Add well-formedness check for type schemes in valspecs.

Fixes #47.
Also adjust the nexp substitution so that the error message points to a
useful location, and replace the empty environment with the initial
environment in a few functions that do type checking to ensure that the
prover is set up (which may be needed for the wf check).

14 files changed, 61 insertions, 22 deletions

diff --git a/src/ast_util.ml b/src/ast_util.ml
index 7a42950c..1f550c73 100644
--- a/src/ast_util.ml
+++ b/src/ast_util.ml
@@ -1855,7 +1855,13 @@ let order_subst_aux sv subst = function
 
 let order_subst sv subst (Ord_aux (ord, l)) = Ord_aux (order_subst_aux sv subst ord, l)
 
-let rec nexp_subst sv subst (Nexp_aux (nexp, l)) = Nexp_aux (nexp_subst_aux sv subst nexp, l)
+let rec nexp_subst sv subst = function
+  | (Nexp_aux (Nexp_var kid, l)) as nexp ->
+     begin match subst with
+     | A_aux (A_nexp n, _) when Kid.compare kid sv = 0 -> n
+     | _ -> nexp
+     end
+  | Nexp_aux (nexp, l) -> Nexp_aux (nexp_subst_aux sv subst nexp, l)
 and nexp_subst_aux sv subst = function
   | Nexp_var kid ->
      begin match subst with
diff --git a/src/monomorphise.ml b/src/monomorphise.ml
index 93579420..8670139f 100644
--- a/src/monomorphise.ml
+++ b/src/monomorphise.ml
@@ -3439,7 +3439,7 @@ let add_bitvector_casts (Defs defs) =
       mk_val_spec (VS_val_spec (ts,name,[("_", "zeroExtend")],false))
     in
     let defs = List.map mkfn (IdSet.elements !specs_required) in
-    check Env.empty (Defs defs)
+    check initial_env (Defs defs)
   in Defs (cast_specs @ defs)
 end
 
diff --git a/src/rewrites.ml b/src/rewrites.ml
index 4ea52c4d..e3864a7f 100644
--- a/src/rewrites.ml
+++ b/src/rewrites.ml
@@ -1440,7 +1440,7 @@ let rewrite_defs_exp_lift_assign env defs = rewrite_defs_base
      write_reg_ref (vector_access (GPR, i)) exp
  *)
 let rewrite_register_ref_writes (Defs defs) =
-  let (Defs write_reg_spec) = fst (Type_error.check Env.empty (Defs (List.map gen_vs
+  let (Defs write_reg_spec) = fst (Type_error.check initial_env (Defs (List.map gen_vs
     [("write_reg_ref", "forall ('a : Type). (register('a), 'a) -> unit effect {wreg}")]))) in
   let lexp_ref_exp (LEXP_aux (_, annot) as lexp) =
     try
@@ -1630,7 +1630,7 @@ let rewrite_defs_early_return env (Defs defs) =
     FD_aux (FD_function (rec_opt, tannot_opt, effect_opt,
       List.map (rewrite_funcl_early_return rewriters) funcls), a) in
 
-  let (Defs early_ret_spec) = fst (Type_error.check Env.empty (Defs [gen_vs
+  let (Defs early_ret_spec) = fst (Type_error.check initial_env (Defs [gen_vs
     ("early_return", "forall ('a : Type) ('b : Type). 'a -> 'b effect {escape}")])) in
 
   rewrite_defs_base
@@ -3771,7 +3771,7 @@ let rewrite_defs_remove_superfluous_returns env =
 
