Implement use experimental :rakuast

This pretty hacky approach fetches the RakuAST type object at the
end of the core.c compilation, and stashes that with bindcurhllsym.
It then replaces the CORE::<RakuAST> entry with a subclass of Nil,
causing all lookups for RakuAST classes to fail from thereon with a
nice informative message.

It also lexically enables RakuAST again in the 6.e Formatter class
to keep that working and puts in provisions to let dd work with
RakuAST classes.

And it adds an entry in lib/experimental that basically makes the
original RakuAST type object visible again and make everything
work as if the interface was completely stable.

Also add comments on when to remove the code and fix the
RakuAST test files by adding 'use experimental :rakuast' to them.

This also moves src/core.c/RakuAST/Deparse.pm6 to
lib/RakuAST/Deparse.rakumod and allow for it to work with
late loading.

src/core.c/RakuAST/Deparse.pm6 → lib/RakuAST/Deparse.rakumod

@@ -6,6 +6,13 @@
 # method expects an instance if a subclass of a RakuAST::Node as the first
 # positional parameter.
 
+# This code can be removed once RakuAST is stable and
+#   use experimental :rakuast;
+# is no longer necessary to be able to access the RakuAST classes
+# and their functionality.
+use nqp;
+my constant RakuAST = nqp::gethllsym('Raku','RakuAST');
+
 class RakuAST::Deparse {
     has str $.before-comma = ' ';
     has str $.after-comma  = ' ';

lib/experimental.rakumod

@@ -1,5 +1,19 @@
 use nqp;
 
+package EXPORT::rakuast {
+    # This code can be removed once RakuAST is stable and
+    #   use experimental :rakuast;
+    # is no longer necessary to be able to access the RakuAST classes
+    # and their functionality.
+    my \RakuAST := nqp::getcurhllsym('RakuAST');
+
+    require ::("RakuAST::Deparse");
+    use nqp;
+    nqp::bindcurhllsym('DEPARSE',::("RakuAST::Deparse"));
+
+    OUR::<RakuAST> := RakuAST;
+}
+
 package EXPORT::cached {
     multi sub trait_mod:<is>(Routine $r, :$cached!) {
         my %cache;

src/core.c/Any.pm6

@@ -592,10 +592,14 @@ sub dd(|c) {  # is implementation-detail
 
     my Mu $args := nqp::p6argvmarray();
     if nqp::elems($args) {
+        # This code can be removed once RakuAST is stable and
+        #   use experimental :rakuast;
+        # is no longer necessary to be able to access the RakuAST classes
+        # and their functionality.
         while $args {
             my $var  := nqp::shift($args);
             if nqp::istype($var,RakuAST::Node) {
-                note $var.DEPARSE.chomp;
+                Rakudo::Internals.DEPARSE($var);
             }
             else {
                 my $name := ! nqp::istype($var.VAR, Failure) && try $var.VAR.name;

src/core.c/Stash.pm6

@@ -24,6 +24,13 @@ my class Stash { # declared in BOOTSTRAP
                ContainerDescriptor::BindHashKey.new(Mu, self, $key)
              )
     }
+
+    method !fail-not-found($key) {
+        (self.Str eq 'must-use-experimental-rakuast'
+          ?? "Must do a 'use experimental :rakuast' to access RakuAST::$key.substr(1)"
+          !! "Could not find symbol '$key' in '{self}'"
+        ).Failure
+    }
     multi method AT-KEY(Stash:D: Str() $key, :$global_fallback!) is raw {
         my \storage := nqp::getattr(self,Map,'$!storage');
         nqp::if(
@@ -34,7 +41,7 @@ my class Stash { # declared in BOOTSTRAP
             nqp::if(
               nqp::existskey(GLOBAL.WHO,$key),
               nqp::atkey(GLOBAL.WHO,$key),
-              "Could not find symbol '$key' in '{self}'".Failure
+              self!fail-not-found($key)
             ),
             nqp::p6scalarfromdesc(
               ContainerDescriptor::BindHashKey.new(Mu, self, $key)

src/core.c/core_epilogue.pm6

@@ -135,6 +135,33 @@ BEGIN .^compose for
 
 BEGIN Metamodel::ClassHOW.exclude_parent(Mu);
 
