Add GetNamespaceByFullName and use it to speed up AssignVariableNames.CollectAllLowerCaseTypeNames

ICSharpCode.Decompiler/IL/Transforms/AssignVariableNames.cs

@@ -165,11 +165,9 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 
 		static IEnumerable<string> CollectAllLowerCaseTypeNames(ITypeDefinition type)
 		{
-
-			foreach (var item in type.ParentModule.TopLevelTypeDefinitions)
+			var ns = type.ParentModule.Compilation.GetNamespaceByFullName(type.Namespace);
+			foreach (var item in ns.Types)
 			{
-				if (item.Namespace != type.Namespace)
-					continue;
 				if (IsLowerCase(item.Name))
 					yield return item.Name;
 			}

ICSharpCode.Decompiler/TypeSystem/TypeSystemExtensions.cs

@@ -748,5 +748,21 @@ namespace ICSharpCode.Decompiler.TypeSystem
 				return new ParameterizedType(td, td.TypeArguments);
 			}
 		}
+
+		public static INamespace GetNamespaceByFullName(this ICompilation compilation, string name)
+		{
+			if (string.IsNullOrEmpty(name))
+				return compilation.RootNamespace;
+			var parts = name.Split('.');
+			var ns = compilation.RootNamespace;
+			foreach (var part in parts)
+			{
+				var child = ns.GetChildNamespace(part);
+				if (child == null)
+					return null;
+				ns = child;
+			}
+			return ns;
+		}
 	}
 }