Differentiate required and optional implicit topic

When we have `for @A { }` then there is no need for the `$_` parameter to be optional, since we know we'll always be invoking the block with a parameter. This should lead to slightly more compact/efficient code for such cases, and will make the static optimizer's job easier with regard to having to try and track outer lexical accesses.
rakudo · Jan 3, 2019 · 64d08ad · 64d08ad
1 parent f741374
commit 64d08ad
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Showing 2 changed files with 23 additions and 14 deletions.
diff --git a/src/Perl6/Actions.nqp b/src/Perl6/Actions.nqp
@@ -1705,10 +1705,11 @@ class Perl6::Actions is HLL::Actions does STDActions {
             }
             else {
                 if $*IMPLICIT {
+                    my $optional := $*IMPLICIT == 1;
                     @params.push(hash(
-                        :variable_name('$_'), :optional(1),
+                        :variable_name('$_'), :$optional,
                         :nominal_type($*W.find_symbol(['Mu'])),
-                        :default_from_outer(1), :is_raw(1),
+                        :default_from_outer($optional), :is_raw(1),
                     ));
                 }
                 elsif !$block.symbol('$_') {

diff --git a/src/Perl6/Grammar.nqp b/src/Perl6/Grammar.nqp
@@ -981,13 +981,18 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
         || { $/.typed_panic( 'X::Syntax::Confused', reason => "Confused" ) }
     }
 
-    token xblock($*IMPLICIT = 0) {
+    # Options for xblock/block implicit topic.
+    my $PBLOCK_NO_TOPIC := 0;
+    my $PBLOCK_OPTIONAL_TOPIC := 1;
+    my $PBLOCK_REQUIRED_TOPIC := 2;
+
+    token xblock($*IMPLICIT = $PBLOCK_NO_TOPIC) {
         :my $*GOAL := '{';
         :my $*BORG := {};
         <EXPR> <.ws> <pblock($*IMPLICIT)>
     }
 
-    token pblock($*IMPLICIT = 0) {
+    token pblock($*IMPLICIT = $PBLOCK_NO_TOPIC) {
         :my $*DECLARAND := $*W.stub_code_object('Block');
         :my $*CODE_OBJECT := $*DECLARAND;
         :my $*SIG_OBJ;
@@ -1111,22 +1116,25 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
 
     rule statement_control:sym<if> {
         $<sym>=[if|with]<.kok> {}
-        <xblock(so ~$<sym>[0] ~~ /with/)>
+        <xblock(~$<sym>[0] ~~ /with/ ?? $PBLOCK_REQUIRED_TOPIC !! $PBLOCK_NO_TOPIC)>
         [
             [
             | 'else'\h*'if' <.typed_panic: 'X::Syntax::Malformed::Elsif'>
             | 'elif' { $/.typed_panic('X::Syntax::Malformed::Elsif', what => "elif") }
             | $<sym>='elsif' <xblock>
-            | $<sym>='orwith' <xblock(1)>
+            | $<sym>='orwith' <xblock($PBLOCK_REQUIRED_TOPIC)>
             ]
         ]*
         {}
-        [ 'else' <else=.pblock(so ~$<sym>[-1] ~~ /with/)> ]?
+        [
+            'else'
+            <else=.pblock(~$<sym>[-1] ~~ /with/ ?? $PBLOCK_REQUIRED_TOPIC !! $PBLOCK_NO_TOPIC)>
+        ]?
     }
 
     rule statement_control:sym<unless> {
         $<sym>='unless'<.kok>
-        <xblock(0)> # 0 means we're not parsing `without`
+        <xblock($PBLOCK_NO_TOPIC)> # 0 means we're not parsing `without`
         [ <!before [els[e|if]|orwith]» >
             || $<wrong-keyword>=[els[e|if]|orwith]» {}
                 <.typed_panic: 'X::Syntax::UnlessElse',
@@ -1137,7 +1145,7 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
 
     rule statement_control:sym<without> {
         $<sym>='without'<.kok>
-        <xblock(1)> # 1 means we're not parsing `unless`
+        <xblock($PBLOCK_REQUIRED_TOPIC)> # 1 means we're not parsing `unless`
         [ <!before [els[e|if]|orwith]» >
             || $<wrong-keyword>=[els[e|if]|orwith]» {}
                 <.typed_panic: 'X::Syntax::WithoutElse',
@@ -1167,7 +1175,7 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
             <.typed_panic: 'X::Syntax::P5'> ]?
         [ <?before '(' <.EXPR>? ';' <.EXPR>? ';' <.EXPR>? ')' >
             <.obs('C-style "for (;;)" loop', '"loop (;;)"')> ]?
-        <xblock(1)>
+        <xblock($PBLOCK_REQUIRED_TOPIC)>
     }
 
     rule statement_control:sym<whenever> {
@@ -1180,7 +1188,7 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
         || <.typed_panic('X::Comp::WheneverOutOfScope')>
         ]
         { $*WHENEVER_COUNT++ }
-        <xblock(1)>
+        <xblock($PBLOCK_REQUIRED_TOPIC)>
     }
 
     rule statement_control:sym<foreach> {
@@ -1341,7 +1349,7 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
     }
 
     rule statement_control:sym<given> {
-        <sym><.kok> <xblock(1)>
+        <sym><.kok> <xblock($PBLOCK_REQUIRED_TOPIC)>
     }
     rule statement_control:sym<when> {
         <sym><.kok> <xblock>
@@ -2964,7 +2972,7 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
     }
     rule trait_mod:sym<hides>   { <sym> [ <typename> || <.bad_trait_typename>] }
     rule trait_mod:sym<does>    { <sym> [ <typename> || <.bad_trait_typename>] }
-    rule trait_mod:sym<will>    { <sym> [ <identifier> || <.panic: 'Invalid name'>] <pblock(1)> }
+    rule trait_mod:sym<will>    { <sym> [ <identifier> || <.panic: 'Invalid name'>] <pblock($PBLOCK_OPTIONAL_TOPIC)> }
     rule trait_mod:sym<of>      { <sym> [ <typename> || <.bad_trait_typename>] }
     rule trait_mod:sym<returns> { <sym> [ <typename> || <.bad_trait_typename>]
                                   || 'return' <.panic: 'Invalid trait modifier (did you mean \'returns\'?)'> }
@@ -3548,7 +3556,7 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
     token circumfix:sym<« »> { :dba('shell-quote words') '«' ~ '»' <nibble(self.quote_lang(self.slang_grammar('Quote'), "«", "»", ['qq', 'ww', 'v']))> }
     token circumfix:sym<{ }> {
         :my $*FAKE_INFIX_FOUND := 0;
-        <?[{]> <pblock(1)>
+        <?[{]> <pblock($PBLOCK_OPTIONAL_TOPIC)>
         {
             $*BORG<block> := $<pblock>
         }