 
 let rewrite_defs_remove_e_assign env (Defs defs) =
-  let (Defs loop_specs) = fst (Type_error.check Env.empty (Defs (List.map gen_vs
+  let (Defs loop_specs) = fst (Type_error.check initial_env (Defs (List.map gen_vs
     [("foreach#", "forall ('vars : Type). (int, int, int, bool, 'vars, 'vars) -> 'vars");
      ("while#", "forall ('vars : Type). (bool, 'vars, 'vars) -> 'vars");
      ("until#", "forall ('vars : Type). (bool, 'vars, 'vars) -> 'vars");
diff --git a/src/type_check.ml b/src/type_check.ml
index 9c37f5c9..02e32f4d 100644
--- a/src/type_check.ml
+++ b/src/type_check.ml
@@ -825,10 +825,11 @@ end = struct
     | A_typ typ -> wf_typ ~exs:exs env typ
     | A_order ord -> wf_order env ord
     | A_bool nc -> wf_constraint ~exs:exs env nc
-  and wf_nexp ?exs:(exs=KidSet.empty) env (Nexp_aux (nexp_aux, l) as nexp) =
+  and wf_nexp ?exs:(exs=KidSet.empty) env nexp =
     wf_debug "nexp" string_of_nexp nexp exs;
+    let Nexp_aux (nexp_aux, l) = expand_nexp_synonyms env nexp in
     match nexp_aux with
-    | Nexp_id _ -> ()
+    | Nexp_id id -> typ_error env l ("Undefined synonym " ^ string_of_id id)
     | Nexp_var kid when KidSet.mem kid exs -> ()
     | Nexp_var kid ->
        begin match get_typ_var kid env with
@@ -1324,6 +1325,10 @@ let add_typquant l (quant : typquant) (env : Env.t) : Env.t =
 let expand_bind_synonyms l env (typq, typ) =
   typq, Env.expand_synonyms (add_typquant l typq env) typ
 
+let wf_typschm env (TypSchm_aux (TypSchm_ts (typq, typ), l)) =
+  let env = add_typquant l typq env in
+  Env.wf_typ env typ
+
 (* Create vectors with the default order from the environment *)
 
