Merge branch 'roc-lang:main' into updating-docs

.github/FUNDING.yml

@@ -0,0 +1,3 @@
+# These are supported funding model platforms
+
+github: roc-lang

.github/workflows/nightly_macos_x86_64.yml

@@ -11,7 +11,10 @@ env:
 jobs:
   test-build-upload:
     name: build, test, package and upload nightly release
-    runs-on: [macos-12]
+    strategy:
+      matrix:
+        os: [ macos-11, macos-12 ]
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 120
     steps:
       - uses: actions/checkout@v3
@@ -35,23 +38,41 @@ jobs:
           command: build
           args: --release --locked
           
-      - name: execute rust tests
+      - name: execute rust tests if macos 12
+        if: endsWith(matrix.os, '12')
         uses: actions-rs/cargo@v1
         with:
           command: test
           args: --release --locked -- --skip opaque_wrap_function --skip bool_list_literal
           
+      - name: execute rust tests if macos 11
+        if: endsWith(matrix.os, '11')
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --release --locked -- --skip opaque_wrap_function --skip bool_list_literal --skip platform_switching_swift --skip swift_ui
+          # swift tests are skipped because of "Could not find or use auto-linked library 'swiftCompatibilityConcurrency'" on macos-11 x86_64 CI machine
+          # this issue may be caused by using older versions of XCode
+          
       - name: get commit SHA
         run:  echo "SHA=$(git rev-parse --short "$GITHUB_SHA")" >> $GITHUB_ENV
         
       - name: get date
         run: echo "DATE=$(date "+%Y-%m-%d")" >> $GITHUB_ENV
         
+      - name: get macos version if 11
+        if: endsWith(matrix.os, '11')
+        run: echo "MACOSVERSION=11" >> $GITHUB_ENV
+        
+      - name: get macos version if 12
+        if: endsWith(matrix.os, '12')
+        run: echo "MACOSVERSION=12" >> $GITHUB_ENV
+        
       - name: build file name
         env:
             DATE: ${{ env.DATE }}
             SHA: ${{ env.SHA }}
-        run: echo "RELEASE_TAR_FILENAME=roc_nightly-macos_x86_64-$DATE-$SHA.tar.gz" >> $GITHUB_ENV
+        run: echo "RELEASE_TAR_FILENAME=roc_nightly-macos_${MACOSVERSION}_x86_64-$DATE-$SHA.tar.gz" >> $GITHUB_ENV
         
       - name: package release
         run: ./ci/package_release.sh ${{ env.RELEASE_TAR_FILENAME }}

.github/workflows/ubuntu_x86_64.yml

@@ -45,6 +45,9 @@ jobs:
       - name: run `roc test` on Str builtins
         run: cargo run --locked --release -- test crates/compiler/builtins/roc/Str.roc && sccache --show-stats
 
+      - name: run `roc test` on Dict builtins
+        run: cargo run --locked --release -- test crates/compiler/builtins/roc/Dict.roc && sccache --show-stats
+
       #TODO pass --locked into the script here as well, this avoids rebuilding dependencies unnecessarily
       - name: wasm repl test
         run: crates/repl_test/test_wasm.sh && sccache --show-stats

crates/compiler/builtins/roc/Dict.roc

@@ -21,7 +21,9 @@ interface Dict
         Bool.{ Bool, Eq },
         Result.{ Result },
         List,
-        Num.{ Nat },
+        Str,
+        Num.{ Nat, U64, U8 },
+        Hash.{ Hasher },
     ]
 
