Fix Dart doc (#398)

tool/templates/dart/base.dart.jinja

@@ -5,13 +5,10 @@
 
 {% for directive in directives -%}
 {{directive}}
-{% endfor -%}
-
+{% endfor %}
 {{ body }}
-
-{%- for helper_class in helper_classes.values() %}
-
+{% for helper_class in helper_classes.values() -%}
+{%- if !loop.first %}
+{% endif -%}
 {{helper_class}}
-
-{%- endfor %}
-
+{% endfor -%}

tool/templates/dart/enum.dart.jinja

@@ -1,6 +1,6 @@
-{%- if !docs.is_empty() %}
+{% if !docs.is_empty() -%}
 /// {{docs}}
-{%- endif %}
+{% endif -%}
 enum {{type_name}} {
 {%- for enum_variant in ty.variants %}
   {% if !enum_variant.docs.is_empty() -%}

tool/templates/dart/init.dart

@@ -1,4 +1,3 @@
-
 /// A [Rune] is a Unicode code point, such as `a`, or `💡`.
 /// 
 /// The recommended way to obtain a [Rune] is to create it from a 

tool/templates/dart/opaque.dart.jinja

@@ -1,6 +1,6 @@
-{%- if !docs.is_empty() %}
+{% if !docs.is_empty() -%}
 /// {{docs}}
-{%- endif %}
+{% endif -%}
 final class {{type_name}} implements ffi.Finalizable {
   final ffi.Pointer<ffi.Opaque> _underlying;
 

tool/templates/dart/struct.dart.jinja

@@ -1,6 +1,3 @@
-{%- if !docs.is_empty() %}
-/// {{docs}}
-{%- endif %}
 final class _{{type_name}}Ffi extends ffi.Struct {
   {%- for field in fields %}
   {%- match field.annotation %}
@@ -12,6 +9,9 @@ final class _{{type_name}}Ffi extends ffi.Struct {
   {%- endfor %}
 }
 
+{% if !docs.is_empty() -%}
+/// {{docs}}
+{% endif -%}
 final class {{type_name}} {
   final _{{type_name}}Ffi _underlying;