 let default_order_error_string =
@@ -4899,6 +4904,7 @@ let check_val_spec env (VS_aux (vs, (l, _))) =
   let vs, id, typq, typ, env = match vs with
     | VS_val_spec (TypSchm_aux (TypSchm_ts (typq, typ), ts_l) as typschm, id, exts, is_cast) ->
        typ_print (lazy (Util.("Check val spec " |> cyan |> clear) ^ string_of_id id ^ " : " ^ string_of_typschm typschm));
+       wf_typschm env typschm;
        let env = Env.add_extern id exts env in
        let env = if is_cast then Env.add_cast id env else env in
        let typq', typ' = expand_bind_synonyms ts_l env (typq, typ) in
diff --git a/test/typecheck/pass/Replicate/v2.expect b/test/typecheck/pass/Replicate/v2.expect
index acadd4e2..89ab2910 100644
--- a/test/typecheck/pass/Replicate/v2.expect
+++ b/test/typecheck/pass/Replicate/v2.expect
@@ -2,7 +2,7 @@ Type error:
 [Replicate/v2.sail]:13:4-30
 13 |    replicate_bits(x, 'N / 'M)
    |    ^------------------------^
-   | Tried performing type coercion from {('ex119# : Int), true. vector(('M * 'ex119#), dec, bit)} to vector('N, dec, bit) on replicate_bits(x, tdiv_int(__id(N), bitvector_length(x)))
+   | Tried performing type coercion from {('ex172# : Int), true. vector(('M * 'ex172#), dec, bit)} to vector('N, dec, bit) on replicate_bits(x, tdiv_int(__id(N), bitvector_length(x)))
    | Coercion failed because:
    | Mismatched argument types in subtype check
    | 
diff --git a/test/typecheck/pass/existential_ast/v3.expect b/test/typecheck/pass/existential_ast/v3.expect
index 7bb8a4ab..56b89364 100644
--- a/test/typecheck/pass/existential_ast/v3.expect
+++ b/test/typecheck/pass/existential_ast/v3.expect
@@ -3,5 +3,5 @@ Type error:
 26 |  Some(Ctor1(a, x, c))
    |       ^------------^
    | Could not resolve quantifiers for Ctor1
-   | * datasize('ex196#)
+   | * datasize('ex248#)
    | 
diff --git a/test/typecheck/pass/existential_ast3/v1.expect b/test/typecheck/pass/existential_ast3/v1.expect
index 4b9bd7cc..346b7b75 100644
--- a/test/typecheck/pass/existential_ast3/v1.expect
+++ b/test/typecheck/pass/existential_ast3/v1.expect
@@ -4,17 +4,17 @@ Type error:
    |                                                ^---------------^
    | Tried performing type coercion from (int(33), range(0, (2 ^ 5 - 1))) to {('d : Int) ('n : Int), (datasize('d) & (0 <= 'n & ('n + 1) <= 'd)). (int('d), int('n))} on (33, unsigned(a))
    | Coercion failed because:
-   | (int(33), int('ex158#)) is not a subtype of (int('ex153#), int('ex154#))
+   | (int(33), int('ex210#)) is not a subtype of (int('ex205#), int('ex206#))
    | [existential_ast3/v1.sail]:17:48-65
    | 17 |    if b == 0b0 then (64, unsigned(b @ a)) else (33, unsigned(a));
    |    |                                                ^---------------^
-   |    | 'ex153# bound here
+   |    | 'ex205# bound here
    | [existential_ast3/v1.sail]:17:48-65
    | 17 |    if b == 0b0 then (64, unsigned(b @ a)) else (33, unsigned(a));
    |    |                                                ^---------------^
-   |    | 'ex154# bound here
+   |    | 'ex206# bound here
    | [existential_ast3/v1.sail]:17:48-65
    | 17 |    if b == 0b0 then (64, unsigned(b @ a)) else (33, unsigned(a));
    |    |                                                ^---------------^
-   |    | 'ex158# bound here
+   |    | 'ex210# bound here
    | 
diff --git a/test/typecheck/pass/existential_ast3/v2.expect b/test/typecheck/pass/existential_ast3/v2.expect
index 52eb2f13..7f18c94e 100644
--- a/test/typecheck/pass/existential_ast3/v2.expect
+++ b/test/typecheck/pass/existential_ast3/v2.expect
@@ -4,17 +4,17 @@ Type error:
    |                                                ^---------------^
    | Tried performing type coercion from (int(31), range(0, (2 ^ 5 - 1))) to {('d : Int) ('n : Int), (datasize('d) & (0 <= 'n & ('n + 1) <= 'd)). (int('d), int('n))} on (31, unsigned(a))
    | Coercion failed because:
-   | (int(31), int('ex158#)) is not a subtype of (int('ex153#), int('ex154#))
+   | (int(31), int('ex210#)) is not a subtype of (int('ex205#), int('ex206#))
    | [existential_ast3/v2.sail]:17:48-65
