Start getting the coercion infrastructure in place; it complains abou…

…t the (many) cases it doesn't know.

src/QAST/Compiler.nqp

@@ -146,6 +146,40 @@ class QAST::Compiler is HLL::Compiler {
         $ops;
     }
 
+    method coerce($qast, $desired) {
+        my $result := self.infer_type($qast.result());
+        if $result eq $desired {
+            # Exact match
+            return $qast;
+        }
+        elsif nqp::lc($result) eq $desired {
+            # The result is in a register, and our desired type allows
+            # both registers and literals.
+            return $qast;
+        }
+        else {
+            pir::die("Coercion from '$result' to '$desired' NYI");
+        }
+    }
+
+    method infer_type($inferee) {
+        if nqp::substr($inferee, 0, 1) eq '$' {
+            nqp::substr($inferee, 1, 1)
+        }
+        elsif nqp::substr($inferee, 0, 6) eq 'utf8:"' || nqp::substr($inferee, 0, 6) eq 'ucs4:"' {
+            "s"
+        }
+        elsif nqp::index($inferee, ".", 0) > 0 {
+            "n"
+        }
+        elsif +$inferee eq $inferee {
+            "i"
+        }
+        else {
+            pir::die("Cannot infer type from '$inferee'");
+        }
+    }
+
     multi method as_post(QAST::Regex $node) {
         my $ops := self.post_new('Ops');
         my $prefix := self.unique('rx') ~ '_';

src/QAST/Operations.nqp

@@ -58,15 +58,17 @@ class QAST::Operations {
 
             # Build the arguments list.
             # XXX keyed
-            # XXX coercions/boxings/unboxings
-            if +$op.list != +@arg_types {
+            my $num_args := +$op.list;
+            my $i := 0;
+            if +@arg_types != $num_args {
                 pir::die("Operation '" ~ $op.op ~ "' requires " ~
-                    +@arg_types ~ " operands, but got " ~ +$op.list);
+                    +@arg_types ~ " operands, but got $num_args");
             }
-            for $op.list {
-                my $post := $qastcomp.as_post($_);
+            while $i < $num_args {
+                my $post := $qastcomp.coerce($qastcomp.as_post($op.list[$i]), @arg_types[$i]);
                 $ops.push($post);
                 @args.push($post.result);
+                $i := $i + 1;
             }
 
             # If we have an integer as the return type, find the arg that