Issues

• --opt=speed compiles a record decoded through a custom parser_for to a trap when the field's parser updates two variables in a loop

  roc-lang/roc#12884 · Filter by author KouYuume opened on Nov 6, 2026

• == on a tag union reports "never resolved to a concrete type" when the value goes into a ? error tag and an earlier ? used a function from an unannotated top-level record

  roc-lang/roc#12883 · Filter by author niclas-ahden opened on Nov 6, 2026

• roc check crashes with "structural encoder evidence had no generated derivation" when a string passed to Json.to_str also goes into a tag in main!'s inferred error row

  roc-lang/roc#12882 · Filter by author niclas-ahden opened on Nov 6, 2026

• roc check takes cubic time to report a type mismatch on a static dispatch call in an unannotated function with many calls to the same method (30 s at 320 calls)

  roc-lang/roc#12881 · Filter by author niclas-ahden opened on Nov 6, 2026

• roc check passes but a program crashes with "dispatch on a value that can never exist" when a split_last(...).map_ok(...) result is printed and the split string goes into one branch's error tag

  roc-lang/roc#12879 · Filter by author niclas-ahden opened on Nov 6, 2026

• roc check panics with "instantiation widened a closed tag union" when a callback method's error row gains a tag and another function dispatches a method named like a roc-pg Client method

  roc-lang/roc#12878 · Filter by author niclas-ahden opened on Nov 6, 2026

• Building AFL++ for fuzzing fails on Zig 0.17: no field named lib_dir

  roc-lang/roc#12877 · Filter by author Anton-4-bot opened on Nov 6, 2026
  

• roc check never finishes when an unannotated function compares a Json.Parseable-constrained Try with == and returns it in a tag

  Bug

  roc-lang/roc#12873 · Filter by author niclas-ahden opened on Nov 5, 2026

• Monotype lowering blows up exponentially when an unused closure captures a function passed to a branching self-recursive closure

  Bug

  roc-lang/roc#12869 · Filter by author lukewilliamboswell opened on Nov 5, 2026
  

• Extra copy in complete if/else clause compare to a standlone if-clause early return + regular return

  roc-lang/roc#12868 · Filter by author zhenweigc opened on Nov 5, 2026

• Share content-named constants across native unit images in the fast dev link

  Task

  roc-lang/roc#12864 · Filter by author rtfeldman opened on Nov 4, 2026

• roc test --specialize=no segfaults after roc build: nominal type lookup omits the finalized program root

  Bug

  roc-lang/roc#12859 · Filter by author lukewilliamboswell opened on Nov 4, 2026
  

• For-loop over a fixed length + fixed item list is much slower than directly flatten the loop

  roc-lang/roc#12858 · Filter by author zhenweigc opened on Nov 4, 2026

• [new Boxy bug] A generic wrapper of a recursive type gets a composed layout without the recursion box that the committed layout has (--specialize=no segfault)

  roc-lang/roc#12855 · Filter by author Karakatiza666 opened on Nov 4, 2026

• Three LLVM passes still grow faster than linear with function size under --opt=speed

  Bug

  roc-lang/roc#12849 · Filter by author rtfeldman opened on Nov 4, 2026
  

• Boxy panic: body-local format method dispatching on the outer function's where clause

  boxy
  Bug

  roc-lang/roc#12844 · Filter by author rtfeldman opened on Nov 4, 2026
  

• Restoring a stored encoder built by a body-local helper with its own where clause panics under --specialize=yes

  Bug

  roc-lang/roc#12843 · Filter by author rtfeldman opened on Nov 4, 2026
  

• Two instantiations of a function with a body-local format type compute the same encoder result

  Bug

  roc-lang/roc#12842 · Filter by author rtfeldman opened on Nov 4, 2026
  

• Boxy ARC check fails restoring a stored closure that calls a body-local type's methods

  boxy
  Bug

  roc-lang/roc#12840 · Filter by author rtfeldman opened on Nov 4, 2026
  

• Warm roc check --specialize=yes on roc-pg's rebellion example repeats most of the cold work

  Bug

  roc-lang/roc#12839 · Filter by author rtfeldman opened on Nov 4, 2026
  

• roc test --specialize=yes panics in Lambda Solved for a body-local nominal over the body's type variable used at two types

  Bug

  roc-lang/roc#12838 · Filter by author rtfeldman opened on Nov 4, 2026
  

• Box.box of a callable with no captures allocates on every call; could use static storage

  Bug

  roc-lang/roc#12836 · Filter by author lukewilliamboswell opened on Nov 4, 2026
  

• Annotated polymorphic recursion hangs roc test and roc check under --specialize=yes

  Bug

  roc-lang/roc#12835 · Filter by author lukewilliamboswell opened on Nov 4, 2026
  

• --opt=speed writes into a shared Dict, so a retained alias changes (regression in nightly-2026-10-29)

  Bug

  roc-lang/roc#12834 · Filter by author lukewilliamboswell opened on Nov 4, 2026
  

• Incompatible pattern in match silently accepted

  Bug

  roc-lang/roc#12833 · Filter by author notramo opened on Nov 4, 2026