 ## A [dictionary](https://en.wikipedia.org/wiki/Associative_array) that lets you can associate keys with values.
@@ -206,3 +208,412 @@ insertIfVacant = \dict, key, value ->
         dict
     else
         Dict.insert dict key value
+
+# We have decided not to expose the standard roc hashing algorithm.
+# This is to avoid external dependence and the need for versioning.
+# The current implementation is a form of [Wyhash final3](https://github.com/wangyi-fudan/wyhash/blob/a5995b98ebfa7bd38bfadc0919326d2e7aabb805/wyhash.h).
+# It is 64bit and little endian specific currently.
+# TODO: wyhash is slow for large keys, use something like cityhash if the keys are too long.
+# TODO: Add a builtin to distinguish big endian systems and change loading orders.
+# TODO: Switch out Wymum on systems with slow 128bit multiplication.
+LowLevelHasher := { originalSeed : U64, state : U64 } has [
+         Hasher {
+             addBytes,
+             addU8,
+             addU16,
+             addU32,
+             addU64,
+             addU128,
+             addI8,
+             addI16,
+             addI32,
+             addI64,
+             addI128,
+             complete,
+         },
+     ]
+
+# unsafe primitive that does not perform a bounds check
+# TODO hide behind an InternalList.roc module
+listGetUnsafe : List a, Nat -> a
+
+createLowLevelHasher : { seed ?U64 } -> LowLevelHasher
+createLowLevelHasher = \{ seed ? 0x526F_6352_616E_643F } ->
+    @LowLevelHasher { originalSeed: seed, state: seed }
+
+combineState : LowLevelHasher, { a : U64, b : U64, seed : U64, length : U64 } -> LowLevelHasher
+combineState = \@LowLevelHasher { originalSeed, state }, { a, b, seed, length } ->
+    tmp = wymix (Num.bitwiseXor wyp1 a) (Num.bitwiseXor seed b)
+    hash = wymix (Num.bitwiseXor wyp1 length) tmp
+
+    @LowLevelHasher { originalSeed, state: wymix state hash }
+
+complete = \@LowLevelHasher { state } -> state
+
+addI8 = \hasher, i8 ->
+    addU8 hasher (Num.toU8 i8)
+addI16 = \hasher, i16 ->
+    addU16 hasher (Num.toU16 i16)
+addI32 = \hasher, i32 ->
+    addU32 hasher (Num.toU32 i32)
+addI64 = \hasher, i64 ->
+    addU64 hasher (Num.toU64 i64)
+addI128 = \hasher, i128 ->
+    addU128 hasher (Num.toU128 i128)
+
+# These implementations hash each value individually with the seed and then mix
+# the resulting hash with the state. There are other options that may be faster
+# like using the output of the last hash as the seed to the current hash.
+# I am simply not sure the tradeoffs here. Theoretically this method is more sound.
+# Either way, the performance will be similar and we can change this later.
+addU8 = \@LowLevelHasher { originalSeed, state }, u8 ->
+    seed = Num.bitwiseXor originalSeed wyp0
+    p0 = Num.toU64 u8
+    a =
+        Num.shiftLeftBy p0 16
+        |> Num.bitwiseOr (Num.shiftLeftBy p0 8)
+        |> Num.bitwiseOr p0
+    b = 0
+
+    combineState (@LowLevelHasher { originalSeed, state }) { a, b, seed, length: 1 }
+
+addU16 = \@LowLevelHasher { originalSeed, state }, u16 ->
+    seed = Num.bitwiseXor originalSeed wyp0
+    p0 = Num.bitwiseAnd u16 0xFF |> Num.toU64
+    p1 = Num.shiftRightZfBy u16 8 |> Num.toU64
+    a =
+        Num.shiftLeftBy p0 16
+        |> Num.bitwiseOr (Num.shiftLeftBy p1 8)
+        |> Num.bitwiseOr p1
+    b = 0
+
+    combineState (@LowLevelHasher { originalSeed, state }) { a, b, seed, length: 2 }
+
+addU32 = \@LowLevelHasher { originalSeed, state }, u32 ->
+    seed = Num.bitwiseXor originalSeed wyp0
+    p0 = Num.toU64 u32
+    a = Num.shiftLeftBy p0 32 |> Num.bitwiseOr p0
+
+    combineState (@LowLevelHasher { originalSeed, state }) { a, b: a, seed, length: 4 }
+
+addU64 = \@LowLevelHasher { originalSeed, state }, u64 ->
+    seed = Num.bitwiseXor originalSeed wyp0
+    p0 = Num.bitwiseAnd 0xFFFF_FFFF u64
+    p1 = Num.shiftRightZfBy u64 32
+    a = Num.shiftLeftBy p0 32 |> Num.bitwiseOr p1
+    b = Num.shiftLeftBy p1 32 |> Num.bitwiseOr p0
+
+    combineState (@LowLevelHasher { originalSeed, state }) { a, b, seed, length: 8 }
+
+addU128 = \@LowLevelHasher { originalSeed, state }, u128 ->
+    seed = Num.bitwiseXor originalSeed wyp0
+    lower = u128 |> Num.toU64
+    upper = Num.shiftRightZfBy u128 64 |> Num.toU64
+    p0 = Num.bitwiseAnd 0xFFFF_FFFF lower
+    p1 = Num.shiftRightZfBy lower 32 |> Num.bitwiseAnd 0xFFFF_FFFF
+    p2 = Num.bitwiseAnd 0xFFFF_FFFF upper
+    p3 = Num.shiftRightZfBy upper 32 |> Num.bitwiseAnd 0xFFFF_FFFF
+    a = Num.shiftLeftBy p0 32 |> Num.bitwiseOr p2
+    b = Num.shiftLeftBy p3 32 |> Num.bitwiseOr p1
+
+    combineState (@LowLevelHasher { originalSeed, state }) { a, b, seed, length: 16 }
+
+addBytes : LowLevelHasher, List U8 -> LowLevelHasher
+addBytes = \@LowLevelHasher { originalSeed, state }, list ->
+    length = List.len list
+    seed = Num.bitwiseXor originalSeed wyp0
+    abs =
+        if length <= 16 then
+            if length >= 4 then
+                x = Num.shiftRightZfBy length 3 |> Num.shiftLeftBy 2
+                a = Num.bitwiseOr (wyr4 list 0 |> Num.shiftLeftBy 32) (wyr4 list x)
+                b =
+                    (wyr4 list (Num.subWrap length 4) |> Num.shiftLeftBy 32)
+                    |> Num.bitwiseOr (wyr4 list (Num.subWrap length 4 |> Num.subWrap x))
+
+                { a, b, seed }
+            else if length > 0 then
+                { a: wyr3 list 0 length, b: 0, seed }
+            else
+                { a: 0, b: 0, seed }
+        else if length <= 48 then
+            hashBytesHelper16 seed list 0 length
+        else
+            hashBytesHelper48 seed seed seed list 0 length
+
+    combineState (@LowLevelHasher { originalSeed, state }) { a: abs.a, b: abs.b, seed: abs.seed, length: Num.toU64 length }
+
+hashBytesHelper48 : U64, U64, U64, List U8, Nat, Nat -> { a : U64, b : U64, seed : U64 }
+hashBytesHelper48 = \seed, see1, see2, list, index, remaining ->
+    newSeed = wymix (Num.bitwiseXor (wyr8 list index) wyp1) (Num.bitwiseXor (wyr8 list (Num.addWrap index 8)) seed)
+    newSee1 = wymix (Num.bitwiseXor (wyr8 list (Num.addWrap index 16)) wyp2) (Num.bitwiseXor (wyr8 list (Num.addWrap index 24)) see1)
+    newSee2 = wymix (Num.bitwiseXor (wyr8 list (Num.addWrap index 32)) wyp3) (Num.bitwiseXor (wyr8 list (Num.addWrap index 40)) see2)
+    newRemaining = Num.subWrap remaining 48
+    newIndex = Num.addWrap index 48
+
+    if newRemaining > 48 then
+        hashBytesHelper48 newSeed newSee1 newSee2 list newIndex newRemaining
+    else if newRemaining > 16 then
+        finalSeed = Num.bitwiseXor newSee2 (Num.bitwiseXor newSee1 newSeed)
+
+        hashBytesHelper16 finalSeed list newIndex newRemaining
+    else
+        finalSeed = Num.bitwiseXor newSee2 (Num.bitwiseXor newSee1 newSeed)
+
+        { a: wyr8 list (Num.subWrap newRemaining 16 |> Num.addWrap newIndex), b: wyr8 list (Num.subWrap newRemaining 8 |> Num.addWrap newIndex), seed: finalSeed }
+
+hashBytesHelper16 : U64, List U8, Nat, Nat -> { a : U64, b : U64, seed : U64 }
