Add <using> annotation to export enum fields

nelua/analyzer.lua

@@ -440,6 +440,23 @@ function visitors.Annotation(context, node, symbol)
     end
   elseif name == 'codename' then
     objattr.fixedcodename = params
+  elseif name == 'using' then
+    assert(objattr._type)
+    if not objattr.is_enum then
+      node:raisef("annotation 'using' can only be used with enums")
+    end
+    -- inject all enum fields as comptime values
+    for _,field in ipairs(objattr.fields) do
+      local fieldsymbol = Symbol{
+        name = field.name,
+        codename = objattr.codename..'_'..field.name,
+        comptime = true,
+        type = objattr,
+        value = field.value,
+        scope = symbol.scope,
+      }
+      symbol.scope:add_symbol(fieldsymbol)
+    end
   end
 
   node.done = true

nelua/typedefs.lua

@@ -265,6 +265,8 @@ typedefs.type_annots = {
   -- Mark a record type for forward declaration.
   -- This allows to use pointers to a record before defining it.
   forwarddecl = true,
+  -- Whether to use enum fields in the declared scope.
+  using = true,
 }
 
 return typedefs

spec/03-typechecker_spec.lua

@@ -1754,4 +1754,17 @@ it("forward type declaration", function()
     "cannot be of forward declared type")
 end)
 
+it("using annotation", function()
+  assert.analyze_ast([[
+    local MyEnum <using> = @enum{
+      MYENUM_NONE = 0,
+      MYENUM_ONE = 1,
+    }
+    local a: MyEnum = MYENUM_ONE
+  ]])
+  assert.analyze_error([[
+    local MyEnum <using> = @record{}
+  ]], "annotation 'using' can only")
+end)
+
 end)