From 2abfe8c0a6054a3cfd427e36204e17ceae71ccaa Mon Sep 17 00:00:00 2001
From: Denis Buzdalov <public@buzden.ru>
Date: Mon, 18 Jul 2022 13:17:00 +0300
Subject: [PATCH] [ fix ] Fix the order of search, look for already derived
 before hinted

---
 src/Deriving/DepTyCheck/Gen/Checked.idr | 32 ++++++++++++-------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/src/Deriving/DepTyCheck/Gen/Checked.idr b/src/Deriving/DepTyCheck/Gen/Checked.idr
index 09be141be..4255b0511 100644
--- a/src/Deriving/DepTyCheck/Gen/Checked.idr
+++ b/src/Deriving/DepTyCheck/Gen/Checked.idr
@@ -110,37 +110,35 @@ namespace ClojuringCanonicImpl
   DerivatorCore => ClojuringContext m => Elaboration m => CanonicGen m where
     callGen sig fuel values = do
 
+      --- check if no derivation is needed ---
+
       -- look for external gens, and call it if exists
       let Nothing = lookupLengthChecked sig !ask
         | Just (name, Element extSig lenEq) => pure $ callExternalGen extSig name (var outmostFuelArg) $ rewrite lenEq in values
 
+      -- look for existing already derived (internal) gen, use it if exists
+      let Nothing = lookup sig !get
+        | Just internalGenName => pure $ callCanonic sig internalGenName fuel values
+
       -- look for very external gens, i.e. those that can be reached with `%search`
       canonicSigType <- try .| check (canonicSig sig)
                             .| fail "INTERNAL ERROR: canonic signature of \{show sig.targetType.name} is not a type"
       Nothing <- search canonicSigType
         | Just found => flip (foldl app) values <$> flip app fuel <$> quote found
 
-      -- get the name of internal gen, derive if necessary
-      internalGenName <- do
-
-        -- look for existing (already derived) internals, use it if exists
-        let Nothing = lookup sig !get
-          | Just name => pure name
-
-        -- nothing found, then derive! acquire the name
-        let name = nameForGen sig
+      --- nothing's found, then derive! ---
 
-        -- remember that we're responsible for this signature derivation
-        modify $ insert sig name
+      -- acquire the name
+      let internalGenName = nameForGen sig
 
-        -- derive declaration and body for the asked signature. It's important to call it AFTER update of the map in the state to not to cycle
-        (genFunClaim, genFunBody) <- logBounds "type" [sig] $ assert_total $ deriveCanonical sig name
+      -- remember that we're responsible for this signature derivation
+      modify $ insert sig internalGenName
 
-        -- remember the derived stuff
-        tell ([genFunClaim], [genFunBody])
+      -- derive declaration and body for the asked signature. It's important to call it AFTER update of the map in the state to not to cycle
+      (genFunClaim, genFunBody) <- logBounds "type" [sig] $ assert_total $ deriveCanonical sig internalGenName
 
-        -- return the name of the newly derived generator
-        pure name
+      -- remember the derived stuff
+      tell ([genFunClaim], [genFunBody])
 
       -- call the internal gen
       pure $ callCanonic sig internalGenName fuel values