From f4addf6d170223bfcc86fc0622a329a7173ab3ab Mon Sep 17 00:00:00 2001
From: Stefan O'Rear <stefanor@cox.net>
Date: Tue, 20 Jul 2010 23:19:19 -0700
Subject: [PATCH] Upward type inference for let

---
 CgOp.pm    | 14 +++++++-------
 CodeGen.pm |  6 +++---
 Decl.pm    |  2 +-
 Op.pm      |  5 ++---
 Sig.pm     |  3 +--
 Unit.pm    |  2 +-
 6 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/CgOp.pm b/CgOp.pm
index 40f85372..4d90c859 100644
--- a/CgOp.pm
+++ b/CgOp.pm
@@ -249,7 +249,7 @@ use warnings;
 
     sub methodcall {
         my ($obj, $name, @args) = @_;
-        let($obj, 'Variable', sub {
+        let($obj, sub {
             CgOp::Primitive->new(op => [ 'call_method', 1, $name, scalar @args ],
                 zyg => [ fetch($_[0]), $_[0], @args ])});
     }
@@ -272,7 +272,7 @@ use warnings;
         } else {
             my $n = shift;
             my $t = shift;
-            letn($n, $t, null($t), withtypes(@_));
+            letn($n, null($t), withtypes(@_));
         }
     }
 
@@ -337,9 +337,9 @@ use warnings;
     }
 
     sub letn {
-        my ($name, $type, $value, @stuff) = @_;
+        my ($name, $value, @stuff) = @_;
         prog(
-            CgOp::Primitive->new(op => [ 'push_let', $name, $type ],
+            CgOp::Primitive->new(op => [ 'push_let', $name ],
                 zyg => [ $value ]),
             @stuff,
             sink(CgOp::Primitive->new(op => [ 'pop_let', $name ])));
@@ -362,9 +362,9 @@ use warnings;
 
     my $nextlet = 0;
     sub let {
-        my ($head, $type, $bodyf) = @_;
+        my ($head, $bodyf) = @_;
         my $v = ($nextlet++);
-        letn($v, $type, $head, $bodyf->(letvar($v)));
+        letn($v, $head, $bodyf->(letvar($v)));
     }
 }
 
@@ -408,7 +408,7 @@ use warnings;
                 if (_okdelay($op->zyg->[scalar @sofar])) {
                     $_recurse->(@sofar, $op->zyg->[scalar @sofar]);
                 } else {
-                    let($op->zyg->[scalar @sofar], 'XXX',
+                    let($op->zyg->[scalar @sofar],
                         sub { $_recurse->(@sofar, $_[0]) });
                 }
             };
diff --git a/CodeGen.pm b/CodeGen.pm
index e231343a..09357c15 100644
--- a/CodeGen.pm
+++ b/CodeGen.pm
@@ -208,9 +208,9 @@ use 5.010;
     }
 
     sub push_let {
-        my ($self, $which, $ty) = @_;
+        my ($self, $which) = @_;
         my $var = "let!${which}!" . ($self->letdepths->{$which}++);
-        $self->lex2type->{$var} = $ty;
+        $self->lex2type->{$var} = $self->stacktype->[-1];
         $self->rawlexput($var);
     }
 
@@ -558,7 +558,7 @@ use 5.010;
         my ($self, $body) = @_;
         $self->peek_let('protopad');
         $self->clr_new('Frame', 1);
-        $self->push_let('protopad', 'Frame');
+        $self->push_let('protopad');
         push @{ $self->bodies }, $body;
     }
 
diff --git a/Decl.pm b/Decl.pm
index 9a590b9d..ac27dd32 100644
--- a/Decl.pm
+++ b/Decl.pm
@@ -221,7 +221,7 @@ use CgOp;
 
         $self->body->outer($body);
 
-        CgOp::letn("how", "Variable",
+        CgOp::letn("how",
             CgOp::methodcall(CgOp::scopedlex("ClassHOW"), "new",
                 CgOp::wrap(CgOp::clr_string($self->name // 'ANON'))),
 
diff --git a/Op.pm b/Op.pm
index 30fdacd9..9d2b1c7a 100644
--- a/Op.pm
+++ b/Op.pm
@@ -141,7 +141,7 @@ use CgOp;
 
     sub code {
         my ($self, $body) = @_;
-        CgOp::let($self->receiver->code($body), 'Variable', sub {
+        CgOp::let($self->receiver->code($body), sub {
             CgOp::methodcall(CgOp::newscalar(CgOp::how(CgOp::fetch($_[0]))),
                 $self->name, $_[0], map { $_->code($body) }
                     @{ $self->positionals })});
@@ -243,8 +243,7 @@ use CgOp;
         my $acc = (shift @r)->code($body);
 
         for (@r) {
-            $acc = CgOp::let($_->code($body), 'Variable',
-                sub { $self->red2($_[0], $acc) });
+            $acc = CgOp::let($_->code($body), sub { $self->red2($_[0], $acc) });
         }
 
         $acc;
diff --git a/Sig.pm b/Sig.pm
index 31a11018..7f48497d 100644
--- a/Sig.pm
+++ b/Sig.pm
@@ -42,8 +42,7 @@ use 5.010;
         if ($self->slurpy) {
             $self->target->binder(
                 CgOp::let(CgOp::rawnew('DynObject', CgOp::getfield('klass',
-                            CgOp::cast('DynObject', CgOp::fetch(CgOp::scopedlex('List'))))),
-                    'DynObject', sub {
+                            CgOp::cast('DynObject', CgOp::fetch(CgOp::scopedlex('List'))))), sub {
                     my $do = shift;
                     CgOp::prog(
                         CgOp::setindex('flat', CgOp::getfield('slots', $do),
diff --git a/Unit.pm b/Unit.pm
index fd329c47..b18c66d7 100644
--- a/Unit.pm
+++ b/Unit.pm
@@ -20,7 +20,7 @@ use 5.010;
         my ($self) = @_;
         $self->mainline->outer($self->setting) if $self->setting;
         CodeGen->new(name => 'BOOT', entry => 1,
-            ops => CgOp::letn('protopad', 'Frame',
+            ops => CgOp::letn('protopad',
                 CgOp::cast('Frame', CgOp::fetch(CgOp::pos(0))),
                 CgOp::return(
                     CgOp::newscalar(