diff --git a/.appveyor.yml b/.appveyor.yml
index bd69995445..ef3f4e4075 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -56,7 +56,6 @@ before_build:
           -wd4996  # Call to 'std::copy' with parameters that may be unsafe
           -wd4100  # unreferenced formal parameter
           -wd4310  # cast truncates constant value
-          -wd4457  # declaration of 'varname' hides function parameter
           -wd4458  # declaration of 'varname' hides class member
           -wd4459  # declaration of 'varname' hides global declaration
           -wd4512  # assignment operator could not be generated
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f96da6b8a2..c2d4cdf8ad 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -413,6 +413,11 @@ jobs:
           variant sanitize : <optimization>speed <debug-symbols>off <inlining>full
                              <runtime-debugging>off ;
 
+          # Enable additional warnings
+          toolset.flags gcc.compile OPTIONS <warnings>extra :
+              -Wshadow-local
+            : unchecked ;
+
           # Ignore some warnings
           feature.feature known-warnings : suppress : optional incidental propagated ;
           toolset.flags gcc.compile OPTIONS <known-warnings>suppress :
diff --git a/.travis.yml b/.travis.yml
index c95a0df789..af65877393 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -107,6 +107,11 @@ before_install:
     variant sanitize : <optimization>speed <debug-symbols>off <inlining>full
                        <runtime-debugging>off ;
 
+    # Enable additional warnings
+    toolset.flags gcc.compile OPTIONS <warnings>extra :
+        -Wshadow-local
+      : unchecked ;
+
     # Ignore some warnings
     feature.feature known-warnings : suppress : optional incidental propagated ;
     toolset.flags gcc.compile OPTIONS <known-warnings>suppress :
diff --git a/include/boost/spirit/home/support/detail/lexer/parser/tokeniser/re_tokeniser_helper.hpp b/include/boost/spirit/home/support/detail/lexer/parser/tokeniser/re_tokeniser_helper.hpp
index caa19ba4cb..1d4840da59 100644
--- a/include/boost/spirit/home/support/detail/lexer/parser/tokeniser/re_tokeniser_helper.hpp
+++ b/include/boost/spirit/home/support/detail/lexer/parser/tokeniser/re_tokeniser_helper.hpp
@@ -523,21 +523,21 @@ class basic_re_tokeniser_helper
 
         for (; start_ <= end_; ++start_)
         {
-            CharT ch_ = static_cast<CharT> (start_);
+            CharT ch_i = static_cast<CharT> (start_);
 
             if ((state_._flags & icase) &&
-                (std::isupper (ch_, state_._locale) ||
-                std::islower (ch_, state_._locale)))
+                (std::isupper (ch_i, state_._locale) ||
+                std::islower (ch_i, state_._locale)))
             {
-                CharT upper_ = std::toupper (ch_, state_._locale);
-                CharT lower_ = std::tolower (ch_, state_._locale);
+                CharT upper_ = std::toupper (ch_i, state_._locale);
+                CharT lower_ = std::tolower (ch_i, state_._locale);
 
                 chars_ += (upper_);
                 chars_ += (lower_);
             }
             else
             {
-                chars_ += (ch_);
+                chars_ += (ch_i);
             }
         }
     }
diff --git a/test/x3/debug.cpp b/test/x3/debug.cpp
index 5d3508ac8c..20c9bb07ee 100644
--- a/test/x3/debug.cpp
+++ b/test/x3/debug.cpp
@@ -68,9 +68,9 @@ main()
 
     { // basic tests
 
-        auto a = rule<class a>("a") = 'a';
-        auto b = rule<class b>("b") = 'b';
-        auto c = rule<class c>("c") = 'c';
+        auto a = rule<class a_id>("a") = 'a';
+        auto b = rule<class b_id>("b") = 'b';
+        auto c = rule<class c_id>("c") = 'c';
 
         {
             auto start = *(a | b | c);
@@ -89,9 +89,9 @@ main()
 
