GDScript: Fix resolution of dictionary keys

There was a mixup between String and StringName keys. Now they're
clearly separated. This also means you have to consider which type
you're using for the dictionary keys and how you are accessing them.

modules/gdscript/gdscript_analyzer.cpp

@@ -2621,25 +2621,6 @@ void GDScriptAnalyzer::reduce_subscript(GDScriptParser::SubscriptNode *p_subscri
 
 	GDScriptParser::DataType result_type;
 
-	// Reduce index first. If it's a constant StringName, use attribute instead.
-	if (!p_subscript->is_attribute) {
-		if (p_subscript->index == nullptr) {
-			return;
-		}
-		reduce_expression(p_subscript->index);
-
-		if (p_subscript->index->is_constant && p_subscript->index->reduced_value.get_type() == Variant::STRING_NAME) {
-			GDScriptParser::IdentifierNode *attribute = parser->alloc_node<GDScriptParser::IdentifierNode>();
-			// Copy location for better error message.
-			attribute->start_line = p_subscript->index->start_line;
-			attribute->end_line = p_subscript->index->end_line;
-			attribute->leftmost_column = p_subscript->index->leftmost_column;
-			attribute->rightmost_column = p_subscript->index->rightmost_column;
-			p_subscript->is_attribute = true;
-			p_subscript->attribute = attribute;
-		}
-	}
-
 	if (p_subscript->is_attribute) {
 		if (p_subscript->attribute == nullptr) {
 			return;
@@ -2682,7 +2663,10 @@ void GDScriptAnalyzer::reduce_subscript(GDScriptParser::SubscriptNode *p_subscri
 			}
 		}
 	} else {
-		// Index was already reduced before.
+		if (p_subscript->index == nullptr) {
+			return;
+		}
+		reduce_expression(p_subscript->index);
 
 		if (p_subscript->base->is_constant && p_subscript->index->is_constant) {
 			// Just try to get it.

modules/gdscript/gdscript_compiler.cpp

@@ -680,9 +680,9 @@ GDScriptCodeGenerator::Address GDScriptCompiler::_parse_expression(CodeGen &code
 				name = subscript->attribute->name;
 				named = true;
 			} else {
-				if (subscript->index->type == GDScriptParser::Node::LITERAL && static_cast<const GDScriptParser::LiteralNode *>(subscript->index)->value.get_type() == Variant::STRING) {
+				if (subscript->index->is_constant && subscript->index->reduced_value.get_type() == Variant::STRING_NAME) {
 					// Also, somehow, named (speed up anyway).
-					name = static_cast<const GDScriptParser::LiteralNode *>(subscript->index)->value;
+					name = subscript->index->reduced_value;
 					named = true;
 				} else {
 					// Regular indexing.