+hashBytesHelper16 = \seed, list, index, remaining ->
+    newSeed = wymix (Num.bitwiseXor (wyr8 list index) wyp1) (Num.bitwiseXor (wyr8 list (Num.addWrap index 8)) seed)
+    newRemaining = Num.subWrap remaining 16
+    newIndex = Num.addWrap index 16
+
+    if newRemaining <= 16 then
+        { a: wyr8 list (Num.subWrap newRemaining 16 |> Num.addWrap newIndex), b: wyr8 list (Num.subWrap newRemaining 8 |> Num.addWrap newIndex), seed: newSeed }
+    else
+        hashBytesHelper16 newSeed list newIndex newRemaining
+
+wyp0 : U64
+wyp0 = 0xa0761d6478bd642f
+wyp1 : U64
+wyp1 = 0xe7037ed1a0b428db
+wyp2 : U64
+wyp2 = 0x8ebc6af09c88c6e3
+wyp3 : U64
+wyp3 = 0x589965cc75374cc3
+
+wymix : U64, U64 -> U64
+wymix = \a, b ->
+    { lower, upper } = wymum a b
+
+    Num.bitwiseXor lower upper
+
+wymum : U64, U64 -> { lower : U64, upper : U64 }
+wymum = \a, b ->
+    r = Num.toU128 a * Num.toU128 b
+    lower = Num.toU64 r
+    upper = Num.shiftRightZfBy r 64 |> Num.toU64
+
+    # This is the more robust form.
+    # { lower: Num.bitwiseXor a lower, upper: Num.bitwiseXor b upper }
+    { lower, upper }
+
+# Get the next 8 bytes as a U64
+wyr8 : List U8, Nat -> U64
+wyr8 = \list, index ->
+    # With seamless slices and Num.fromBytes, this should be possible to make faster and nicer.
+    # It would also deal with the fact that on big endian systems we want to invert the order here.
+    # Without seamless slices, we would need fromBytes to take an index.
+    p1 = listGetUnsafe list index |> Num.toU64
+    p2 = listGetUnsafe list (Num.addWrap index 1) |> Num.toU64
+    p3 = listGetUnsafe list (Num.addWrap index 2) |> Num.toU64
+    p4 = listGetUnsafe list (Num.addWrap index 3) |> Num.toU64
+    p5 = listGetUnsafe list (Num.addWrap index 4) |> Num.toU64
+    p6 = listGetUnsafe list (Num.addWrap index 5) |> Num.toU64
+    p7 = listGetUnsafe list (Num.addWrap index 6) |> Num.toU64
+    p8 = listGetUnsafe list (Num.addWrap index 7) |> Num.toU64
+    a = Num.bitwiseOr p1 (Num.shiftLeftBy p2 8)
+    b = Num.bitwiseOr (Num.shiftLeftBy p3 16) (Num.shiftLeftBy p4 24)
+    c = Num.bitwiseOr (Num.shiftLeftBy p5 32) (Num.shiftLeftBy p6 40)
+    d = Num.bitwiseOr (Num.shiftLeftBy p7 48) (Num.shiftLeftBy p8 56)
+
+    Num.bitwiseOr (Num.bitwiseOr a b) (Num.bitwiseOr c d)
+
+# Get the next 4 bytes as a U64 with some shifting.
+wyr4 : List U8, Nat -> U64
+wyr4 = \list, index ->
+    p1 = listGetUnsafe list index |> Num.toU64
+    p2 = listGetUnsafe list (Num.addWrap index 1) |> Num.toU64
+    p3 = listGetUnsafe list (Num.addWrap index 2) |> Num.toU64
+    p4 = listGetUnsafe list (Num.addWrap index 3) |> Num.toU64
+    a = Num.bitwiseOr p1 (Num.shiftLeftBy p2 8)
+    b = Num.bitwiseOr (Num.shiftLeftBy p3 16) (Num.shiftLeftBy p4 24)
+
+    Num.bitwiseOr a b
+
+# Get the next K bytes with some shifting.
+# K must be 3 or less.
+wyr3 : List U8, Nat, Nat -> U64
+wyr3 = \list, index, k ->
+    # ((uint64_t)p[0])<<16)|(((uint64_t)p[k>>1])<<8)|p[k-1]
+    p1 = listGetUnsafe list index |> Num.toU64
+    p2 = listGetUnsafe list (Num.shiftRightZfBy k 1 |> Num.addWrap index) |> Num.toU64
+    p3 = listGetUnsafe list (Num.subWrap k 1 |> Num.addWrap index) |> Num.toU64
+    a = Num.bitwiseOr (Num.shiftLeftBy p1 16) (Num.shiftLeftBy p2 8)
+
+    Num.bitwiseOr a p3
+
+# TODO: would be great to have table driven expects for this.
+# Would also be great to have some sort of property based hasher
+# where we can compare `addU*` functions to the `addBytes` function.
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addBytes []
+        |> complete
+
+    hash == 0x1C3F_F8BF_07F9_B0B3
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addBytes [0x42]
+        |> complete
+
+    hash == 0x8F9F_0A1E_E06F_0D52
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addU8 0x42
+        |> complete
+
+    hash == 0x8F9F_0A1E_E06F_0D52
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addBytes [0xFF, 0xFF]
+        |> complete
+
+    hash == 0x86CC_8B71_563F_F084
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addU16 0xFFFF
+        |> complete
+
+    hash == 0x86CC_8B71_563F_F084
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addBytes [0x36, 0xA7]
+        |> complete
+
+    hash == 0xD1A5_0F24_2536_84F8
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addU16 0xA736
+        |> complete
+
+    hash == 0xD1A5_0F24_2536_84F8
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addBytes [0x00, 0x00, 0x00, 0x00]
+        |> complete
+
+    hash == 0x3762_ACB1_7604_B541
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addU32 0x0000_0000
+        |> complete
+
+    hash == 0x3762_ACB1_7604_B541
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addBytes [0xA9, 0x2F, 0xEE, 0x21]
+        |> complete
+
+    hash == 0x20F3_3FD7_D32E_C7A9
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addU32 0x21EE_2FA9
+        |> complete
+
+    hash == 0x20F3_3FD7_D32E_C7A9
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addBytes [0x5D, 0x66, 0xB1, 0x8F, 0x68, 0x44, 0xC7, 0x03, 0xE1, 0xDD, 0x23, 0x34, 0xBB, 0x9A, 0x42, 0xA7]
+        |> complete
+
+    hash == 0xA16F_DDAA_C167_74C7
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addU128 0xA742_9ABB_3423_DDE1_03C7_4468_8FB1_665D
+        |> complete
+
+    hash == 0xA16F_DDAA_C167_74C7
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> Hash.hashStrBytes "abcdefghijklmnopqrstuvwxyz"
+        |> complete
+
+    hash == 0xBEE0_A8FD_E990_D285
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> Hash.hashStrBytes "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+        |> complete
+
+    hash == 0xB3C5_8528_9D82_A6EF
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> Hash.hashStrBytes "1234567890123456789012345678901234567890123456789012345678901234567890"
+        |> complete
+
+    hash == 0xDB6B_7997_7A55_BA03
+
+expect
+    hash =
+        createLowLevelHasher {}
+        |> addBytes (List.repeat 0x77 100)
+        |> complete
+
+    hash == 0x171F_EEE2_B764_8E5E
+
+# Note, had to specify u8 in the lists below to avoid ability type resolution error.
+# Apparently it won't pick the default integer.
+expect
+    hash =
+        createLowLevelHasher {}
+        |> Hash.hashUnordered [8u8, 82u8, 3u8, 8u8, 24u8] List.walk
+        |> complete
+
+    hash == 0x999F_B530_3529_F17D
+
+expect
+    hash1 =
+        createLowLevelHasher {}
+        |> Hash.hashUnordered ([0u8, 1u8, 2u8, 3u8, 4u8]) List.walk
+        |> complete
+
+    hash2 =
+        createLowLevelHasher {}
+        |> Hash.hashUnordered [4u8, 3u8, 2u8, 1u8, 0u8] List.walk
+        |> complete
+
+    hash1 == hash2
+
+expect
+    hash1 =
+        createLowLevelHasher {}
+        |> Hash.hashUnordered [0u8, 1u8, 2u8, 3u8, 4u8] List.walk
+        |> complete
+
+    hash2 =
+        createLowLevelHasher {}
+        |> Hash.hashUnordered [4u8, 3u8, 2u8, 1u8, 0u8, 0u8] List.walk
+        |> complete
+
+    hash1 != hash2

