Add documentation to NamespaceOrTypeSymbol.GetMembers(name) to make explicit

the ordering guarantees (deterministic, and for same kind they appear in input order).

src/Compilers/VisualBasic/Portable/Symbols/NamespaceOrTypeSymbol.vb

@@ -71,7 +71,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
         ''' Get all the members of this symbol that have a particular name.
         ''' </summary>
         ''' <returns>An ImmutableArray containing all the members of this symbol with the given name. If there are
-        ''' no members with this name, returns an empty ImmutableArray. Never returns Nothing.</returns>
+        ''' no members with this name, returns an empty ImmutableArray. The result is deteministic (i.e. the same
+        ''' from call to call and from compilation to compilation). Members of the same kind appear in the result
+        ''' in the same order in which they appeared at their origin (metadata or source).
+        ''' Never returns Nothing.</returns>
         Public MustOverride Function GetMembers(name As String) As ImmutableArray(Of Symbol)
 
         ''' <summary>

src/Compilers/VisualBasic/Test/Semantic/Binding/LookupTests.vb

@@ -2932,7 +2932,7 @@ Red,
 Green,
 DateTime,
 [System.Obsolete] Datetime = DateTime,
-DATETIME,
+[System.Obsolete] DATETIME,
 Blue,
 }
 ]]>,
@@ -3029,8 +3029,8 @@ End Module]]>,
             CompilationUtils.AssertTheseDiagnostics(vbCompilation,
                                                     <expected><![CDATA[
                                                     ]]></expected>)
+            CompileAndVerify(vbCompilation, expectedOutput:="2")
         End Sub
 
     End Class
 End Namespace
-