[dotnet] Add experimental support for :scope('outer') to PAST::Var (c…

…urious to see how pmichaud++ reacts), which does a lexical lookup but skipping the current scope. Currently, bind not supported, and of course :isdecl is invalid.

dotnet/compiler/PAST2DNSTCompiler.pm

@@ -832,6 +832,14 @@ our multi sub dnst_for(PAST::Var $var) {
             return emit_lexical_lookup($var.name);
         }
     }
+    elsif $scope eq 'outer' {
+        if $var.isdecl {
+            pir::die("Cannot use isdecl when scope is 'outer'.");
+        }
+        else {
+            return emit_outer_lexical_lookup($var.name);
+        }
+    }
     elsif $scope eq 'contextual' {
         if $var.isdecl {
             return declare_lexical($var);
@@ -1025,6 +1033,20 @@ sub emit_lexical_lookup($name) {
     $lookup
 }
 
+# Emits a lookup of a lexical in a scope outside the present one.
+sub emit_outer_lexical_lookup($name) {
+    if $*BIND_CONTEXT {
+        pir::die("Cannot bind to something using scope 'outer'.");
+    }
+    my $lookup := DNST::MethodCall.new(
+        :on('Ops'), :name('get_lex_skip_current'),
+        :type('RakudoObject'),
+        'TC',
+        DNST::Literal.new( :value($name), :escape(1) )
+    );
+    $lookup
+}
+
 # Emits a lookup of a dynamic var.
 sub emit_dynamic_lookup($name) {
     my $lookup := DNST::MethodCall.new(

dotnet/runtime/Runtime/Ops.cs

@@ -299,7 +299,7 @@ public static RakudoObject coerce_str_to_num(ThreadContext TC, RakudoObject Str,
         /// <summary>
         /// Gets a lexical variable of the given name.
         /// </summary>
-        /// <param name="i"></param>
+        /// <param name="TC"></param>
         /// <param name="name"></param>
         /// <returns></returns>
         public static RakudoObject get_lex(ThreadContext TC, string Name)
@@ -315,10 +315,30 @@ public static RakudoObject get_lex(ThreadContext TC, string Name)
             throw new InvalidOperationException("No variable " + Name + " found in the lexical scope");
         }
 
+        /// <summary>
+        /// Gets a lexical variable of the given name, but skips the current
+        /// scope.
+        /// </summary>
+        /// <param name="TC"></param>
+        /// <param name="name"></param>
+        /// <returns></returns>
+        public static RakudoObject get_lex_skip_current(ThreadContext TC, string Name)
+        {
+            var CurContext = TC.CurrentContext.Outer;
+            while (CurContext != null)
+            {
+                int Index;
+                if (CurContext.LexPad.SlotMapping.TryGetValue(Name, out Index))
+                    return CurContext.LexPad.Storage[Index];
+                CurContext = CurContext.Outer;
+            }
+            throw new InvalidOperationException("No variable " + Name + " found in the lexical scope");
+        }
+
         /// <summary>
         /// Binds the given value to a lexical variable of the given name.
         /// </summary>
-        /// <param name="i"></param>
+        /// <param name="TC"></param>
         /// <param name="name"></param>
         /// <returns></returns>
         public static RakudoObject bind_lex(ThreadContext TC, string Name, RakudoObject Value)