RakuAST: make single part setting lookups work

The multi-part one still fails, but that's code in the resolver that
will need closer scrutiny

src/Raku/ast/type.rakumod

@@ -76,12 +76,18 @@ class RakuAST::Type::Simple
     }
 }
 
-# A simple type name, e.g. Int, Foo::Bar, etc. that should be looked up in the
+# A simple type name, e.g. Int, IO::Path, etc. that should be looked up in the
 # setting.
 class RakuAST::Type::Setting
   is RakuAST::Type::Simple
 {
-    # TODO limit lookup to setting
+    method resolve-with(RakuAST::Resolver $resolver) {
+        my $resolved := $resolver.resolve-name-constant-in-setting(self.name);
+        if $resolved {
+            self.set-resolution($resolved);
+        }
+        Nil
+    }
 }
 
 class RakuAST::Type::Derived

t/12-rakuast/types.rakutest

@@ -140,7 +140,6 @@ subtest 'Single-part type from the setting' => {
     my \SETTING-Date := Date;
     for 'AST', $ast, 'Str', $deparsed, 'Raku', EVAL($raku) -> $type, $it {
         my class Date { }
-        todo "no actual lookup in SETTING only yet";
         is-deeply EVAL($it), SETTING-Date,
           "$type: did we get the setting version";
     }