Add test showing implicit type casts are banned for indexes

test/expected/hnsw_insert.out

@@ -9,7 +9,11 @@ set work_mem = '64kB';
 set client_min_messages = 'ERROR';
 CREATE TABLE small_world (
     id SERIAL PRIMARY KEY,
-    v REAL[2]
+    v REAL[2] -- this demonstates that postgres actually does not enforce real[] length as we actually insert vectors of length 3
+);
+CREATE TABLE small_world_int (
+    id SERIAL PRIMARY KEY,
+    v INTEGER[]
 );
 CREATE INDEX ON small_world USING hnsw (v) WITH (dim=3);
 INFO:  done init usearch index
@@ -28,6 +32,9 @@ INSERT INTO small_world (v) VALUES ('{0,0,1}'), ('{0,1,0}');
 INSERT INTO small_world (v) VALUES (NULL);
 -- Attempt to insert a row with an incorrect vector length
 \set ON_ERROR_STOP off
+-- Cannot create an hnsw index with implicit typecasts (trying to cast integer[] to real[], in this case)
+CREATE INDEX ON small_world_int USING hnsw (v dist_l2sq_ops) WITH (dim=3);
+ERROR:  operator class "dist_l2sq_ops" does not accept data type integer[]
 INSERT INTO small_world (v) VALUES ('{1,1,1,1}');
 ERROR:  Wrong number of dimensions: 4 instead of 3 expected
 \set ON_ERROR_STOP on

test/sql/hnsw_insert.sql

@@ -10,8 +10,14 @@ set client_min_messages = 'ERROR';
 
 CREATE TABLE small_world (
     id SERIAL PRIMARY KEY,
-    v REAL[2]
+    v REAL[2] -- this demonstates that postgres actually does not enforce real[] length as we actually insert vectors of length 3
 );
+
+CREATE TABLE small_world_int (
+    id SERIAL PRIMARY KEY,
+    v INTEGER[]
+);
+
 CREATE INDEX ON small_world USING hnsw (v) WITH (dim=3);
 SELECT _lantern_internal.validate_index('small_world_v_idx', false);
 
@@ -21,6 +27,8 @@ INSERT INTO small_world (v) VALUES (NULL);
 
 -- Attempt to insert a row with an incorrect vector length
 \set ON_ERROR_STOP off
+-- Cannot create an hnsw index with implicit typecasts (trying to cast integer[] to real[], in this case)
+CREATE INDEX ON small_world_int USING hnsw (v dist_l2sq_ops) WITH (dim=3);
 INSERT INTO small_world (v) VALUES ('{1,1,1,1}');
 \set ON_ERROR_STOP on