crates/compiler/builtins/roc/Hash.roc

@@ -17,6 +17,7 @@ interface Hash
         complete,
         hashStrBytes,
         hashList,
+        hashUnordered,
     ] imports [
         List,
         Str,
@@ -75,10 +76,33 @@ Hasher has
 
 ## Adds a string into a [Hasher] by hashing its UTF-8 bytes.
 hashStrBytes = \hasher, s ->
-    Str.walkUtf8WithIndex s hasher \accumHasher, byte, _ ->
+    addBytes hasher (Str.toUtf8 s)
-        addU8 accumHasher byte
 
 ## Adds a list of [Hash]able elements to a [Hasher] by hashing each element.
 hashList = \hasher, lst ->
     List.walk lst hasher \accumHasher, elem ->
         hash accumHasher elem
+
+## Adds a container of [Hash]able elements to a [Hasher] by hashing each element.
+## The container is iterated using the walk method passed in.
+## The order of the elements does not affect the final hash.
+hashUnordered = \hasher, container, walk ->
+    walk
+        container
+        0
+        (\accum, elem ->
+            x =
+                # Note, we intentionally copy the hasher in every iteration.
+                # Having the same base state is required for unordered hashing.
+                hasher
+                |> hash elem
+                |> complete
+            nextAccum = Num.addWrap accum x
+
+            if nextAccum < accum then
+                # we don't want to lose a bit of entropy on overflow, so add it back in.
+                Num.addWrap nextAccum 1
+            else
+                nextAccum
+        )
+    |> \accum -> addU64 hasher accum

crates/compiler/can/src/annotation.rs

@@ -553,7 +553,7 @@ fn can_annotation_help(
                     references,
                 );
 
-                args.push(arg_ann);
+                args.push(Loc::at(arg.region, arg_ann));
             }
 
             match scope.lookup_alias(symbol) {
@@ -573,8 +573,14 @@ fn can_annotation_help(
 
                     let mut type_var_to_arg = Vec::new();
 
-                    for (_, arg_ann) in alias.type_variables.iter().zip(args) {
+                    for (alias_arg, arg_ann) in alias.type_variables.iter().zip(args) {
-                        type_var_to_arg.push(arg_ann);
+                        type_var_to_arg.push(Loc::at(
+                            arg_ann.region,
+                            OptAbleType {
+                                typ: arg_ann.value,
+                                opt_ability: alias_arg.value.opt_bound_ability,
+                            },
+                        ));
                     }
 
                     let mut lambda_set_variables =

crates/compiler/can/src/builtins.rs

@@ -70,6 +70,7 @@ macro_rules! map_symbol_to_lowlevel_and_arity {
             // Below, we explicitly handle some exceptions to the pattern where a lowlevel maps
             // directly to a symbol. If you are unsure if your lowlevel is an exception, assume
             // that it isn't and just see if that works.
+            #[allow(unreachable_patterns)] // multiple symbols can map to one low-level
             match lowlevel {
                 $(
                 LowLevel::$lowlevel => Symbol::$symbol,
@@ -144,6 +145,8 @@ map_symbol_to_lowlevel_and_arity! {
     ListSwap; LIST_SWAP; 3,
     ListGetCapacity; LIST_CAPACITY; 1,
 
+    ListGetUnsafe; DICT_LIST_GET_UNSAFE; 2,
+
     NumAdd; NUM_ADD; 2,
     NumAddWrap; NUM_ADD_WRAP; 2,
     NumAddChecked; NUM_ADD_CHECKED_LOWLEVEL; 2,

crates/compiler/can/src/def.rs

@@ -829,7 +829,15 @@ fn canonicalize_opaque<'a>(
                 type_arguments: alias
                     .type_variables
                     .iter()
-                    .map(|_| Type::Variable(var_store.fresh()))
+                    .map(|alias_var| {
+                        Loc::at(
+                            alias_var.region,
+                            OptAbleType {
+                                typ: Type::Variable(var_store.fresh()),
+                                opt_ability: alias_var.value.opt_bound_ability,
+                            },
+                        )
+                    })
                     .collect(),
                 lambda_set_variables: alias
                     .lambda_set_variables

crates/compiler/constrain/src/builtins.rs

@@ -3,7 +3,7 @@ use roc_can::constraint::{Constraint, Constraints};
 use roc_can::expected::Expected::{self, *};
 use roc_can::num::{FloatBound, FloatWidth, IntBound, IntLitWidth, NumBound, SignDemand};
 use roc_module::symbol::Symbol;
-use roc_region::all::Region;
+use roc_region::all::{Loc, Region};
 use roc_types::num::{NumericRange, SingleQuoteBound};
 use roc_types::subs::Variable;
 use roc_types::types::Type::{self, *};
@@ -198,7 +198,11 @@ pub fn num_literal(
 
 #[inline(always)]
 pub fn builtin_type(symbol: Symbol, args: Vec<Type>) -> Type {
-    Type::Apply(symbol, args, Region::zero())
+    Type::Apply(
+        symbol,
+        args.into_iter().map(Loc::at_zero).collect(),
+        Region::zero(),
+    )
 }
 
 #[inline(always)]

crates/compiler/module/src/symbol.rs

@@ -1433,6 +1433,8 @@ define_builtins! {
         15 DICT_WITH_CAPACITY: "withCapacity"
         16 DICT_CAPACITY: "capacity"
         17 DICT_UPDATE: "update"
+
+        18 DICT_LIST_GET_UNSAFE: "listGetUnsafe"
     }
     9 SET: "Set" => {
         0 SET_SET: "Set" exposed_type=true // the Set.Set type alias
@@ -1532,6 +1534,7 @@ define_builtins! {
         14 HASH_COMPLETE: "complete"
         15 HASH_HASH_STR_BYTES: "hashStrBytes"
         16 HASH_HASH_LIST: "hashList"
+        17 HASH_HASH_UNORDERED: "hashUnordered"
     }
     14 JSON: "Json" => {
         0 JSON_JSON: "Json"

crates/compiler/solve/src/ability.rs

@@ -50,7 +50,14 @@ pub struct PendingDerivesTable(
 );
 
 impl PendingDerivesTable {
-    pub fn new(subs: &mut Subs, aliases: &mut Aliases, pending_derives: PendingDerives) -> Self {
+    pub fn new(
+        subs: &mut Subs,
+        aliases: &mut Aliases,
+        pending_derives: PendingDerives,
+        problems: &mut Vec<TypeError>,
+        abilities_store: &mut AbilitiesStore,
+        obligation_cache: &mut ObligationCache,
+    ) -> Self {
         let mut table = VecMap::with_capacity(pending_derives.len());
 
         for (opaque, (typ, derives)) in pending_derives.into_iter() {
@@ -66,8 +73,16 @@ impl PendingDerivesTable {
                 let derive_key = RequestedDeriveKey { opaque, ability };
 
