Issues

• Str.from_utf8_lossy is about 10× slower than Str.from_utf8 on valid input

  Bug

  roc-lang/roc#11966 · Filter by author lukewilliamboswell opened on Oct 1, 2026

• Appending after List.drop_last copies the whole list once drop_last has two call sites

  Bug

  roc-lang/roc#11965 · Filter by author lukewilliamboswell opened on Oct 1, 2026

• Segfault deriving the hash of a cross-module record with a nested tag union inside a custom to_hash

  Bug

  roc-lang/roc#11963 · Filter by author lukewilliamboswell opened on Oct 1, 2026

• Checked-module cache serialization substantially increases peak memory

  Bug

  roc-lang/roc#11961 · Filter by author lukewilliamboswell opened on Oct 1, 2026
  

• Numeric literals allocate large per-occurrence type-constraint graphs

  Bug

  roc-lang/roc#11960 · Filter by author lukewilliamboswell opened on Oct 1, 2026
  

• Incorrect pattern matching

  canerror-messages
  Bug

  roc-lang/roc#11950 · Filter by author notramo opened on Oct 1, 2026
  

• Type mismatching suffix passes roc check then crash at runtime

  type checking
  Bug

  roc-lang/roc#11948 · Filter by author notramo opened on Oct 1, 2026
  

• expect allows control flow

  Bug

  roc-lang/roc#11947 · Filter by author notramo opened on Oct 1, 2026
  2

  

• Record builder accepts and silently drops one of duplicate fields

  canerror-messages
  Bug

  roc-lang/roc#11945 · Filter by author notramo opened on Sep 30, 2026

• Closure capture a reassigned var differs in boxy (miscompilation)

  boxy
  Bug

  roc-lang/roc#11944 · Filter by author notramo opened on Sep 30, 2026

• Associated method not found on tag union type

  error-messages
  Bug

  roc-lang/roc#11943 · Filter by author notramo opened on Sep 30, 2026

• roc test segfaults on effectful expect

  Bug

  roc-lang/roc#11942 · Filter by author notramo opened on Sep 30, 2026
  

• Associated items on an alias recommend old syntax

  error-messages
  Bug

  roc-lang/roc#11941 · Filter by author notramo opened on Sep 30, 2026

• Pure function allows calling effectful

  Bug

  roc-lang/roc#11940 · Filter by author notramo opened on Sep 30, 2026
  

• Exhaustiveness check allows invalid match

  type checking
  Bug

  roc-lang/roc#11939 · Filter by author notramo opened on Sep 30, 2026

• Nonexistent type crashes roc check

  type checking
  Bug

  roc-lang/roc#11938 · Filter by author notramo opened on Sep 30, 2026

• Unstable formatting

  formatting
  Bug

  roc-lang/roc#11936 · Filter by author notramo opened on Sep 30, 2026

• List.clear drops the capacity when its list is a parameter inferred as borrowed

  Bug

  roc-lang/roc#11934 · Filter by author lukewilliamboswell opened on Sep 30, 2026
  

• Dev builds copy a list var updated after an if statement whose branch reassigns another list and ends in a nested if

  Bug

  roc-lang/roc#11933 · Filter by author lukewilliamboswell opened on Sep 30, 2026
  

• roc check segfault (or hang) when storing nominally typed tag union into structurally typed location

  roc-lang/roc#11931 · Filter by author notramo opened on Sep 30, 2026

• roc fmt adds unnecessary blank line above first doc comment

  formatting
  roc-lang/roc#11930 · Filter by author notramo opened on Sep 30, 2026
  1

• roc fmt incorrectly removes indentation of comment

  formatting
  roc-lang/roc#11929 · Filter by author notramo opened on Sep 30, 2026

• roc fmt deletes comments in platform headers

  formatting
  Bug

  roc-lang/roc#11927 · Filter by author notramo opened on Sep 30, 2026

• roc fmt deletes comment after last item

  formatting
  Bug

  roc-lang/roc#11926 · Filter by author notramo opened on Sep 30, 2026

• LSP: no completions for builtin types nested inside another type (e.g. I64., Num.I64.)

  language-server
  Bug

  roc-lang/roc#11924 · Filter by author v4rm4n opened on Sep 30, 2026