Fix fetching members from bases (#1742)

* Remove stale reference

* Fix fetching ctor from bases

* Test fix

(cherry picked from commit c4a5c9c)

Author: Mikhail Arkhipov

src/Analysis/Ast/Impl/Types/PythonClassType.cs

@@ -79,10 +79,8 @@ public override IEnumerable<string> GetMemberNames() {
         }
 
         public override IMember GetMember(string name) {
-            IMember member;
-
             lock (_membersLock) {
-                if (Members.TryGetValue(name, out member)) {
+                if (Members.TryGetValue(name, out var member)) {
                     return member;
                 }
             }
@@ -101,12 +99,7 @@ public override IMember GetMember(string name) {
 
             using (_memberGuard.Push(this, out var reentered)) {
                 if (!reentered) {
-                    foreach (var m in Mro.Reverse()) {
-                        if (m == this) {
-                            return member;
-                        }
-                        member = member ?? m.GetMember(name);
-                    }
+                    return Mro.Skip(1).Select(c => c.GetMember(name)).ExcludeDefault().FirstOrDefault();
                 }
                 return null;
             }

src/Analysis/Ast/Test/ClassesTests.cs

@@ -270,6 +270,23 @@ def __init__(self, value):
                 .Which.Should().HaveParameterAt(0).Which.Should().HaveName("self").And.HaveType("X");
         }
 
+        [TestMethod, Priority(0)]
+        public async Task ClassBaseInit() {
+            const string code = @"
+class A:
+    def __init__(self, value):
+        self.value = value
+
+class B(A): ...
+";
+            var analysis = await GetAnalysisAsync(code);
+            analysis.Should().HaveClass("B")
+                .Which.Should().HaveMethod("__init__")
+                .Which.Should().HaveSingleOverload()
+                .Which.Should().HaveParameterAt(1)
+                .Which.Name.Should().Be("value");
+        }
+
         [TestMethod, Priority(0)]
         public async Task ClassBase2X() {
             const string code = @"

src/LanguageServer/Impl/Sources/MarkdownDocumentationSource.cs

@@ -13,6 +13,7 @@
 // See the Apache Version 2.0 License for specific language governing
 // permissions and limitations under the License.
 
+using System.Linq;
 using Microsoft.Python.Analysis;
 using Microsoft.Python.Analysis.Types;
 using Microsoft.Python.Analysis.Values;
@@ -56,7 +57,7 @@ public MarkupContent GetHover(string name, IMember member, IPythonType self, boo
 
                     if (includeClassInit) {
                         className = cls.Name;
-                        var init = cls.GetMember<IPythonFunctionType>("__init__");
+                        var init = cls.TryGetFunctionType();
                         if (init != null) {
                             sig = GetSignatureString(init, null, out var _, 0, "", true);
                         }