                 // Neither rank nor pools should matter here.
-                let opaque_var =
+                let opaque_var = type_to_var(
-                    type_to_var(subs, Rank::toplevel(), &mut Pools::default(), aliases, &typ);
+                    subs,
+                    Rank::toplevel(),
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    &mut Pools::default(),
+                    aliases,
+                    &typ,
+                );
                 let real_var = match subs.get_content_without_compacting(opaque_var) {
                     Content::Alias(_, _, real_var, AliasKind::Opaque) => real_var,
                     _ => internal_error!("Non-opaque in derives table"),

crates/compiler/solve/src/solve.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::too_many_arguments)]
+
 use crate::ability::{
     resolve_ability_specialization, type_implementing_specialization, AbilityImplError,
     CheckedDerives, ObligationCache, PendingDerivesTable, Resolved,
@@ -274,6 +276,9 @@ impl Aliases {
         subs: &mut Subs,
         rank: Rank,
         pools: &mut Pools,
+        problems: &mut Vec<TypeError>,
+        abilities_store: &AbilitiesStore,
+        obligation_cache: &mut ObligationCache,
         arena: &bumpalo::Bump,
         symbol: Symbol,
         alias_variables: AliasVariables,
@@ -375,7 +380,18 @@ impl Aliases {
         if !can_reuse_old_definition {
             let mut typ = typ.clone();
             typ.substitute_variables(&substitutions);
-            let alias_variable = type_to_variable(subs, rank, pools, arena, self, &typ, false);
+            let alias_variable = type_to_variable(
+                subs,
+                rank,
+                pools,
+                problems,
+                abilities_store,
+                obligation_cache,
+                arena,
+                self,
+                &typ,
+                false,
+            );
             (alias_variable, kind)
         } else {
             if !substitutions.is_empty() {
@@ -389,7 +405,18 @@ impl Aliases {
             // assumption: an alias does not (transitively) syntactically contain itself
             // (if it did it would have to be a recursive tag union, which we should have fixed up
             // during canonicalization)
-            let alias_variable = type_to_variable(subs, rank, pools, arena, self, &t, false);
+            let alias_variable = type_to_variable(
+                subs,
+                rank,
+                pools,
+                problems,
+                abilities_store,
+                obligation_cache,
+                arena,
+                self,
+                &t,
+                false,
+            );
 
             {
                 match self.aliases.iter_mut().find(|(s, _, _, _)| *s == symbol) {
@@ -562,7 +589,14 @@ fn run_in_place(
     let mut obligation_cache = ObligationCache::default();
     let mut awaiting_specializations = AwaitingSpecializations::default();
 
-    let pending_derives = PendingDerivesTable::new(subs, aliases, pending_derives);
+    let pending_derives = PendingDerivesTable::new(
+        subs,
+        aliases,
+        pending_derives,
+        problems,
+        abilities_store,
+        &mut obligation_cache,
+    );
     let CheckedDerives {
         legal_derives: _,
         problems: derives_problems,
@@ -687,6 +721,9 @@ fn solve(
                     constraints,
                     rank,
                     pools,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
                     aliases,
                     subs,
                     let_con.def_types,
@@ -747,6 +784,9 @@ fn solve(
                     constraints,
                     next_rank,
                     pools,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
                     aliases,
                     subs,
                     let_con.def_types,
@@ -858,11 +898,29 @@ fn solve(
             Eq(roc_can::constraint::Eq(type_index, expectation_index, category_index, region)) => {
                 let category = &constraints.categories[category_index.index()];
 
-                let actual =
+                let actual = either_type_index_to_var(
-                    either_type_index_to_var(constraints, subs, rank, pools, aliases, *type_index);
+                    constraints,
+                    subs,
+                    rank,
+                    pools,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    aliases,
+                    *type_index,
+                );
 
                 let expectation = &constraints.expectations[expectation_index.index()];
-                let expected = type_to_var(subs, rank, pools, aliases, expectation.get_type_ref());
+                let expected = type_to_var(
+                    subs,
+                    rank,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    pools,
+                    aliases,
+                    expectation.get_type_ref(),
+                );
 
                 match unify(&mut UEnv::new(subs), actual, expected, Mode::EQ) {
                     Success {
@@ -927,6 +985,9 @@ fn solve(
                     subs,
                     rank,
                     pools,
+                    &mut vec![], // don't report any extra errors
+                    abilities_store,
+                    obligation_cache,
                     aliases,
                     *source_index,
                 );
@@ -962,8 +1023,16 @@ fn solve(
                         let actual = deep_copy_var_in(subs, rank, pools, var, arena);
                         let expectation = &constraints.expectations[expectation_index.index()];
 
-                        let expected =
+                        let expected = type_to_var(
-                            type_to_var(subs, rank, pools, aliases, expectation.get_type_ref());
+                            subs,
+                            rank,
+                            problems,
+                            abilities_store,
+                            obligation_cache,
+                            pools,
+                            aliases,
+                            expectation.get_type_ref(),
+                        );
 
                         match unify(&mut UEnv::new(subs), actual, expected, Mode::EQ) {
                             Success {
@@ -1048,11 +1117,29 @@ fn solve(
             | PatternPresence(type_index, expectation_index, category_index, region) => {
                 let category = &constraints.pattern_categories[category_index.index()];
 
-                let actual =
+                let actual = either_type_index_to_var(
-                    either_type_index_to_var(constraints, subs, rank, pools, aliases, *type_index);
+                    constraints,
+                    subs,
+                    rank,
+                    pools,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    aliases,
+                    *type_index,
+                );
 
                 let expectation = &constraints.pattern_expectations[expectation_index.index()];
-                let expected = type_to_var(subs, rank, pools, aliases, expectation.get_type_ref());
+                let expected = type_to_var(
+                    subs,
+                    rank,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    pools,
+                    aliases,
+                    expectation.get_type_ref(),
+                );
 
                 let mode = match constraint {
                     PatternPresence(..) => Mode::PRESENT,
@@ -1209,8 +1296,17 @@ fn solve(
                 }
             }
             IsOpenType(type_index) => {
-                let actual =
+                let actual = either_type_index_to_var(
-                    either_type_index_to_var(constraints, subs, rank, pools, aliases, *type_index);
+                    constraints,
+                    subs,
+                    rank,
+                    pools,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    aliases,
+                    *type_index,
+                );
 
                 open_tag_union(subs, actual);
 
@@ -1231,12 +1327,30 @@ fn solve(
                 let tys = &constraints.types[types.indices()];
                 let pattern_category = &constraints.pattern_categories[pattern_category.index()];
 
-                let actual = type_to_var(subs, rank, pools, aliases, typ);
+                let actual = type_to_var(
+                    subs,
+                    rank,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    pools,
+                    aliases,
+                    typ,
+                );
                 let tag_ty = Type::TagUnion(
                     vec![(tag_name.clone(), tys.to_vec())],
                     TypeExtension::Closed,
                 );
-                let includes = type_to_var(subs, rank, pools, aliases, &tag_ty);
+                let includes = type_to_var(
+                    subs,
+                    rank,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    pools,
+                    aliases,
+                    &tag_ty,
+                );
 
                 match unify(&mut UEnv::new(subs), actual, includes, Mode::PRESENT) {
                     Success {
@@ -1337,10 +1451,28 @@ fn solve(
                     }
                 };
 
