Add ContExpression syntax tree.

This is for expressions which must be calculatable at compile time.

1 files changed, 19 insertions, 3 deletions

diff --git a/src/Language/Fiddle/Ast/Internal/SyntaxTree.hs b/src/Language/Fiddle/Ast/Internal/SyntaxTree.hs
index 5a8aa6d..613dae4 100644
--- a/src/Language/Fiddle/Ast/Internal/SyntaxTree.hs
+++ b/src/Language/Fiddle/Ast/Internal/SyntaxTree.hs
@@ -30,6 +30,7 @@ module Language.Fiddle.Ast.Internal.SyntaxTree
     FiddleUnit (..),
     Identifier (..),
     Expression (..),
+    ConstExpression (..),
     ImportStatement (..),
     ImportList (..),
     FiddleDecl (..),
@@ -53,6 +54,7 @@ module Language.Fiddle.Ast.Internal.SyntaxTree
     mapDirectedM,
     asDirected,
     undirected,
+    trueValue,
   )
 where
 
@@ -284,6 +286,20 @@ data Identifier f a = Identifier
   }
   deriving (Generic, Annotated, Alter, Typeable, Walk)
 
+-- | Const expressions are expressions which must be eventually calculated
+-- during compilation. This means all the data required to fully calculate the
+-- expression must exist at compile time.
+data ConstExpression u (s :: Stage) :: SynTree where
+  ConstExpression ::
+    { constExpression :: Variant (s .>= Qualified) (N u) (Expression u s f a),
+      constExpressionAnnot :: a
+    } ->
+    ConstExpression u s f a
+  deriving (Generic, Annotated, Alter, Typeable, Walk)
+
+trueValue :: (s .>= Qualified ~ True) => ConstExpression u s f a -> N u
+trueValue (ConstExpression {constExpression = (LeftV v)}) = v
+
 -- | Expressions used within Fiddle, including literals and variables.
 data Expression (u :: unit) (s :: Stage) :: SynTree where
   -- | A numeric literal, whose value is dependent on the compilation stage.
@@ -385,7 +401,7 @@ data FiddleDecl :: StagedSynTree where
       -- | The location identifier.
       locationIdent :: Identifier f a,
       -- | The associated expression.
-      locationExpr :: Expression Address stage f a,
+      locationExpr :: ConstExpression Address stage f a,
       -- | Annotation for the location declaration.
       locationAnnot :: a
     } ->
@@ -462,7 +478,7 @@ data ObjType stage f a where
     { -- | The type of the array elements.
       arrayObjType :: ObjType stage f a,
       -- | The size of the array.
-      arraySize :: Expression Unitless stage f a,
+      arraySize :: ConstExpression Unitless stage f a,
       -- | Annotation for the array type.
       arrayAnnot :: a
     } ->
@@ -632,7 +648,7 @@ data RegisterBitsTypeRef stage f a where
     { -- | Reference to the array type.
       bitsArrayTypeRef :: RegisterBitsTypeRef stage f a,
       -- | Size of the array.
-      bitsArraySize :: Expression Unitless stage f a,
+      bitsArraySize :: ConstExpression Unitless stage f a,
       -- | Annotation for the array.
       bitsArrayAnnot :: a
     } ->