copilot-theorem: Add Show and ShowF instances for counterexamples. Refs Copilot-Language#589.

RyanGlScott · RyanGlScott · commit 2e7622e569cd · 2025-02-24T17:26:44.000-05:00
Currently, the `Copilot.Theorem.What4.prove` function returns a list of
results, where each result contains a `SatResult` that describes whether a
property is `Valid`, `Invalid`, or `Unknown`. The `Invalid` result has the
limitation that it does not give any information about a specific
counterexample that could drive Copilot into falsifying the property, however.
This makes it challenging to interpret what the results of prove mean.

The `CounterExample`, `SatResultCex`, and `CopilotValue` data types lack `Show`
and `ShowF` instances, which makes it impractical for users to display them.

This commit adds `Show` and `ShowF` instances for all three data types so that
they can be shown.
diff --git a/copilot-theorem/src/Copilot/Theorem/What4.hs b/copilot-theorem/src/Copilot/Theorem/What4.hs
@@ -69,6 +69,7 @@ import qualified Data.BitVector.Sized as BV
 import Data.Foldable (foldrM)
 import Data.List (genericLength)
 import qualified Data.Map as Map
+import Data.Parameterized.Classes (ShowF)
 import Data.Parameterized.NatRepr
 import Data.Parameterized.Nonce
 import Data.Parameterized.Some
@@ -100,6 +101,7 @@ data SatResult = Valid | Invalid | Unknown
 -- each property in a spec. This is largely the same as 'SatResult', except that
 -- 'InvalidCex' also records a 'CounterExample'.
 data SatResultCex = ValidCex | InvalidCex CounterExample | UnknownCex
+  deriving Show
 
 -- | Concrete values that cause a property in a Copilot specification to be
 -- invalid. As a simple example, consider the following spec:
@@ -250,6 +252,7 @@ data CounterExample = CounterExample
     -- is the concrete value of the extern stream at that time step.
   , concreteStreamValues :: Map.Map (CE.Id, StreamOffset) (Some CopilotValue)
   }
+  deriving Show
 
 -- | Attempt to prove all of the properties in a spec via an SMT solver (which
 -- must be installed locally on the host). Return an association list mapping
@@ -625,6 +628,24 @@ expectedBool what xe =
 data CopilotValue a where
   CopilotValue :: CT.Typed a => CT.Type a -> a -> CopilotValue a
 
+instance Show (CopilotValue a) where
+  showsPrec p (CopilotValue ty val) =
+    case ty of
+      CT.Bool -> showsPrec p val
+      CT.Int8 -> showsPrec p val
+      CT.Int16 -> showsPrec p val
+      CT.Int32 -> showsPrec p val
+      CT.Int64 -> showsPrec p val
+      CT.Word8 -> showsPrec p val
+      CT.Word16 -> showsPrec p val
+      CT.Word32 -> showsPrec p val
+      CT.Word64 -> showsPrec p val
+      CT.Float -> showsPrec p val
+      CT.Double -> showsPrec p val
+      CT.Array {} -> showsPrec p val
+      CT.Struct {} -> showsPrec p val
+instance ShowF CopilotValue
+
 -- | Convert a symbolic 'XExpr' into a concrete 'CopilotValue'. Note that
 -- struct values are not currently supported, so attempting to convert an
 -- 'XStruct' fail will raise an error.