-                let real_var =
+                let real_var = either_type_index_to_var(
-                    either_type_index_to_var(constraints, subs, rank, pools, aliases, real_var);
+                    constraints,
+                    subs,
+                    rank,
+                    pools,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    aliases,
+                    real_var,
+                );
 
-                let branches_var = type_to_var(subs, rank, pools, aliases, expected_type);
+                let branches_var = type_to_var(
+                    subs,
+                    rank,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    pools,
+                    aliases,
+                    expected_type,
+                );
 
                 let real_content = subs.get_content_without_compacting(real_var);
                 let branches_content = subs.get_content_without_compacting(branches_var);
@@ -1889,6 +2021,9 @@ impl LocalDefVarsVec<(Symbol, Loc<Variable>)> {
         constraints: &Constraints,
         rank: Rank,
         pools: &mut Pools,
+        problems: &mut Vec<TypeError>,
+        abilities_store: &mut AbilitiesStore,
+        obligation_cache: &mut ObligationCache,
         aliases: &mut Aliases,
         subs: &mut Subs,
         def_types_slice: roc_can::constraint::DefTypes,
@@ -1899,7 +2034,16 @@ impl LocalDefVarsVec<(Symbol, Loc<Variable>)> {
         let mut local_def_vars = Self::with_length(types_slice.len());
 
         for (&(symbol, region), typ) in (loc_symbols_slice.iter()).zip(types_slice) {
-            let var = type_to_var(subs, rank, pools, aliases, typ);
+            let var = type_to_var(
+                subs,
+                rank,
+                problems,
+                abilities_store,
+                obligation_cache,
+                pools,
+                aliases,
+                typ,
+            );
 
             local_def_vars.push((symbol, Loc { value: var, region }));
         }
@@ -1930,6 +2074,9 @@ fn either_type_index_to_var(
     subs: &mut Subs,
     rank: Rank,
     pools: &mut Pools,
+    problems: &mut Vec<TypeError>,
+    abilities_store: &mut AbilitiesStore,
+    obligation_cache: &mut ObligationCache,
     aliases: &mut Aliases,
     either_type_index: roc_collections::soa::EitherIndex<Type, Variable>,
 ) -> Variable {
@@ -1937,7 +2084,16 @@ fn either_type_index_to_var(
         Ok(type_index) => {
             let typ = &constraints.types[type_index.index()];
 
-            type_to_var(subs, rank, pools, aliases, typ)
+            type_to_var(
+                subs,
+                rank,
+                problems,
+                abilities_store,
+                obligation_cache,
+                pools,
+                aliases,
+                typ,
+            )
         }
         Err(var_index) => {
             // we cheat, and  store the variable directly in the index
@@ -1949,6 +2105,9 @@ fn either_type_index_to_var(
 pub(crate) fn type_to_var(
     subs: &mut Subs,
     rank: Rank,
+    problems: &mut Vec<TypeError>,
+    abilities_store: &mut AbilitiesStore,
+    obligation_cache: &mut ObligationCache,
     pools: &mut Pools,
     aliases: &mut Aliases,
     typ: &Type,
@@ -1958,7 +2117,18 @@ pub(crate) fn type_to_var(
     } else {
         let mut arena = take_scratchpad();
 
-        let var = type_to_variable(subs, rank, pools, &arena, aliases, typ, false);
+        let var = type_to_variable(
+            subs,
+            rank,
+            pools,
+            problems,
+            abilities_store,
+            obligation_cache,
+            &arena,
+            aliases,
+            typ,
+            false,
+        );
 
         arena.reset();
         put_scratchpad(arena);
@@ -2109,6 +2279,9 @@ fn type_to_variable<'a>(
     subs: &mut Subs,
     rank: Rank,
     pools: &mut Pools,
+    problems: &mut Vec<TypeError>,
+    abilities_store: &AbilitiesStore,
+    obligation_cache: &mut ObligationCache,
     arena: &'a bumpalo::Bump,
     aliases: &mut Aliases,
     typ: &Type,
@@ -2118,6 +2291,7 @@ fn type_to_variable<'a>(
     use bumpalo::collections::Vec;
 
     let mut stack = Vec::with_capacity_in(8, arena);
+    let mut bind_to_ability = Vec::new_in(arena);
 
     macro_rules! helper {
         ($typ:expr, $ambient_function_policy:expr) => {{
@@ -2165,7 +2339,7 @@ fn type_to_variable<'a>(
             Apply(symbol, arguments, _) => {
                 let new_arguments = VariableSubsSlice::reserve_into_subs(subs, arguments.len());
                 for (target_index, var_index) in (new_arguments.indices()).zip(arguments) {
-                    let var = helper!(var_index);
+                    let var = helper!(&var_index.value);
                     subs.variables[target_index] = var;
                 }
 
@@ -2356,8 +2530,11 @@ fn type_to_variable<'a>(
                     let new_variables = VariableSubsSlice::reserve_into_subs(subs, length);
 
                     for (target_index, arg_type) in (new_variables.indices()).zip(type_arguments) {
-                        let copy_var = helper!(arg_type);
+                        let copy_var = helper!(&arg_type.value.typ);
                         subs.variables[target_index] = copy_var;
+                        if let Some(ability) = arg_type.value.opt_ability {
+                            bind_to_ability.push((Loc::at(arg_type.region, copy_var), ability));
+                        }
                     }
 
                     let it = (new_variables.indices().skip(type_arguments.len()))
@@ -2365,8 +2542,18 @@ fn type_to_variable<'a>(
                     for (target_index, ls) in it {
                         // We MUST do this now, otherwise when linking the ambient function during
                         // instantiation of the real var, there will be nothing to link against.
-                        let copy_var =
+                        let copy_var = type_to_variable(
-                            type_to_variable(subs, rank, pools, arena, aliases, &ls.0, true);
+                            subs,
+                            rank,
+                            pools,
+                            problems,
+                            abilities_store,
+                            obligation_cache,
+                            arena,
+                            aliases,
+                            &ls.0,
+                            true,
+                        );
                         subs.variables[target_index] = copy_var;
                     }
 
@@ -2381,6 +2568,9 @@ fn type_to_variable<'a>(
                     subs,
                     rank,
                     pools,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
                     arena,
                     *symbol,
                     alias_variables,
@@ -2488,8 +2678,18 @@ fn type_to_variable<'a>(
                     for (target_index, ls) in it {
                         // We MUST do this now, otherwise when linking the ambient function during
                         // instantiation of the real var, there will be nothing to link against.
-                        let copy_var =
+                        let copy_var = type_to_variable(
-                            type_to_variable(subs, rank, pools, arena, aliases, &ls.0, true);
+                            subs,
+                            rank,
+                            pools,
+                            problems,
+                            abilities_store,
+                            obligation_cache,
+                            arena,
+                            aliases,
+                            &ls.0,
+                            true,
+                        );
                         subs.variables[target_index] = copy_var;
                     }
 
