add let to the core

lib/Quox/Untyped/Erase.idr

@@ -222,6 +222,25 @@ eraseTerm ctx ty (Box val loc) = do
     Erased => pure $ Erased loc
     Kept   => eraseTerm ctx a val
 
+--         s ⤋ s' ⇐ A
+-- ----------------------------
+--   let0 x = e in s ⤋ s' ⇐ A
+--
+--     e ⤋ e'  s ⤋ s' ⇐ A   π ≠ 0
+-- -------------------------------------
+--  letπ x = e in s ⤋ let x = e' in s'
+eraseTerm ctx ty (Let pi e s loc) = do
+  let x = s.name
+  case isErased pi of
+    Erased => do
+      ety <- computeElimType ctx SZero e
+      s'  <- eraseTerm (extendTy pi x ety ctx) (weakT 1 ty) s.term
+      pure $ sub1 (Erased e.loc) s'
+    Kept => do
+      EraRes ety e' <- eraseElim ctx e
+      s' <- eraseTerm (extendTy pi x ety ctx) (weakT 1 ty) s.term
+      pure $ Let x e' s' loc
+
 --  e ⤋ e' ⇒ B
 -- ------------
 --  e ⤋ e' ⇐ A

lib/Quox/Untyped/Syntax.idr

@@ -96,11 +96,6 @@ public export
 Definitions = SortedMap Name Definition
 
 
-export
-letD, inD : {opts : LayoutOpts} -> Eff Pretty (Doc opts)
-letD = hl Syntax "let"
-inD  = hl Syntax "in"
-
 export covering
 prettyTerm : {opts : LayoutOpts} -> BContext n ->
              Term n -> Eff Pretty (Doc opts)