */
     private fun <D : CallableDescriptor, K> compareCallsWithArgumentMapping(
             call1: CandidateCallWithArgumentMapping<D, K>,
@@ -160,6 +152,11 @@ class OverloadingConflictResolver(private val builtIns: KotlinBuiltIns) {
             return it
         }
 
+        val hasVarargs1 = call1.resultingDescriptor.hasVarargs
+        val hasVarargs2 = call2.resultingDescriptor.hasVarargs
+        if (hasVarargs1 && !hasVarargs2) return false
+        if (!hasVarargs1 && hasVarargs2) return true
+
         assert(call1.argumentsCount == call2.argumentsCount) {
             "$call1 and $call2 have different number of explicit arguments"
         }

compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt10472.kt

@@ -0,0 +1,13 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+object Right
+object Wrong
+
+interface A<T>
+interface B<T> : A<T>
+
+fun <T> foo(vararg t: T) = Wrong
+fun <T> foo(t: A<T>) = Wrong
+fun <T> foo(t: B<T>) = Right
+
+fun test(b: B<Int>): Right = foo(b)

compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt10472.txt

@@ -0,0 +1,32 @@
+package
+
+public fun </*0*/ T> foo(/*0*/ t: A<T>): Wrong
+public fun </*0*/ T> foo(/*0*/ t: B<T>): Right
+public fun </*0*/ T> foo(/*0*/ vararg t: T /*kotlin.Array<out T>*/): Wrong
+public fun test(/*0*/ b: B<kotlin.Int>): Right
+
+public interface A</*0*/ T> {
+    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 open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface B</*0*/ T> : A<T> {
+    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 open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public object Right {
+    private constructor Right()
+    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 open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public object Wrong {
+    private constructor Wrong()
+    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 open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

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

@@ -13742,6 +13742,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("kt10472.kt")
+                public void testKt10472() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/resolve/overloadConflicts/kt10472.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("numberOfDefaults.kt")
                 public void testNumberOfDefaults() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/resolve/overloadConflicts/numberOfDefaults.kt");