Improved various error messages when handling unexpected types.

error: bad slot #1, expected string|symbol|keyword|buffer, got ...
error: bad slot #1, expected a string, symbol, keyword or buffer, got ...

bad s64 initializer: "donkey"
can not convert string "donkey" to s64

src/core/inttypes.c

@@ -138,7 +138,7 @@ int64_t janet_unwrap_s64(Janet x) {
             break;
         }
     }
-    janet_panicf("bad s64 initializer: %t", x);
+    janet_panicf("can not convert %t %q to 64 bit signed integer", x, x);
     return 0;
 }
 
@@ -169,7 +169,7 @@ uint64_t janet_unwrap_u64(Janet x) {
             break;
         }
     }
-    janet_panicf("bad u64 initializer: %t", x);
+    janet_panicf("can not convert %t %q to a 64 bit unsigned integer", x, x);
     return 0;
 }
 

src/core/pp.c

@@ -736,7 +736,7 @@ static void pushtypes(JanetBuffer *buffer, int types) {
             if (first) {
                 first = 0;
             } else {
-                janet_buffer_push_u8(buffer, '|');
+                janet_buffer_push_cstring(buffer, (types == 1) ? " or " : ", ");
             }
             janet_buffer_push_cstring(buffer, janet_type_names[i]);
         }