From 934f2a9a90c5cad3cdc8a66b50c17827a3ddbcee Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Sat, 20 Jan 2018 13:46:11 +0200
Subject: Get rid of action rule override semantics

Instead we now have two more or less separate match states for outer and
inner parts of an action.
---
 build2/rule.hxx | 44 ++++++--------------------------------------
 1 file changed, 6 insertions(+), 38 deletions(-)

(limited to 'build2/rule.hxx')

diff --git a/build2/rule.hxx b/build2/rule.hxx
index f6e23f6..8e43ca6 100644
--- a/build2/rule.hxx
+++ b/build2/rule.hxx
@@ -13,48 +13,16 @@
 
 namespace build2
 {
-  class match_result
-  {
-  public:
-    bool result;
-
-    // If set, then this is a recipe's action. It must override the original
-    // action. Normally it is "unconditional inner operation". Only
-    // noop_recipe can be overridden.
-    //
-    // It is passed to rule::apply() so that prerequisites are matched for
-    // this action. It is also passed to target::recipe() so that if someone
-    // is matching this target for this action, we won't end-up re-matching
-    // it. However, the recipe itself is executed with the original action
-    // so that it can adjust its logic, if necessary.
-    //
-    action recipe_action = action ();
-
-    explicit
-    operator bool () const {return result;}
-
-    // Note that the from-bool constructor is intentionally implicit so that
-    // we can return true/false from match().
-    //
-    match_result (bool r): result (r) {}
-    match_result (bool r, action a): result (r), recipe_action (a) {}
-  };
-
   // Once a rule is registered (for a scope), it is treated as immutable. If
   // you need to modify some state (e.g., counters or some such), then make
   // sure it is MT-safe.
   //
-  // Note that match() may not be followed by apply() or be called several
-  // times before the following apply() (see resolve_group_members()) which
-  // means that it should be idempotent. The target_data object in the call
-  // to match() may not be the same as target.
-  //
-  // match() can also be called by another rules (see cc/install).
+  // Note: match() is only called once but may not be followed by apply().
   //
   class rule
   {
   public:
-    virtual match_result
+    virtual bool
     match (action, target&, const string& hint) const = 0;
 
     virtual recipe
@@ -68,7 +36,7 @@ namespace build2
   public:
     file_rule () {}
 
-    virtual match_result
+    virtual bool
     match (action, target&, const string&) const override;
 
     virtual recipe
@@ -82,7 +50,7 @@ namespace build2
   public:
     alias_rule () {}
 
-    virtual match_result
+    virtual bool
     match (action, target&, const string&) const override;
 
     virtual recipe
@@ -96,7 +64,7 @@ namespace build2
   public:
     fsdir_rule () {}
 
-    virtual match_result
+    virtual bool
     match (action, target&, const string&) const override;
 
     virtual recipe
@@ -124,7 +92,7 @@ namespace build2
   public:
     fallback_rule () {}
 
-    virtual match_result
+    virtual bool
     match (action, target&, const string&) const override
     {
       return true;
-- 
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