Fixing support for argument scopes and let-ins while interning cases patterns.

We also simplify the whole process of interpretation of cases pattern
on the way.

2 files changed, 16 insertions, 12 deletions

diff --git a/pretyping/cases.ml b/pretyping/cases.ml
index a793e217d4..14417d15c6 100644
--- a/pretyping/cases.ml
+++ b/pretyping/cases.ml
@@ -46,8 +46,8 @@ module NamedDecl = Context.Named.Declaration
 type pattern_matching_error =
   | BadPattern of constructor * constr
   | BadConstructor of constructor * inductive
-  | WrongNumargConstructor of constructor * int
-  | WrongNumargInductive of inductive * int
+  | WrongNumargConstructor of constructor * bool * int * int * int
+  | WrongNumargInductive of inductive * bool * int * int * int
   | UnusedClause of cases_pattern list
   | NonExhaustive of cases_pattern list
   | CannotInferPredicate of (constr * types) array
@@ -65,11 +65,11 @@ let error_bad_constructor ?loc env cstr ind =
   raise_pattern_matching_error ?loc
     (env, Evd.empty, BadConstructor (cstr,ind))
 
-let error_wrong_numarg_constructor ?loc env c n =
-  raise_pattern_matching_error ?loc (env, Evd.empty, WrongNumargConstructor(c,n))
+let error_wrong_numarg_constructor ?loc env c expanded n n1 n2 =
+  raise_pattern_matching_error ?loc (env, Evd.empty, WrongNumargConstructor(c,expanded,n,n1,n2))
 
-let error_wrong_numarg_inductive ?loc env c n =
-  raise_pattern_matching_error ?loc (env, Evd.empty, WrongNumargInductive(c,n))
+let error_wrong_numarg_inductive ?loc env c expanded n n1 n2 =
+  raise_pattern_matching_error ?loc (env, Evd.empty, WrongNumargInductive(c,expanded,n,n1,n2))
 
 let list_try_compile f l =
   let rec aux errors = function
@@ -519,13 +519,17 @@ let check_and_adjust_constructor env ind cstrs pat = match DAst.get pat with
         (* Check the constructor has the right number of args *)
         let ci = cstrs.(i-1) in
         let nb_args_constr = ci.cs_nargs in
-        if Int.equal (List.length args) nb_args_constr then pat
+        let nargs = List.length args in
+        if Int.equal nargs nb_args_constr then pat
         else
           try
             let args' = adjust_local_defs ?loc (args, List.rev ci.cs_args)
             in DAst.make ?loc @@ PatCstr (cstr, args', alias)
           with NotAdjustable ->
-            error_wrong_numarg_constructor ?loc env cstr nb_args_constr
+            let nlet = List.count (function LocalDef _ -> true | _ -> false) ci.cs_args in
+            (* In practice, this is already checked at interning *)
+            error_wrong_numarg_constructor ?loc env cstr
+              (* as if not expanded: *) false nargs nb_args_constr (nb_args_constr + nlet)
       else
         (* Try to insert a coercion *)
         try
diff --git a/pretyping/cases.mli b/pretyping/cases.mli
index 9a986bc14c..10fd085e3a 100644
--- a/pretyping/cases.mli
+++ b/pretyping/cases.mli
@@ -23,17 +23,17 @@ open Evardefine
 type pattern_matching_error =
   | BadPattern of constructor * constr
   | BadConstructor of constructor * inductive
-  | WrongNumargConstructor of constructor * int
-  | WrongNumargInductive of inductive * int
+  | WrongNumargConstructor of constructor * bool * int * int * int
+  | WrongNumargInductive of inductive * bool * int * int * int
   | UnusedClause of cases_pattern list
   | NonExhaustive of cases_pattern list
   | CannotInferPredicate of (constr * types) array
 
 exception PatternMatchingError of env * evar_map * pattern_matching_error
 
-val error_wrong_numarg_constructor : ?loc:Loc.t -> env -> constructor -> int -> 'a
+val error_wrong_numarg_constructor : ?loc:Loc.t -> env -> constructor -> bool -> int -> int -> int -> 'a
 
-val error_wrong_numarg_inductive   : ?loc:Loc.t -> env -> inductive -> int -> 'a
+val error_wrong_numarg_inductive   : ?loc:Loc.t -> env -> inductive -> bool -> int -> int -> int -> 'a
 
 val irrefutable : env -> cases_pattern -> bool