+# This code can be removed once RakuAST is stable and
+#   use experimental :rakuast;
+# is no longer necessary to be able to access the RakuAST classes
+# and their functionality.
+{
+    my Mu $ctx := nqp::getattr(CORE::, PseudoStash, '$!ctx');
+    my class must-use-experimental-rakuast is Nil { }
+    until nqp::isnull($ctx) {
+        my $pad := nqp::ctxlexpad($ctx);
+        if nqp::existskey($pad, 'CORE-SETTING-REV') {
+            nqp::bindcurhllsym('RakuAST',RakuAST);
+            nqp::bindkey($pad,'RakuAST',must-use-experimental-rakuast);
+            last;
+        }
+        $ctx := nqp::ctxouterskipthunks($ctx);
+    }
+}
+augment class Rakudo::Internals {
+    # This code needs to live late, as at compilation time of
+    # "sub dd", the ::() lookup doesn't work yet
+    method DEPARSE($var) {
+        require ::("RakuAST::Deparse");
+        nqp::bindcurhllsym("DEPARSE",::("RakuAST::Deparse"));
+        note $var.DEPARSE.chomp;
+    }
+}
+
 {YOU_ARE_HERE}
 
 # vim: expandtab shiftwidth=4

src/core.c/core_prologue.pm6

@@ -10,7 +10,6 @@ my class List { ... }
 my class Map { ... }
 my class Match { ... }
 my class Failure { ... }
-my class RakuAST::Deparse { ... }
 my class Rakudo::Deprecations { ... }
 my class Rakudo::Internals { ... }
 my class Rakudo::Internals::JSON { ... }
@@ -44,9 +43,6 @@ BEGIN nqp::bindhllsym('Raku', 'Iterable', Iterable);
 nqp::bindhllsym('Raku', 'Iterable', Iterable);
 nqp::bindhllsym('Raku', 'Failure', Failure);
 
-# Make deparsing possible with the .DEPARSE method from NQP
-nqp::bindhllsym('Raku','DEPARSE',RakuAST::Deparse);
-
 BEGIN {
     # Ensure routines with traits using mixins applied to them typecheck as Callable.
     Code.^add_role: Callable;

src/core.e/Formatter.pm6

@@ -99,6 +99,11 @@ grammar Formatter::Syntax {
 }
 
 class Formatter {
+    # This code can be removed once RakuAST is stable and
+    #   use experimental :rakuast;
+    # is no longer necessary to be able to access the RakuAST classes
+    # and their functionality.
+    my constant RakuAST = nqp::getcurhllsym('RakuAST');
 
     # class to be used with Grammar to turn format into array of pieces of code
     class Actions {
@@ -446,7 +451,7 @@ class Formatter {
 
             my $size = size($/);
             my $ast  = ast-call-sub("unsigned-int", parameter($/));
-            
+
             # handle zero padding / left / right justification
             if $size {
                 $ast = ast-call-sub(

t/12-rakuast/call.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 18;

t/12-rakuast/circumfix.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 7;

t/12-rakuast/code.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 11;

t/12-rakuast/contextualizer.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 4;

t/12-rakuast/errors.t

@@ -1,3 +1,4 @@
+use experimental :rakuast;
 use Test;
 
 plan 1;

t/12-rakuast/literals.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 8;

t/12-rakuast/meta-operators.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 4;

t/12-rakuast/name.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 6;

t/12-rakuast/operators.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 23;

t/12-rakuast/package.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 11;

t/12-rakuast/pair.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 6;

t/12-rakuast/regex.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 41;

t/12-rakuast/signature.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 14;

t/12-rakuast/statement-mods.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 13;

t/12-rakuast/statementprefixes.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 15;

t/12-rakuast/statements.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 26; # Do not change this file to done-testing

t/12-rakuast/strings.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 13;

t/12-rakuast/stubs.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 6;

t/12-rakuast/terms.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 11;

t/12-rakuast/var.t

@@ -1,4 +1,5 @@
 use MONKEY-SEE-NO-EVAL;
+use experimental :rakuast;
 use Test;
 
 plan 37;

tools/build/install-core-dist.raku

@@ -14,6 +14,7 @@ my %provides =
     "snapper"                       => "lib/snapper.rakumod",
     "safe-snapper"                  => "lib/safe-snapper.rakumod",
     "BUILDPLAN"                     => "lib/BUILDPLAN.rakumod",
+    "RakuAST::Deparse"              => "lib/RakuAST/Deparse.rakumod",
 ;
 
 %provides<NativeCall::Dispatcher> = "lib/NativeCall/Dispatcher.rakumod"

tools/templates/6.c/core_sources

@@ -251,5 +251,4 @@ src/core.c/WrappedJSObject.pm6)@
 src/core.c/Rakudo/Metaops.pm6
 src/core.c/Rakudo/Internals/PostcircumfixAdverbs.pm6
 src/core.c/unicodey.pm6
-src/core.c/RakuAST/Deparse.pm6
 src/core.c/core_epilogue.pm6