@@ -2501,8 +2701,18 @@ fn type_to_variable<'a>(
                 };
 
                 // cannot use helper! here because this variable may be involved in unification below
-                let alias_variable =
+                let alias_variable = type_to_variable(
-                    type_to_variable(subs, rank, pools, arena, aliases, alias_type, false);
+                    subs,
+                    rank,
+                    pools,
+                    problems,
+                    abilities_store,
+                    obligation_cache,
+                    arena,
+                    aliases,
+                    alias_type,
+                    false,
+                );
                 // TODO(opaques): I think host-exposed aliases should always be structural
                 // (when does it make sense to give a host an opaque type?)
                 let content = Content::Alias(
@@ -2533,6 +2743,67 @@ fn type_to_variable<'a>(
         };
     }
 
+    for (Loc { value: var, region }, ability) in bind_to_ability {
+        match *subs.get_content_unchecked(var) {
+            Content::RigidVar(a) => {
+                subs.set_content(var, Content::RigidAbleVar(a, ability));
+            }
+            Content::RigidAbleVar(_, ab) if ab == ability => {
+                // pass, already bound
+            }
+            _ => {
+                let flex_ability = subs.fresh(Descriptor {
+                    content: Content::FlexAbleVar(None, ability),
+                    rank,
+                    mark: Mark::NONE,
+                    copy: OptVariable::NONE,
+                });
+
+                let category = Category::OpaqueArg;
+                match unify(&mut UEnv::new(subs), var, flex_ability, Mode::EQ) {
+                    Success {
+                        vars: _,
+                        must_implement_ability,
+                        lambda_sets_to_specialize,
+                        extra_metadata: _,
+                    } => {
+                        // No introduction needed
+
+                        if !must_implement_ability.is_empty() {
+                            let new_problems = obligation_cache.check_obligations(
+                                subs,
+                                abilities_store,
+                                must_implement_ability,
+                                AbilityImplError::BadExpr(region, category, flex_ability),
+                            );
+                            problems.extend(new_problems);
+                        }
+                        debug_assert!(lambda_sets_to_specialize
+                            .drain()
+                            .all(|(_, vals)| vals.is_empty()));
+                    }
+                    Failure(_vars, actual_type, expected_type, _bad_impls) => {
+                        // No introduction needed
+
+                        let problem = TypeError::BadExpr(
+                            region,
+                            category,
+                            actual_type,
+                            Expected::NoExpectation(expected_type),
+                        );
+
+                        problems.push(problem);
+                    }
+                    BadType(_vars, problem) => {
+                        // No introduction needed
+
+                        problems.push(TypeError::BadType(problem));
+                    }
+                }
+            }
+        }
+    }
+
     result
 }
 

crates/compiler/solve/tests/solve_expr.rs

@@ -7991,4 +7991,22 @@ mod solve_expr {
             "Bool",
         );
     }
+
+    #[test]
+    fn expand_able_variables_in_type_alias() {
+        infer_queries!(
+            indoc!(
+                r#"
+                app "test" provides [main] to "./platform"
+
+                F a : a | a has Hash
+
+                main : F a -> F a
+                #^^^^{-1}
+                "#
+            ),
+            @"main : a -[[main(0)]]-> a | a has Hash"
+            print_only_under_alias: true
+        );
+    }
 }

crates/compiler/types/src/types.rs

@@ -209,7 +209,7 @@ impl LambdaSet {
 #[derive(PartialEq, Eq, Clone)]
 pub struct AliasCommon {
     pub symbol: Symbol,
-    pub type_arguments: Vec<Type>,
+    pub type_arguments: Vec<Loc<OptAbleType>>,
     pub lambda_set_variables: Vec<LambdaSet>,
 }
 
@@ -282,7 +282,7 @@ pub enum Type {
     },
     RecursiveTagUnion(Variable, Vec<(TagName, Vec<Type>)>, TypeExtension),
     /// Applying a type to some arguments (e.g. Dict.Dict String Int)
-    Apply(Symbol, Vec<Type>, Region),
+    Apply(Symbol, Vec<Loc<Type>>, Region),
     Variable(Variable),
     RangedNumber(NumericRange),
     /// A type error, which will code gen to a runtime error
@@ -793,7 +793,7 @@ impl Type {
                     ..
                 }) => {
                     for value in type_arguments.iter_mut() {
-                        stack.push(value);
+                        stack.push(&mut value.value.typ);
                     }
 
                     for lambda_set in lambda_set_variables.iter_mut() {
@@ -833,7 +833,7 @@ impl Type {
                     stack.push(actual_type);
                 }
                 Apply(_, args, _) => {
-                    stack.extend(args);
+                    stack.extend(args.iter_mut().map(|t| &mut t.value));
                 }
                 RangedNumber(_) => {}
                 UnspecializedLambdaSet {
@@ -915,7 +915,7 @@ impl Type {
                     ..
                 }) => {
                     for value in type_arguments.iter_mut() {
-                        stack.push(value);
+                        stack.push(&mut value.value.typ);
                     }
 
                     for lambda_set in lambda_set_variables.iter_mut() {
@@ -954,7 +954,7 @@ impl Type {
                     stack.push(actual_type);
                 }
                 Apply(_, args, _) => {
-                    stack.extend(args);
+                    stack.extend(args.iter_mut().map(|t| &mut t.value));
                 }
                 RangedNumber(_) => {}
                 UnspecializedLambdaSet {
@@ -1021,7 +1021,9 @@ impl Type {
                 ..
             }) => {
                 for ta in type_arguments {
-                    ta.substitute_alias(rep_symbol, rep_args, actual)?;
+                    ta.value
+                        .typ
+                        .substitute_alias(rep_symbol, rep_args, actual)?;
                 }
 
