better errors for everything

benbellick · Dec 17, 2024 · 78223f9 · 78223f9
1 parent fb529c4
commit 78223f9
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Showing 2 changed files with 23 additions and 5 deletions.
diff --git a/src/decoders_deriver.ml b/src/decoders_deriver.ml
@@ -154,8 +154,17 @@ let rec expr_of_typ (typ : core_type)
       Location.raise_errorf ~loc
         "Cannot construct decoder for %s: cannot decode wildcard in type "
         (string_of_core_type typ)
-  | _ ->
-      Location.raise_errorf ~loc "Cannot construct decoder for %s"
+  | { ptyp_desc = Ptyp_alias _; _ } ->
+      Location.raise_errorf ~loc
+        "Cannot construct decoder for %s: cannot decode type alias"
+        (string_of_core_type typ)
+  | { ptyp_desc = Ptyp_variant _; _ } ->
+      Location.raise_errorf ~loc
+        "Cannot construct decoder for %s: cannot decode polymorphic variant"
+        (string_of_core_type typ)
+  | { ptyp_desc = Ptyp_extension _; _ } ->
+      Location.raise_errorf ~loc
+        "Cannot construct decoder for %s: cannot decode type extension point"
         (string_of_core_type typ)
 
 and expr_of_tuple ~loc ~substitutions ?lift typs =

diff --git a/src/encoders_deriver.ml b/src/encoders_deriver.ml
@@ -86,12 +86,21 @@ let rec expr_of_typ (typ : core_type) : expression =
         "Cannot construct encoder for %s: cannot encode explicitly polymorphic \
          types"
         (string_of_core_type typ)
-  | { ptyp_desc = Ptyp_any _; _ } ->
+  | { ptyp_desc = Ptyp_any; _ } ->
       Location.raise_errorf ~loc
         "Cannot construct encoder for %s: cannot encode wildcard in type "
         (string_of_core_type typ)
-  | _ ->
-      Location.raise_errorf ~loc "Cannot construct encoder for %s"
+  | { ptyp_desc = Ptyp_alias _; _ } ->
+      Location.raise_errorf ~loc
+        "Cannot construct encoder for %s: cannot encode type alias"
+        (string_of_core_type typ)
+  | { ptyp_desc = Ptyp_variant _; _ } ->
+      Location.raise_errorf ~loc
+        "Cannot construct encoder for %s: cannot encode polymorphic variant"
+        (string_of_core_type typ)
+  | { ptyp_desc = Ptyp_extension _; _ } ->
+      Location.raise_errorf ~loc
+        "Cannot construct encoder for %s: cannot encode type extension point"
         (string_of_core_type typ)
 
 and expr_of_tuple ~loc (* ~substitutions ?lift *) typs =