From f11ad52fdacb47a529474807eb498cff5ee2ca55 Mon Sep 17 00:00:00 2001
From: jnthn <jnthn@jnthn.net>
Date: Wed, 25 Mar 2009 16:02:17 +0100
Subject: [PATCH] Implement START statements (not terms yet). Add
 S04-closure-traits/start.t to spectest.data.

---
 src/parser/actions.pm | 41 ++++++++++++++++++++++++++++++++++-------
 src/parser/grammar.pg |  7 +++++++
 t/spectest.data       |  1 +
 3 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/src/parser/actions.pm b/src/parser/actions.pm
index 102a9fe35bf..2915e0a8217 100644
--- a/src/parser/actions.pm
+++ b/src/parser/actions.pm
@@ -403,6 +403,26 @@ method begin_statement($/) {
     make PAST::Block.new();
 }
 
+method start_statement($/) {
+    # Create block.
+    my $past := $( $<block> );
+    $past.blocktype('immediate');
+    declare_implicit_routine_vars($past);
+
+    # Mark block as needing to load state.
+    our @?BLOCK;
+    block_has_state(@?BLOCK[0]);
+
+    # We now need to emit code to run the block only once, and store the
+    # result. We'll just piggy-back off state vars.
+    make PAST::Var.new(
+        :scope('state'),
+        :name($past.unique('start_block_')),
+        :viviself($past),
+        :isdecl(1)
+    );
+}
+
 method end_statement($/) {
     my $past := $( $<block> );
     $past.blocktype('declaration');
@@ -1888,13 +1908,7 @@ method scope_declarator($/) {
         else { $past.name('infix:,'); $past.pasttype('call'); }
         if $scope eq 'state' {
             $past<scopedecl> := $scope;
-            unless $block<needs_state_loaded> {
-                $block[0].push(PAST::Op.new(
-                    :pasttype('call'),
-                    :name('!state_var_init')
-                ));
-                $block<needs_state_loaded> := 1;
-            }
+            block_has_state($block);
         }
     }
     make $past;
@@ -3124,6 +3138,19 @@ sub prevent_null_return($block) {
     }
 }
 
+
+# This takes a block and ensures we emit code to load any associated state
+# (START blocks, state variables) at block entry.
+sub block_has_state($block) {
+    unless $block<needs_state_loaded> {
+        $block[0].push(PAST::Op.new(
+            :pasttype('call'),
+            :name('!state_var_init')
+        ));
+        $block<needs_state_loaded> := 1;
+    }
+}
+
 # Local Variables:
 #   mode: cperl
 #   cperl-indent-level: 4
diff --git a/src/parser/grammar.pg b/src/parser/grammar.pg
index 64ad3d30070..777ecaa788e 100644
--- a/src/parser/grammar.pg
+++ b/src/parser/grammar.pg
@@ -262,6 +262,7 @@ rule statement_control {
     | <for_statement> {*}                        #= for_statement
     | <use_statement> {*}                        #= use_statement
     | <begin_statement> {*}                      #= begin_statement
+    | <start_statement> {*}                      #= start_statement
     | <end_statement> {*}                        #= end_statement
     | <catch_statement> {*}                      #= catch_statement
     | <control_statement> {*}                    #= control_statement
@@ -345,6 +346,12 @@ rule begin_statement {
     {*}
 }
 
+rule start_statement {
+    $<sym>=[START]
+    <block>
+    {*}
+}
+
 rule end_statement {
     $<sym>=[END]
     <block>
diff --git a/t/spectest.data b/t/spectest.data
index 5c318694583..1628a7007fc 100644
--- a/t/spectest.data
+++ b/t/spectest.data
@@ -121,6 +121,7 @@ S03-operators/value_equivalence.t
 S04-blocks-and-statements/pointy-rw.t
 S04-blocks-and-statements/pointy.t
 S04-closure-traits/end.t
+S04-closure-traits/start.t
 S04-declarations/implicit-parameter.t
 S04-declarations/multiple.t
 S04-declarations/my.t