Fix inconsistency with $$ in hooks.

Fixes #1914

`$$` says it refers to the pre-conversion value, but that's not true
within a hook. This fixes that so that `$$` always refers to the
pre-conversion value.

spicy/toolchain/src/compiler/codegen/codegen.cc

@@ -636,7 +636,7 @@ hilti::declaration::Function* CodeGen::compileHook(const type::Unit& unit, const
             params.push_back(builder()->parameter("__excpt", builder()->typeString(), hilti::parameter::Kind::In));
     }
     else if ( original_field_type ) {
-        params.push_back(builder()->parameter("__dd", field->itemType()->type(), hilti::parameter::Kind::In));
+        params.push_back(builder()->parameter("__dd", field->ddType()->type(), hilti::parameter::Kind::In));
 
         // Pass on captures for fields of type regexp, which are the only
         // ones that have it (for vector of regexps, it wouldn't be clear what

spicy/toolchain/src/compiler/codegen/parser-builder.cc

@@ -2470,7 +2470,7 @@ void ParserBuilder::newValueForField(const production::Meta& meta, Expression* v
     if ( field->emitHook() ) {
         beforeHook();
 
-        Expressions args = {value};
+        Expressions args = {dd};
 
         if ( field->originalType()->type()->isA<hilti::type::RegExp>() && ! field->isContainer() ) {
             if ( state().captures )

spicy/toolchain/src/compiler/resolver.cc

@@ -267,18 +267,15 @@ struct VisitorPass2 : visitor::MutatingPostOrder {
         if ( n->unitFieldIndex() && ! n->dd() ) {
             auto unit_field = context()->lookup(n->unitFieldIndex())->as<type::unit::item::Field>();
 
-            QualifiedType* dd = nullptr;
+            QualifiedType* dd = unit_field->ddType();
 
             if ( n->hookType() == declaration::hook::Type::ForEach ) {
-                dd = unit_field->ddType();
                 if ( ! dd || ! dd->isResolved() )
                     return;
 
                 // Validator will catch if the type is not a container.
                 dd = dd->type()->elementType();
             }
-            else
-                dd = unit_field->itemType();
 
             if ( dd && dd->isResolved() ) {
                 auto dd_ = QualifiedType::createExternal(context(), dd->type(), dd->constness());

tests/Baseline/spicy.types.unit.dd-hook-type/output

@@ -0,0 +1,3 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+True
+True

tests/spicy/types/unit/dd-hook-type.spicy

@@ -0,0 +1,14 @@
+# @TEST-EXEC: echo '00' | spicy-driver -d %INPUT >output
+# @TEST-EXEC: btest-diff output
+
+module DDConsistency;
+
+public type Data = unit {
+    x: uint8 &convert=($$ + 5) &requires=($$ < 50) {
+        print $$ < 50; # Should print True since it got through the requires
+    }
+
+    y: uint8 &convert=($$ == 48) &requires=($$ < 50) {
+        print $$ == 48; # Should succeed compiling since $$ is uint8 still
+    }
+};