[groovy] prefer overload with 0 distance instead of -1, because -1 means mismatch

This fixes overload resolution for null argument.

plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/impl/distance.kt

@@ -41,10 +41,13 @@ fun compare(left: ArgumentMapping, right: ArgumentMapping): Int {
     return -1
   }
 
-  // prefer one will less distance
   val leftDistance = (left as PositionalArgumentMapping).distance
   val rightDistance = (right as PositionalArgumentMapping).distance
-  return leftDistance.compareTo(rightDistance)
+  return when {
+    leftDistance == 0L -> -1
+    rightDistance == 0L -> 1
+    else -> leftDistance.compareTo(rightDistance) // prefer one with less distance
+  }
 }
 
 fun positionalParametersDistance(map: Map<Argument, PsiParameter>, context: PsiElement): Long {

plugins/groovy/test/org/jetbrains/plugins/groovy/lang/resolve/ResolveMethodOverloadsTest.groovy

@@ -0,0 +1,42 @@
+// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package org.jetbrains.plugins.groovy.lang.resolve
+
+import com.intellij.psi.PsiMethod
+import groovy.transform.CompileStatic
+import org.jetbrains.plugins.groovy.lang.psi.api.statements.typedef.members.GrMethod
+import org.jetbrains.plugins.groovy.util.GroovyLatestTest
+import org.jetbrains.plugins.groovy.util.ResolveTest
+import org.junit.Test
+
+import static com.intellij.psi.CommonClassNames.JAVA_LANG_OBJECT
+import static com.intellij.psi.CommonClassNames.JAVA_UTIL_LIST
+
+@CompileStatic
+class ResolveMethodOverloadsTest extends GroovyLatestTest implements ResolveTest {
+
+  @Test
+  void 'void argument List vs Object'() {
+    def method = resolveTest 'def foo(Object o); def foo(List l); void bar(); <caret>foo(bar())', GrMethod
+    assert method.parameterList.parameters.first().type.equalsToText(JAVA_LANG_OBJECT)
+  }
+
+  @Test
+  void 'null argument List vs Object'() {
+    def method = resolveTest 'def foo(Object o); def foo(List l); <caret>foo(null)', GrMethod
+    assert method.parameterList.parameters.first().type.equalsToText(JAVA_LANG_OBJECT)
+  }
+
+  @Test
+  void 'list equals null'() {
+    def method = resolveTest 'void usage(List<String> l) { l.<caret>equals(null) }', PsiMethod
+    assert method.containingClass.qualifiedName == JAVA_UTIL_LIST
+    assert method.parameterList.parameters.last().type.equalsToText(JAVA_LANG_OBJECT)
+  }
+
+  @Test
+  void 'list == null'() {
+    def method = resolveTest 'void usage(List<String> l) { l <caret>== null }', PsiMethod
+    assert method.containingClass.qualifiedName == JAVA_UTIL_LIST
+    assert method.parameterList.parameters.last().type.equalsToText(JAVA_LANG_OBJECT)
+  }
+}

plugins/groovy/test/org/jetbrains/plugins/groovy/lang/resolve/ResolveMethodTest.groovy

@@ -2108,20 +2108,6 @@ class Fo {
     assertEquals('C', clazz.qualifiedName)
   }
 
-  void 'test list equals null'() {
-    def method = resolveByText '''\
-void usage(List<String> l) { l.<caret>equals(null) }
-''', GrGdkMethod
-    assert method.staticMethod.parameterList.parameters.last().type.equalsToText("java.util.List")
-  }
-
-  void 'test list == null'() {
-    def method = resolveByText '''\
-void usage(List<String> l) { l <caret>== null }
-''', GrGdkMethod
-    assert method.staticMethod.parameterList.parameters.last().type.equalsToText("java.util.List")
-  }
-
   void testSuperReferenceWithTraitQualifier() {
     def method = resolveByText('''
 trait A {

plugins/groovy/test/org/jetbrains/plugins/groovy/util/ResolveTest.java

@@ -35,18 +35,19 @@ public interface ResolveTest extends BaseTest {
     return referenceByText(text).resolve(false);
   }
 
-  default <T extends PsiElement> void resolveTest(@NotNull String text, @Nullable Class<T> clazz) {
-    resolveTest(referenceByText(text), clazz);
+  default <T extends PsiElement> T resolveTest(@NotNull String text, @Nullable Class<T> clazz) {
+    return resolveTest(referenceByText(text), clazz);
   }
 
-  default <T extends PsiElement> void resolveTest(@NotNull GroovyReference reference, @Nullable Class<T> clazz) {
+  default <T extends PsiElement> T resolveTest(@NotNull GroovyReference reference, @Nullable Class<T> clazz) {
     Collection<? extends GroovyResolveResult> results = reference.resolve(false);
     if (clazz == null) {
       assertEmpty(results);
+      return null;
     }
     else {
       PsiElement resolved = assertOneElement(results).getElement();
-      assertInstanceOf(resolved, clazz);
+      return assertInstanceOf(resolved, clazz);
     }
   }
 }