     { // basic tests w/ skipper
 
-        auto a = rule<class a>("a") = 'a';
-        auto b = rule<class b>("b") = 'b';
-        auto c = rule<class c>("c") = 'c';
+        auto a = rule<class a_id>("a") = 'a';
+        auto b = rule<class b_id>("b") = 'b';
+        auto c = rule<class c_id>("c") = 'c';
 
         {
             auto start = *(a | b | c);
@@ -133,7 +133,7 @@ main()
     {
         symbols<my_attribute> a{{{ "a", my_attribute{} }}};
 
-        auto b = rule<struct b, my_attribute>("b") = a;
+        auto b = rule<struct b_id, my_attribute>("b") = a;
 
         my_attribute attr;
 
diff --git a/test/x3/rule1.cpp b/test/x3/rule1.cpp
index c88514c2fb..71fe15fe01 100644
--- a/test/x3/rule1.cpp
+++ b/test/x3/rule1.cpp
@@ -92,17 +92,17 @@ main()
 
     { // basic tests w/ skipper but no final post-skip
 
-        auto a = rule<class a>()
+        auto a = rule<class a_id>()
             = lit('a');
 
-        auto b = rule<class b>()
+        auto b = rule<class b_id>()
             = lit('b');
 
-        auto c = rule<class c>()
+        auto c = rule<class c_id>()
             = lit('c');
 
         {
-            auto start = rule<class start>() = *(a | b) >> c;
+            auto start = rule<class start_id>() = *(a | b) >> c;
 
             char const *s1 = " a b a a b b a c ... "
               , *const e1 = s1 + std::strlen(s1);
diff --git a/test/x3/rule2.cpp b/test/x3/rule2.cpp
index 158360b850..5c308deb06 100644
--- a/test/x3/rule2.cpp
+++ b/test/x3/rule2.cpp
@@ -47,7 +47,7 @@ main()
     { // context tests
 
         char ch;
-        auto a = rule<class a, char>() = alpha;
+        auto a = rule<class a_id, char>() = alpha;
 
         // this semantic action requires the context
         auto f = [&](auto& ctx){ ch = _attr(ctx); };
@@ -71,7 +71,7 @@ main()
     { // auto rules tests
 
         char ch = '\0';
-        auto a = rule<class a, char>() = alpha;
+        auto a = rule<class a_id, char>() = alpha;
         auto f = [&](auto& ctx){ ch = _attr(ctx); };
 
         BOOST_TEST(test("x", a[f]));
@@ -98,7 +98,7 @@ main()
         auto f = [&](auto& ctx){ s = _attr(ctx); };
 
         {
-            auto r = rule<class r, std::string>()
+            auto r = rule<class r_id, std::string>()
                 = char_ >> *(',' >> char_)
                 ;
 
@@ -107,7 +107,7 @@ main()
         }
 
         {
-            auto r = rule<class r, std::string>()
+            auto r = rule<class r_id, std::string>()
                 = char_ >> *(',' >> char_);
             s.clear();
             BOOST_TEST(test("a,b,c,d,e,f", r[f]));
@@ -115,7 +115,7 @@ main()
         }
 
         {
-            auto r = rule<class r, std::string>()
+            auto r = rule<class r_id, std::string>()
                 = char_ >> char_ >> char_ >> char_ >> char_ >> char_;
             s.clear();
             BOOST_TEST(test("abcdef", r[f]));
diff --git a/test/x3/rule3.cpp b/test/x3/rule3.cpp
index e87fc5e0a9..7deeb9b788 100644
--- a/test/x3/rule3.cpp
+++ b/test/x3/rule3.cpp
@@ -138,7 +138,7 @@ int main()
     }
 
