fix: param noexcept on throwing constructor

Author: alandefreitas

include/boost/url/param.hpp

@@ -356,7 +356,7 @@ struct param
     param(
         core::string_view key,
         core::string_view value,
-        bool has_value) noexcept
+        bool has_value)
         : key(key)
         , value(has_value
             ? value

test/unit/param.cpp

@@ -44,6 +44,14 @@ struct param_test
     // cheap, loses pct-validation
     BOOST_CORE_STATIC_ASSERT(std::is_constructible<param_view, param_pct_view>::value);
 
+    // param allocates std::string members
+    BOOST_CORE_STATIC_ASSERT(
+        !std::is_nothrow_constructible<
+            param,
+            core::string_view,
+            core::string_view,
+            bool>::value);
+
     // expensive constructions
     BOOST_CORE_STATIC_ASSERT(std::is_constructible<param_pct_view, param>::value);
     BOOST_CORE_STATIC_ASSERT(std::is_constructible<param_pct_view, param_view>::value);
@@ -163,6 +171,18 @@ struct param_test
             BOOST_TEST_GE(qp.value.capacity(), 100);
         }
 
+        // param(string_view, string_view, bool) - 3-arg ctor
+        {
+            {
+                param qp("key", "value", true);
+                check(qp, "key", "value", true);
+            }
+            {
+                param qp("key", "value", false);
+                check(qp, "key", "", false);
+            }
+        }
+
         // operator->
         {
             param qp("key", "value");