Use str constraint on various paths.

The goal being that we can stick a native `str` on the $name of the
QAST::Block.symbol method, which accounts for an overwhelming amount
of boxing in EVAL-heavy situations.

src/NQP/Actions.nqp

@@ -571,7 +571,7 @@ class NQP::Actions is HLL::Actions {
                 $ast.fallback( default_for( $<sigil> ) );
             }
             else {
-                my $name := ~@name.pop;
+                my str $name := ~@name.pop;
                 my int $is_lex := 0;
                 if $*IN_DECL eq 'variable' || $name eq '$_' || $name eq '$/' || $name eq '$¢'
                 || $name eq '$!' || $<twigil> eq '?' || ($is_lex := $*W.is_lexical($name)) {
@@ -604,14 +604,14 @@ class NQP::Actions is HLL::Actions {
         if $*SCOPE eq 'our' || $*SCOPE eq '' {
             $*W.install_package_symbol($*OUTERPACKAGE, $<name><identifier>, $PACKAGE);
             if +$<name><identifier> == 1 {
-                $*W.install_lexical_symbol($*W.cur_lexpad(), $<name><identifier>[0], $PACKAGE);
+                $*W.install_lexical_symbol($*W.cur_lexpad(), ~$<name><identifier>[0], $PACKAGE);
             }
         }
         elsif $*SCOPE eq 'my' {
             if +$<name><identifier> != 1 {
                 $<name>.CURSOR.panic("A my scoped package cannot have a multi-part name yet");
             }
-            $*W.install_lexical_symbol($*W.cur_lexpad(), $<name><identifier>[0], $PACKAGE);
+            $*W.install_lexical_symbol($*W.cur_lexpad(), ~$<name><identifier>[0], $PACKAGE);
         }
         else {
             $/.CURSOR.panic("$*SCOPE scoped packages are not supported");
@@ -1737,7 +1737,7 @@ class NQP::Actions is HLL::Actions {
         # then strip it off.
         else {
             my $path;
-            if $*W.is_lexical(@name[0]) {
+            if $*W.is_lexical(~@name[0]) {
                 try {
                     my $first := @name.shift();
                     $path := QAST::WVal.new( :value($*W.find_sym([$first])) );

src/NQP/Grammar.nqp

@@ -420,14 +420,14 @@ grammar NQP::Grammar is HLL::Grammar {
             if $*SCOPE eq 'our' || $*SCOPE eq '' {
                 $*W.install_package_symbol($*OUTERPACKAGE, $<name><identifier>, $*PACKAGE);
                 if +$<name><identifier> == 1 {
-                    $*W.install_lexical_symbol($OUTER, $<name><identifier>[0], $*PACKAGE);
+                    $*W.install_lexical_symbol($OUTER, ~$<name><identifier>[0], $*PACKAGE);
                 }
             }
             elsif $*SCOPE eq 'my' {
                 if +$<name><identifier> != 1 {
                     $<name>.CURSOR.panic("A my scoped package cannot have a multi-part name yet");
                 }
-                $*W.install_lexical_symbol($OUTER, $<name><identifier>[0], $*PACKAGE);
+                $*W.install_lexical_symbol($OUTER, ~$<name><identifier>[0], $*PACKAGE);
             }
             else {
                 $/.CURSOR.panic("$*SCOPE scoped packages are not supported");
@@ -881,4 +881,3 @@ grammar NQP::Regex is QRegex::P6Regex::Grammar {
         <quote_EXPR=.LANG('MAIN','quote_EXPR')>
     }
 }
-

src/NQP/World.nqp

@@ -180,7 +180,7 @@ class NQP::World is HLL::World {
 
     # Installs a lexical symbol. Takes a QAST::Block object, name and
     # the object to install.
-    method install_lexical_symbol($block, $name, $obj) {
+    method install_lexical_symbol($block, str $name, $obj) {
         $block.symbol($name, :scope('lexical'), :value($obj));
         $block[0].push(QAST::Var.new(
             :scope('lexical'), :name($name), :decl('static'), :value($obj)
@@ -552,19 +552,19 @@ class NQP::World is HLL::World {
 
     # Checks if the given name is known anywhere in the lexpad
     # and with lexical scope.
-    method is_lexical($name) {
+    method is_lexical(str $name) {
         self.is_scope($name, 'lexical')
     }
 
     # Checks if the given name is known anywhere in the lexpad
     # and with package scope.
-    method is_package($name) {
+    method is_package(str $name) {
         self.is_scope($name, 'package')
     }
 
     # Checks if a given name is known in the lexpad anywhere
     # with the specified scope.
-    method is_scope($name, $wanted_scope) {
+    method is_scope(str $name, $wanted_scope) {
         my $i := +@!BLOCKS;
         while $i > 0 {
             $i := $i - 1;
@@ -577,7 +577,7 @@ class NQP::World is HLL::World {
     }
 
     # Gets the type of a lexical.
-    method lexical_type($name) {
+    method lexical_type(str $name) {
         my $i := +@!BLOCKS;
         while $i > 0 {
             $i := $i - 1;
@@ -609,7 +609,7 @@ class NQP::World is HLL::World {
         # If it's a single-part name, look through the lexical
         # scopes.
         if +@name == 1 {
-            my $final_name := @name[0];
+            my str $final_name := ~@name[0];
             my $i := +@!BLOCKS;
             while $i > 0 {
                 $i := $i - 1;
@@ -625,8 +625,8 @@ class NQP::World is HLL::World {
         # in GLOBALish.
         my $result := $*GLOBALish;
         if +@name >= 2 {
-            my $first := @name[0];
-            my $i := +@!BLOCKS;
+            my str $first := ~@name[0];
+            my int $i := +@!BLOCKS;
             while $i > 0 {
                 $i := $i - 1;
                 my %sym := @!BLOCKS[$i].symbol($first);