     {
-        auto r = rule<class r, int>{} = eps[([] (auto& ctx) {
+        auto r = rule<class r_id, int>{} = eps[([] (auto& ctx) {
             using boost::spirit::x3::_val;
             static_assert(std::is_same<std::decay_t<decltype(_val(ctx))>, unused_type>::value,
                 "Attribute must not be synthesized");
diff --git a/test/x3/rule4.cpp b/test/x3/rule4.cpp
index 80e2a78a0d..551be7059b 100644
--- a/test/x3/rule4.cpp
+++ b/test/x3/rule4.cpp
@@ -95,7 +95,7 @@ main()
 
         // test deduced auto rule behavior
 
-        auto text = rule<class text, std::string>()
+        auto text = rule<class text_id, std::string>()
             = +(!char_(')') >> !char_('>') >> char_);
 
         attr.clear();
@@ -119,14 +119,14 @@ main()
 
     {
         typedef boost::variant<double, int> v_type;
-        auto r1 = rule<class r1, v_type>()
+        auto r1 = rule<class r1_id, v_type>()
             = int_;
         v_type v;
         BOOST_TEST(test_attr("1", r1, v) && v.which() == 1 &&
             boost::get<int>(v) == 1);
 
         typedef boost::optional<int> ov_type;
-        auto r2 = rule<class r2, ov_type>()
+        auto r2 = rule<class r2_id, ov_type>()
             = int_;
         ov_type ov;
         BOOST_TEST(test_attr("1", r2, ov) && ov && boost::get<int>(ov) == 1);
@@ -136,7 +136,7 @@ main()
     {
         using boost::fusion::vector;
         using boost::fusion::at_c;
-        auto r = rule<class r, vector<int>>()
+        auto r = rule<class r_id, vector<int>>()
             = int_;
 
         vector<int> v(0);
diff --git a/test/x3/sequence.cpp b/test/x3/sequence.cpp
index 0839521b75..63167912bd 100644
--- a/test/x3/sequence.cpp
+++ b/test/x3/sequence.cpp
@@ -149,7 +149,7 @@ main()
         typedef deque<char, int> attr_type;
         attr_type fv;
 
-        auto r = rule<class r, attr_type>()
+        auto r = rule<class r_id, attr_type>()
             = char_ >> ',' >> int_;
 
         BOOST_TEST((test_attr("test:x,1", "test:" >> r, fv) &&
@@ -164,7 +164,7 @@ main()
         typedef deque<int> attr_type;
         attr_type fv;
 
-        auto r = rule<class r, attr_type>()
+        auto r = rule<class r_id, attr_type>()
             = int_;
 
         BOOST_TEST((test_attr("test:1", "test:" >> r, fv) &&
@@ -319,10 +319,10 @@ main()
     {
         std::vector<std::string> v;
 
-        auto e = rule<class e, std::string>()
+        auto e = rule<class e_id, std::string>()
             = *~char_(',');
 
-        auto l = rule<class l, std::vector<std::string>>()
+        auto l = rule<class l_id, std::vector<std::string>>()
             = e >> *(',' >> e);
 
         BOOST_TEST(test_attr("abc1,abc2,abc3", l, v));
@@ -342,10 +342,10 @@ main()
 
     {
         std::string s;
-        auto e = rule<class e, std::string>()
+        auto e = rule<class e_id, std::string>()
             = *~char_(',');
 
-        auto l = rule<class l, std::string>()
+        auto l = rule<class l_id, std::string>()
             = e >> *(',' >> e);
 
         BOOST_TEST(test_attr("abc1,abc2,abc3", l, s));
@@ -428,8 +428,8 @@ main()
     {
         using Attr = boost::variant<int, float>;
         Attr attr;
-        auto const term = rule<class term, Attr>("term") = int_ | float_;
-        auto const expr = rule<class expr, Attr>("expr") = term | ('(' > term > ')');
+        auto const term = rule<class term_id, Attr>("term") = int_ | float_;
+        auto const expr = rule<class expr_id, Attr>("expr") = term | ('(' > term > ')');
         BOOST_TEST((test_attr("(1)", expr, attr, space)));
     }