Struct is shorthand syntax

lib/AST.hs

@@ -38,7 +38,7 @@ data Expr
     | Discard Expr
     | Import {objects :: [String], from :: String, qualified :: Bool, as :: Maybe String}
     | Ref Expr
-    | Struct {name :: String, fields :: [(String, Type)], refinement :: Maybe Expr, refinementSrc :: String}
+    | Struct {name :: String, fields :: [(String, Type)], refinement :: Maybe Expr, refinementSrc :: String, is :: [String]}
     | StructLit String [(String, Expr)] Position
     | StructAccess Expr Expr
     | ListLit [Expr]

lib/BytecodeCompiler.hs

@@ -432,9 +432,10 @@ compileExpr (Parser.Cast from to) = do
     compileType (Parser.Var "CPtr" _) = [Push $ DCPtr $ ptrToWordPtr nullPtr]
     compileType (Parser.ListLit [x]) = compileType x ++ [PackList 1]
     compileType x = error $ "Type " ++ show x ++ " is not implemented"
-compileExpr st@(Parser.Struct{fields}) = do
+compileExpr st@(Parser.Struct{name = structName, fields, is}) = do
     modify (\s -> s{structDecs = st : structDecs s})
     mapM_ createFieldTrait fields
+    mapM_ (compileExpr . (\t -> Parser.Impl{methods = [], for = structName, trait = t})) is
     return []
   where
     createFieldTrait :: (String, Parser.Type) -> StateT (CompilerState a) IO ()

lib/Parser.hs

@@ -359,7 +359,10 @@ struct = do
     refinement <- optional $ do
         keyword "satisfies"
         parens expr
-    return $ Struct{name = name, fields = fields, refinement = refinement, refinementSrc = fromMaybe "" refinementSrc}
+    is <- optional $ do
+        keyword "is"
+        sepBy extra (symbol ",")
+    return $ Struct{name = name, fields = fields, refinement = refinement, refinementSrc = fromMaybe "" refinementSrc, is = fromMaybe [] is}
   where
     structField = do
         fieldName <- identifier <?> "field name"

tests/IntegrationSpec.hs

@@ -189,6 +189,14 @@ spec = do
                     println name mauzi
                 end|]
                 `shouldReturn` "Mauzi\n"
+        it "Can use `is` syntax" $ do
+            compileAndRun
+                [r|
+                trait Person
+                trait Human
+                struct Person = (name: String, age: Int) is Person, Human
+                |]
+                `shouldReturn` ""
     describe "Traits" $ do
         it "Can use a trait" $ do
             compileAndRun

tests/ParserSpec.hs

@@ -59,6 +59,15 @@ spec = do
             parseProgram "bello{}.name" parserCompilerFlags
                 `shouldBe` Right
                     (Program [StructAccess (StructLit "bello" [] anyPosition) (Var "name" anyPosition)])
+        it "Can define" $
+            parseProgram "struct Teacher = ()" parserCompilerFlags
+                `shouldBe` Right (Program [Struct{name = "Teacher", fields = [], refinement = Nothing, refinementSrc = "", is = []}])
+        it "Can define with is" $ do
+            parseProgram "struct Teacher = () is Person" parserCompilerFlags
+                `shouldBe` Right (Program [Struct{name = "Teacher", fields = [], refinement = Nothing, refinementSrc = "", is = ["Person"]}])
+        it "Can define with multiple is" $ do
+            parseProgram "struct Teacher = () is Person, Employee" parserCompilerFlags
+                `shouldBe` Right (Program [Struct{name = "Teacher", fields = [], refinement = Nothing, refinementSrc = "", is = ["Person", "Employee"]}])
     describe "Traits" $ do
         it "Should parse a trait decleration" $
             parseProgram "trait Show = do\nshow :: Self -> String\nend" parserCompilerFlags