Implement ad hoc regex pattern rule support

An ad hoc pattern rule consists of a pattern that mimics a dependency
declaration followed by one or more recipes. For example:

exe{~'/(.*)/'}: cxx{~'/\1/'}
{{
  $cxx.path -o $path($>) $path($<[0])
}}

If a pattern matches a dependency declaration of a target, then the recipe is
used to perform the corresponding operation on this target. For example, the
following dependency declaration matches the above pattern which means the
rule's recipe will be used to update this target:

exe{hello}: cxx{hello}

While the following declarations do not match the above pattern:

exe{hello}:   c{hello}  # Type mismatch.
exe{hello}: cxx{howdy}  # Name mismatch.

On the left hand side of `:` in the pattern we can have a single target or an
ad hoc target group. The single target or the first (primary) ad hoc group
member must be a regex pattern (~). The rest of the ad hoc group members can
be patterns or substitutions (^). For example:

<exe{~'/(.*)/'} file{^'/\1.map/'}>: cxx{~'/\1/'}
{{
  $cxx.path -o $path($>[0]) "-Wl,-Map=$path($>[1])" $path($<[0])
}}

On the left hand side of `:` in the pattern we have prerequisites which can
be patterns, substitutions, or non-patterns. For example:

<exe{~'/(.*)/'} file{^'/\1.map/'}>: cxx{~'/\1/'} hxx{^'/\1/'} hxx{common}
{{
  $cxx.path -o $path($>[0]) "-Wl,-Map=$path($>[1])" $path($<[0])
}}

Substitutions on the left hand side of `:` and substitutions and non-patterns
on the right hand side are added to the dependency declaration. For example,
given the above rule and dependency declaration, the effective dependency is
going to be:

<exe{hello} file{hello.map>: cxx{hello} hxx{hello} hxx{common}

1 files changed, 16 insertions, 9 deletions

diff --git a/libbuild2/adhoc-rule-cxx.cxx b/libbuild2/adhoc-rule-cxx.cxx
index e061a06..5576eda 100644
--- a/libbuild2/adhoc-rule-cxx.cxx
+++ b/libbuild2/adhoc-rule-cxx.cxx
@@ -27,8 +27,10 @@ namespace build2
   // adhoc_cxx_rule
   //
   adhoc_cxx_rule::
-  adhoc_cxx_rule (const location& l, size_t b, uint64_t v, optional<string> s)
-      : adhoc_rule ("<ad hoc c++ recipe>", l, b),
+  adhoc_cxx_rule (string n, const location& l, size_t b,
+                  uint64_t v,
+                  optional<string> s)
+      : adhoc_rule (move (n), l, b),
         version (v),
         separator (move (s)),
         impl (nullptr)
@@ -38,8 +40,7 @@ namespace build2
   }
 
   bool adhoc_cxx_rule::
-  recipe_text (context&, const scope&, const target*, const adhoc_actions&,
-               string&& t, attributes&)
+  recipe_text (context&, const scope&, const target*, string&& t, attributes&)
   {
     code = move (t);
     return true;
@@ -95,6 +96,9 @@ namespace build2
   bool adhoc_cxx_rule::
   match (action a, target& t, const string& hint, match_extra& me) const
   {
+    if (pattern != nullptr && !pattern->match (a, t, hint, me))
+      return false;
+
     tracer trace ("adhoc_cxx_rule::match");
 
     context& ctx (t.ctx);
@@ -123,7 +127,8 @@ namespace build2
       if ((impl = this->impl.load (memory_order_relaxed)) != nullptr)
         break;
 
-      using create_function = cxx_rule_v1* (const location&, target_state);
+      using create_function = cxx_rule_v1* (
+        const location&, target_state, const adhoc_rule_pattern*);
       using load_function = create_function* ();
 
       // The only way to guarantee that the name of our module matches its
@@ -434,9 +439,10 @@ namespace build2
         // user-defined.
         //
         ofs << "  static cxx_rule_v1*"                                  << '\n'
-            << "  create_" << id << " (const location& l, target_state s)" << '\n'
+            << "  create_" << id << " (const location& l, target_state s, " <<
+          "const adhoc_rule_pattern* p)"                                << '\n'
             << "  {"                                                    << '\n'
-            << "    return new rule (l, s);"                            << '\n'
+            << "    return new rule (l, s, p);"                         << '\n'
             << "  }"                                                    << '\n'
             << '\n';
 
@@ -463,7 +469,8 @@ namespace build2
             << "#ifdef _WIN32"                                          << '\n'
             << "__declspec(dllexport)"                                  << '\n'
             << "#endif"                                                 << '\n'
-            << "cxx_rule_v1* (*" << sym << " ()) (const location&, target_state)" << '\n'
+            << "cxx_rule_v1* (*" << sym << " ()) (const location&, " <<
+          "target_state, const adhoc_rule_pattern*)"                    << '\n'
             << "{"                                                      << '\n'
             << "  return &rule_" << id << "::create_" << id << ";"      << '\n'
             << "}"                                                      << '\n'
@@ -652,7 +659,7 @@ namespace build2
         load_function* lf (function_cast<load_function*> (hs.second));
         create_function* cf (lf ());
 
-        impl = cf (loc, l->executed_state (perform_update_id));
+        impl = cf (loc, l->executed_state (perform_update_id), pattern);
         this->impl.store (impl, memory_order_relaxed); // Still in load phase.
       }
     }