Fix Issue 508 (#511)

Fix Issue 508
merged-on-behalf-of: Brian Schott <Hackerpilot@users.noreply.github.com>

src/dfmt/formatter.d

@@ -9,8 +9,8 @@ module dfmt.formatter;
 import dparse.lexer;
 import dparse.parser;
 import dparse.rollback_allocator;
-import dfmt.config;
 import dfmt.ast_info;
+import dfmt.config;
 import dfmt.indentation;
 import dfmt.tokens;
 import dfmt.wrapping;
@@ -765,6 +765,7 @@ private:
         }
         else if (hasCurrent && (currentIs(tok!"@")
                 || isBasicType(tokens[index].type)
+                || currentIs(tok!"invariant")
                 || currentIs(tok!"extern")
                 || currentIs(tok!"identifier"))
                 && !currentIsIndentedTemplateConstraint())

tests/allman/issue0508.d.ref

@@ -0,0 +1,7 @@
+struct S
+{
+    @safe invariant
+    {
+        assert(true);
+    }
+}

tests/issue0508.d

@@ -0,0 +1 @@
+struct S {@safe invariant { assert(true); }}

tests/otbs/issue0508.d.ref

@@ -0,0 +1,5 @@
+struct S {
+    @safe invariant {
+        assert(true);
+    }
+}