[REDACTED] (Dec 02 2023 at 17:22): [REDACTED] (Dec 02 2023 at 17:22):── MISSING FINAL EXPRESSION ───────────────────────────────────────── main.roc ─
I am partway through parsing a definition, but I got stuck here:
53│ subItemWalker =
54│ List.walk subsItems {invalidEncounters: Bool} \walkerState, walkerItem ->
55│ if walkerState.invalidEncounters == Bool.true then
56│ {invalidEncounters: Bool.true}
57│ else
58│ itemSplit = Str.split walkerItem " "
59│ countStrRaw = List.get itemSplit 0
60│ countStr =
61│ when countStrRaw is
62│ Ok val -> val
63│ Err OutOfBounds -> crash "Nope, doesn't work"
64│ count =
65│ when Str.toU32 countStr is
66│ Ok val -> val
67│ Err InvalidNumStr -> crash "Nope, doesn't work"
68│ # at this point, we got the count of cubes for this specific color.
69│ colorStrRaw = List.get itemSplit 1
70│ colorStr =
71│ when colorStrRaw is
72│ Ok val -> val
73│ Err OutOfBounds -> crash "Nope, doesn't work"
74│ # we also got the color name.
75│ when colorStr is
76│ "red" ->
77│ if count > 12 then
78│ { invalidEncounters: Bool.true }
79│ else
80│ { invalidEncounters: Bool.false }
81│ "green" ->
82│ if count > 13 then
83│ { invalidEncounters: Bool.true }
84│ else
85│ { invalidEncounters: Bool.false }
86│ "blue" ->
87│ if count > 14 then
88│ { invalidEncounters: Bool.true }
89│ else
90│ { invalidEncounters: Bool.false }
91│ _ -> { invalidEncounters: Bool.false }
^
This definition is missing a final expression. A nested definition
must be followed by either another definition, or an expression
x = 4
y = 2
x + y
The error means that roc is expecting some sort of value, but instead things are just stored in variables. As a small example:
invalid:
main : U32
main =
x = 7
y = 3
out = x + y
valid:
main : U32
main =
x = 7
y = 3
x + y
I've tried using the value returned from subItemWalker as return value, but I still get the same error.
── MISSING FINAL EXPRESSION ───────────────────────────────────────── main.roc ─
I am partway through parsing a definition, but I got stuck here:
92│ subItemWalker
^
This definition is missing a final expression. A nested definition
must be followed by either another definition, or an expression
So just looked at it, and at least from just that snippet of code, it seems there is an issue that may be partially confusing the compiler. That said, this issue may still be real based on context around this code.
Anyway, the bug is that in the List.walk line it is just written Bool instead of Bool.false. After changing that is the error fixed?
Brendan Hansknecht (Dec 02 2023 at 17:31):Otherwise, we may need more context of the surrounding scope to debug this.
[REDACTED] (Dec 02 2023 at 17:33):Unfortunately that did not fix it, where can I share my entire code? I was solving AoC :p
[REDACTED] (Dec 02 2023 at 17:35): Brian Carroll (Dec 02 2023 at 17:37):Looks like you now have exactly the same problem at the next scope outwards
Brian Carroll (Dec 02 2023 at 17:38):When define a thing like subWalker = or subsetExplorer = , you actually need to use it afterwards.
If the code defines a bunch of things and then doesn't use them, this error can happen.
[REDACTED] (Dec 02 2023 at 17:39):I actually don't have much experience with Roc in general, I thought, "hey, this language looks nice, might do some advent of code in it", and here I am, 4 hours later.
Brendan Hansknecht (Dec 02 2023 at 17:39):Changing the last two lines to:
subItemWalker.invalidEncounters
subsetExplorer
Then updating the other List.walk line to Bool.false instead of just Bool looks to work.
[REDACTED] (Dec 02 2023 at 17:41):Brendan Hansknecht said:
Changing the last two lines to:
subItemWalker.invalidEncounters subsetExplorerThen updating the other List.walk line to
Bool.falseinstead of justBoollooks to work.
Do you mean changing
_ -> { invalidEncounters: Bool.false }
subItemWalker
to that?
Brendan Hansknecht (Dec 02 2023 at 17:42):oh, sorry, still leave in the _ -> { invalidEncounters: Bool.false }
Brendan Hansknecht (Dec 02 2023 at 17:42):So just replacing subItemWalker with that
[REDACTED] (Dec 02 2023 at 17:42):gotchu
[REDACTED] (Dec 02 2023 at 17:45):okay, those errors seem to be gone now :exploding_head:
Brendan Hansknecht (Dec 02 2023 at 17:46):I guess we may need to improve that error message to help explain the issue better. Clearly the example didn't help here. Also the amount of code selected for the error may be too small in some cases.
Anton (Dec 02 2023 at 18:50):I made #6156 for improvements to this error message
Last updated: Jul 26 2025 at 12:14 UTC