Fix access to anonymous bitfield element through a constant value.

Closes #1533.

spicy/toolchain/src/compiler/visitors/normalizer.cc

@@ -252,6 +252,29 @@ struct Visitor : public hilti::visitor::PostOrder<void, Visitor> {
         return {};
     }
 
+    void operator()(const operator_::unit::MemberConst& o, position_t p) {
+        auto unit = o.op0().type().tryAs<type::Unit>();
+        auto id = o.op1().tryAs<hilti::expression::Member>()->id();
+
+        if ( unit && id && ! unit->itemByName(id) ) {
+            // See if we got an anonymous bitfield with a member of that
+            // name. If so, rewrite the access to transparently refer to the
+            // member through the field's internal name.
+            if ( auto field_id = findBitsFieldID(unit->items(), id) ) {
+                auto access_field =
+                    operator_::unit::MemberConst::Operator().instantiate({o.op0(),
+                                                                             hilti::expression::Member(*field_id)},
+                                                                            o.meta());
+                auto access_bits =
+                    bitfield::Member::Operator().instantiate({std::move(access_field), o.op1()}, o.meta());
+
+                logChange(p.node, access_bits);
+                p.node = access_bits;
+                modified = true;
+            }
+        }
+    }
+
     void operator()(const operator_::unit::MemberNonConst& o, position_t p) {
         auto unit = o.op0().type().tryAs<type::Unit>();
         auto id = o.op1().tryAs<hilti::expression::Member>()->id();

tests/Baseline/spicy.types.bitfield.anonymous-field-const/output

@@ -0,0 +1,2 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+255

tests/spicy/types/bitfield/anonymous-field-const.spicy

@@ -0,0 +1,19 @@
+# @TEST-EXEC:  printf '\377' | spicy-driver %INPUT >output
+# @TEST-EXEC:  btest-diff output
+
+module foo;
+
+type X = unit {
+    : bitfield(8) {
+        a: 0..7;
+    };
+};
+
+type Y = unit(x: X) {
+    on %init { print x.a; }
+};
+
+public type Z = unit {
+    x: X;
+    y: Y(self.x);
+};