SrcSpan

tst/Compiler/TypesSpec.hs

@@ -0,0 +1,67 @@
+{-# LANGUAGE ParallelListComp #-}
+module Compiler.TypesSpec
+    ( spec
+    )
+    where
+--------------------------------------------------------------------------------
+import Control.Lens.Combinators
+import Data.Function            ((&))
+
+import Test.QuickCheck
+import Test.Hspec
+
+import Compiler.Types           (SrcSpan(..), srcSpanAbs, srcSpanLen)
+--------------------------------------------------------------------------------
+
+spec :: Spec
+spec = do
+    describe "SrcSpan" $ do
+        -- it "associates under closure"
+        --     prop_SrcSpan_mul_associative
+        it "commutes under closure"
+            prop_SrcSpan_mul_commutative
+        it "equals itself when squared"
+            prop_SrcSpan_mul_square_eq
+
+prop_SrcSpan_mul_associative :: Property
+prop_SrcSpan_mul_associative = property $ \a b c ->
+    -- very crudely approximate when overflow will occur; bail we think it
+    -- will
+    (([a,b,c] :: [SrcSpan]) & allOf (each . (srcSpanAbs <> srcSpanLen))
+                                    (< (maxBound @Int `div` 3)))
+    ==> (a <> b) <> c === a <> (b <> c :: SrcSpan)
+
+prop_SrcSpan_mul_commutative :: Property
+prop_SrcSpan_mul_commutative = property $ \a b ->
+    a <> b === (b <> a :: SrcSpan)
+
+prop_SrcSpan_mul_square_eq :: Property
+prop_SrcSpan_mul_square_eq = property $ \a ->
+    a <> a === (a :: SrcSpan)
+
+instance Arbitrary SrcSpan where
+    arbitrary = do
+        l <- chooseInt (1, maxBound)
+        c <- chooseInt (1, maxBound)
+        a <- chooseInt (0, maxBound)
+            `suchThat` (\n -> n >= pred l + pred c)
+        s <- chooseInt (0, maxBound)
+        pure $ SrcSpan l c a s
+
+    shrink (SrcSpan l c a s) =
+        [ SrcSpan l' c' a' s'
+        | (l',c',a',s') <- shrinkParts
+        , l' >= 1
+        , c' >= 1
+        , a' >= pred l' + pred c'
+        ]
+      where
+        -- shfl as = unsafePerformIO (generate $ shuffle as)
+        shrinkParts = 
+            [ (l',c',a',s')
+            | l' <- shrinkIntegral l
+            | c' <- shrinkIntegral c
+            | a' <- shrinkIntegral a
+            | s' <- shrinkIntegral s
+            ]
+