Don't modify the module cache after elaboration failures

6 files changed, 21 insertions, 0 deletions

diff --git a/src/elaborate.sml b/src/elaborate.sml
index 26ec21ec..41e9e9ab 100644
--- a/src/elaborate.sml
+++ b/src/elaborate.sml
@@ -4461,6 +4461,8 @@ fun resolveClass env = E.resolveClass (hnormCon env) (consEq env dummy) env
 
 fun elabFile basis basis_tm topStr topSgn top_tm env file =
     let
+        val () = ModDb.snapshot ()
+
         val () = mayDelay := true
         val () = delayedUnifs := []
         val () = delayedExhaustives := []
@@ -4788,6 +4790,11 @@ fun elabFile basis basis_tm topStr topSgn top_tm env file =
             end
         else
             ();
+
+        if ErrorMsg.anyErrors () then
+            ModDb.revert ()
+        else
+            ();
         
         (L'.DFfiStr ("Basis", basis_n, sgn), ErrorMsg.dummySpan)
         :: ds
diff --git a/src/mod_db.sig b/src/mod_db.sig
index 2b98ae6f..8f78f2c2 100644
--- a/src/mod_db.sig
+++ b/src/mod_db.sig
@@ -35,4 +35,8 @@ signature MOD_DB = sig
      * We might invalidate other declarations that depend on this one, if the timestamp has changed. *)
 
     val lookup : Source.decl -> Elab.decl option
+
+    (* Allow undoing to snapshots after failed compilations. *)
+    val snapshot : unit -> unit
+    val revert : unit -> unit
 end
diff --git a/src/mod_db.sml b/src/mod_db.sml
index 22c11183..5e9e3342 100644
--- a/src/mod_db.sml
+++ b/src/mod_db.sml
@@ -141,4 +141,10 @@ fun lookup (d : Source.decl) =
                  NONE)
       | _ => NONE
 
+val byNameBackup = ref (!byName)
+val byIdBackup = ref (!byId)
+
+fun snapshot () = (byNameBackup := !byName; byIdBackup := !byId)
+fun revert () = (byName := !byNameBackup; byId := !byIdBackup)
+
 end
diff --git a/tests/baddep.urp b/tests/baddep.urp
new file mode 100644
index 00000000..0e65b25d
--- /dev/null
+++ b/tests/baddep.urp
@@ -0,0 +1,2 @@
+baddep1
+baddep2
diff --git a/tests/baddep1.ur b/tests/baddep1.ur
new file mode 100644
index 00000000..14573638
--- /dev/null
+++ b/tests/baddep1.ur
@@ -0,0 +1 @@
+val x : int = "hi"
diff --git a/tests/baddep2.ur b/tests/baddep2.ur
new file mode 100644
index 00000000..22c5e3ae
--- /dev/null
+++ b/tests/baddep2.ur
@@ -0,0 +1 @@
+fun main () : transaction page = return <xml/>