new loplugin sequentialassign

Look for places we are assigning to the same variable twice
in succession, which means we can simplify that to a single assign

Change-Id: I499d20e28f5595e81e927bef8e1bf364eea8ba91
Reviewed-on: https://gerrit.libreoffice.org/70531
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/test/sequentialassign.cxx

+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <rtl/ustring.hxx>
+
+namespace test1
+{
+void f(OUString s1)
+{
+    OUString s2 = s1;
+    // expected-error@+1 {{simplify by merging with the preceding assignment [loplugin:sequentialassign]}}
+    s2 = s2.getToken(0, '(');
+}
+}
+
+namespace test2
+{
+OUString s2;
+void f(OUString s1)
+{
+    s2 = s1;
+    // expected-error@+1 {{simplify by merging with the preceding assignment [loplugin:sequentialassign]}}
+    s2 = s2.getToken(0, '(');
+}
+}
+
+namespace test3
+{
+struct VolumeInfo
+{
+    OUString getFileSystemName();
+};
+OUString aNullURL("");
+void f(VolumeInfo _aVolumeInfo)
+{
+    OUString aFileSysName(aNullURL);
+    // expected-error@+1 {{simplify by merging with the preceding assignment [loplugin:sequentialassign]}}
+    aFileSysName = _aVolumeInfo.getFileSystemName();
+}
+}
+
+namespace test4
+{
+struct B3DVector
+{
+    B3DVector getPerpendicular();
+};
+void f(B3DVector aNewVPN)
+{
+    B3DVector aNewToTheRight = aNewVPN;
+    // expected-error@+1 {{simplify by merging with the preceding assignment [loplugin:sequentialassign]}}
+    aNewToTheRight = aNewToTheRight.getPerpendicular();
+}
+}
+
+namespace test5
+{
+void f(OUString s, int x)
+{
+    int nPos = x;
+    // expected-error@+1 {{simplify by merging with the preceding assignment [loplugin:sequentialassign]}}
+    nPos = s.indexOf("x", nPos);
+}
+}
+
+namespace test6
+{
+void f()
+{
+    OUString s2("xxxx");
+    s2 = s2.getToken(0, '('); // no warning expected
+}
+}
+
+namespace test7
+{
+class Class1
+{
+    OUString m_field1;
+    void foo(Class1& rOther)
+    {
+        OUString s = rOther.m_field1;
+        // expected-error@+1 {{simplify by merging with the preceding assignment [loplugin:sequentialassign]}}
+        s = s.copy(1, 2);
+    }
+};
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

solenv/CompilerTest_compilerplugins_clang.mk

@@ -51,6 +51,7 @@ $(eval $(call gb_CompilerTest_add_exception_objects,compilerplugins_clang, \
     compilerplugins/clang/test/salcall \
     compilerplugins/clang/test/sallogareas \
     compilerplugins/clang/test/salunicodeliteral \
+    compilerplugins/clang/test/sequentialassign \
     compilerplugins/clang/test/shouldreturnbool \
     compilerplugins/clang/test/simplifybool \
     compilerplugins/clang/test/simplifyconstruct \