    | 17 |    if b == 0b0 then (64, unsigned(b @ a)) else (31, unsigned(a));
    |    |                                                ^---------------^
-   |    | 'ex153# bound here
+   |    | 'ex205# bound here
    | [existential_ast3/v2.sail]:17:48-65
    | 17 |    if b == 0b0 then (64, unsigned(b @ a)) else (31, unsigned(a));
    |    |                                                ^---------------^
-   |    | 'ex154# bound here
+   |    | 'ex206# bound here
    | [existential_ast3/v2.sail]:17:48-65
    | 17 |    if b == 0b0 then (64, unsigned(b @ a)) else (31, unsigned(a));
    |    |                                                ^---------------^
-   |    | 'ex158# bound here
+   |    | 'ex210# bound here
    | 
diff --git a/test/typecheck/pass/existential_ast3/v3.expect b/test/typecheck/pass/existential_ast3/v3.expect
index 0e43cd52..585cf2c6 100644
--- a/test/typecheck/pass/existential_ast3/v3.expect
+++ b/test/typecheck/pass/existential_ast3/v3.expect
@@ -3,5 +3,5 @@ Type error:
 25 |    Some(Ctor(64, unsigned(0b0 @ b @ a)))
    |         ^-----------------------------^
    | Could not resolve quantifiers for Ctor
-   | * (datasize(64) & (0 <= 'ex197# & ('ex197# + 1) <= 64))
+   | * (datasize(64) & (0 <= 'ex249# & ('ex249# + 1) <= 64))
    | 
diff --git a/test/typecheck/pass/if_infer/v1.expect b/test/typecheck/pass/if_infer/v1.expect
index 011ecbdf..50bd530d 100644
--- a/test/typecheck/pass/if_infer/v1.expect
+++ b/test/typecheck/pass/if_infer/v1.expect
@@ -5,8 +5,8 @@ Type error:
    | No overloading for vector_access, tried:
    | * bitvector_access
    |    Could not resolve quantifiers for bitvector_access
-   |    * (0 <= 'ex115# & ('ex115# + 1) <= 3)
+   |    * (0 <= 'ex166# & ('ex166# + 1) <= 3)
    | * plain_vector_access
    |    Could not resolve quantifiers for plain_vector_access
-   |    * (0 <= 'ex118# & ('ex118# + 1) <= 3)
+   |    * (0 <= 'ex169# & ('ex169# + 1) <= 3)
    | 
diff --git a/test/typecheck/pass/if_infer/v2.expect b/test/typecheck/pass/if_infer/v2.expect
index 9a34f688..27b05208 100644
--- a/test/typecheck/pass/if_infer/v2.expect
+++ b/test/typecheck/pass/if_infer/v2.expect
@@ -5,8 +5,8 @@ Type error:
    | No overloading for vector_access, tried:
    | * bitvector_access
    |    Could not resolve quantifiers for bitvector_access
-   |    * (0 <= 'ex115# & ('ex115# + 1) <= 4)
+   |    * (0 <= 'ex166# & ('ex166# + 1) <= 4)
    | * plain_vector_access
    |    Could not resolve quantifiers for plain_vector_access
-   |    * (0 <= 'ex118# & ('ex118# + 1) <= 4)
+   |    * (0 <= 'ex169# & ('ex169# + 1) <= 4)
    | 
diff --git a/test/typecheck/pass/wf_specs.sail b/test/typecheck/pass/wf_specs.sail
new file mode 100644
index 00000000..2bacf7e0
--- /dev/null
+++ b/test/typecheck/pass/wf_specs.sail
@@ -0,0 +1,11 @@
+/* Example from https://github.com/rems-project/sail/issues/47 where a variable
+   name is mistakenly used at the type level, which wasn't caught before due to
+   the lack of a well-formedness check on specs.  This is the corrected version.
+   */
+
+default Order dec
+$include <prelude.sail>
+
+let 'THIRTY_TWO : atom(32) = 32
+
+val f : bits(32) -> bits('THIRTY_TWO)
diff --git a/test/typecheck/pass/wf_specs/wf_specs.expect b/test/typecheck/pass/wf_specs/wf_specs.expect
new file mode 100644
index 00000000..88844e18
--- /dev/null
+++ b/test/typecheck/pass/wf_specs/wf_specs.expect
@@ -0,0 +1,6 @@
+Type error:
+[wf_specs/wf_specs.sail]:10:25-35
+10 |val f : bits(32) -> bits(THIRTY_TWO)
+   |                         ^--------^
+   | Undefined synonym THIRTY_TWO
+   | 
diff --git a/test/typecheck/pass/wf_specs/wf_specs.sail b/test/typecheck/pass/wf_specs/wf_specs.sail
new file mode 100644
index 00000000..bb108ee3
--- /dev/null
+++ b/test/typecheck/pass/wf_specs/wf_specs.sail
@@ -0,0 +1,10 @@
+/* Example from https://github.com/rems-project/sail/issues/47 where a variable
+   name is mistakenly used at the type level, which wasn't caught before due to
+   the lack of a well-formedness check on specs. */
+
+default Order dec
+$include <prelude.sail>
+
+let THIRTY_TWO : atom(32) = 32
+
+val f : bits(32) -> bits(THIRTY_TWO)