                 Ok(())
@@ -1042,13 +1044,16 @@ impl Type {
             } => actual_type.substitute_alias(rep_symbol, rep_args, actual),
             Apply(symbol, args, region) if *symbol == rep_symbol => {
                 if args.len() == rep_args.len()
-                    && args.iter().zip(rep_args.iter()).all(|(t1, t2)| t1 == t2)
+                    && args
+                        .iter()
+                        .zip(rep_args.iter())
+                        .all(|(t1, t2)| &t1.value == t2)
                 {
                     *self = actual.clone();
 
                     if let Apply(_, args, _) = self {
                         for arg in args {
-                            arg.substitute_alias(rep_symbol, rep_args, actual)?;
+                            arg.value.substitute_alias(rep_symbol, rep_args, actual)?;
                         }
                     }
                     return Ok(());
@@ -1057,7 +1062,7 @@ impl Type {
             }
             Apply(_, args, _) => {
                 for arg in args {
-                    arg.substitute_alias(rep_symbol, rep_args, actual)?;
+                    arg.value.substitute_alias(rep_symbol, rep_args, actual)?;
                 }
                 Ok(())
             }
@@ -1103,7 +1108,9 @@ impl Type {
                 ..
             }) => {
                 symbol == &rep_symbol
-                    || type_arguments.iter().any(|v| v.contains_symbol(rep_symbol))
+                    || type_arguments
+                        .iter()
+                        .any(|v| v.value.typ.contains_symbol(rep_symbol))
                     || lambda_set_variables
                         .iter()
                         .any(|v| v.0.contains_symbol(rep_symbol))
@@ -1117,7 +1124,7 @@ impl Type {
                 name == &rep_symbol || actual.contains_symbol(rep_symbol)
             }
             Apply(symbol, _, _) if *symbol == rep_symbol => true,
-            Apply(_, args, _) => args.iter().any(|arg| arg.contains_symbol(rep_symbol)),
+            Apply(_, args, _) => args.iter().any(|arg| arg.value.contains_symbol(rep_symbol)),
             RangedNumber(_) => false,
             UnspecializedLambdaSet {
                 unspecialized: Uls(_, sym, _),
@@ -1174,7 +1181,9 @@ impl Type {
                 ..
             } => actual_type.contains_variable(rep_variable),
             HostExposedAlias { actual, .. } => actual.contains_variable(rep_variable),
-            Apply(_, args, _) => args.iter().any(|arg| arg.contains_variable(rep_variable)),
+            Apply(_, args, _) => args
+                .iter()
+                .any(|arg| arg.value.contains_variable(rep_variable)),
             RangedNumber(_) => false,
             EmptyRec | EmptyTagUnion | Erroneous(_) => false,
         }
@@ -1259,7 +1268,12 @@ impl Type {
                     .iter()
                     .all(|lambda_set| matches!(lambda_set.0, Type::Variable(..))));
                 type_arguments.iter_mut().for_each(|t| {
-                    t.instantiate_aliases(region, aliases, var_store, new_lambda_set_variables)
+                    t.value.typ.instantiate_aliases(
+                        region,
+                        aliases,
+                        var_store,
+                        new_lambda_set_variables,
+                    )
                 });
             }
             HostExposedAlias {
@@ -1316,8 +1330,14 @@ impl Type {
                     if false {
                         let mut type_var_to_arg = Vec::new();
 
-                        for (_, arg_ann) in alias.type_variables.iter().zip(args) {
+                        for (alias_var, arg_ann) in alias.type_variables.iter().zip(args) {
-                            type_var_to_arg.push(arg_ann.clone());
+                            type_var_to_arg.push(Loc::at(
+                                arg_ann.region,
+                                OptAbleType {
+                                    typ: arg_ann.value.clone(),
+                                    opt_ability: alias_var.value.opt_bound_ability,
+                                },
+                            ));
                         }
 
                         let mut lambda_set_variables =
@@ -1370,17 +1390,17 @@ impl Type {
                         ) in alias.type_variables.iter().zip(args.iter())
                         {
                             let mut filler = filler.clone();
-                            filler.instantiate_aliases(
+                            filler.value.instantiate_aliases(
                                 region,
                                 aliases,
                                 var_store,
                                 new_lambda_set_variables,
                             );
                             named_args.push(OptAbleType {
-                                typ: filler.clone(),
+                                typ: filler.value.clone(),
                                 opt_ability: *opt_bound_ability,
                             });
-                            substitution.insert(*placeholder, filler);
+                            substitution.insert(*placeholder, filler.value);
                         }
 
                         // make sure hidden variables are freshly instantiated
@@ -1435,7 +1455,12 @@ impl Type {
                 } else {
                     // one of the special-cased Apply types.
                     for x in args {
-                        x.instantiate_aliases(region, aliases, var_store, new_lambda_set_variables);
+                        x.value.instantiate_aliases(
+                            region,
+                            aliases,
+                            var_store,
+                            new_lambda_set_variables,
+                        );
                     }
                 }
             }
@@ -1552,7 +1577,7 @@ fn symbols_help(initial: &Type) -> Vec<Symbol> {
                 ..
             }) => {
                 output.push(*symbol);
-                stack.extend(type_arguments);
+                stack.extend(type_arguments.iter().map(|ta| &ta.value.typ));
             }
             Alias {
                 symbol: alias_symbol,
@@ -1572,7 +1597,7 @@ fn symbols_help(initial: &Type) -> Vec<Symbol> {
             }
             Apply(symbol, args, _) => {
                 output.push(*symbol);
-                stack.extend(args);
+                stack.extend(args.iter().map(|t| &t.value));
             }
             Erroneous(Problem::CyclicAlias(alias, _, _)) => {
                 output.push(*alias);
@@ -1679,7 +1704,7 @@ fn variables_help(tipe: &Type, accum: &mut ImSet<Variable>) {
             ..
         }) => {
             for arg in type_arguments {
-                variables_help(arg, accum);
+                variables_help(&arg.value.typ, accum);
             }
 
             for lambda_set in lambda_set_variables {
@@ -1709,7 +1734,7 @@ fn variables_help(tipe: &Type, accum: &mut ImSet<Variable>) {
         RangedNumber(_) => {}
         Apply(_, args, _) => {
             for x in args {
-                variables_help(x, accum);
+                variables_help(&x.value, accum);
             }
         }
     }
@@ -1823,7 +1848,7 @@ fn variables_help_detailed(tipe: &Type, accum: &mut VariableDetail) {
             ..
         }) => {
             for arg in type_arguments {
-                variables_help_detailed(arg, accum);
+                variables_help_detailed(&arg.value.typ, accum);
             }
 
             for lambda_set in lambda_set_variables {
@@ -1857,7 +1882,7 @@ fn variables_help_detailed(tipe: &Type, accum: &mut VariableDetail) {
         RangedNumber(_) => {}
         Apply(_, args, _) => {
             for x in args {
-                variables_help_detailed(x, accum);
+                variables_help_detailed(&x.value, accum);
             }
         }
     }
@@ -2928,7 +2953,7 @@ fn instantiate_lambda_sets_as_unspecialized(
                     debug_assert!(matches!(lambda_set.0, Type::Variable(_)));
                     lambda_set.0 = new_uls();
                 }
-                stack.extend(type_arguments.iter_mut().rev());
+                stack.extend(type_arguments.iter_mut().rev().map(|ta| &mut ta.value.typ));
             }
             Type::Alias {
                 symbol: _,
@@ -2959,7 +2984,7 @@ fn instantiate_lambda_sets_as_unspecialized(
                 stack.extend(type_arguments.iter_mut().rev());
             }
             Type::Apply(_sym, args, _region) => {
-                stack.extend(args.iter_mut().rev());
+                stack.extend(args.iter_mut().rev().map(|t| &mut t.value));
             }
             Type::Variable(_) => {}
             Type::RangedNumber(_) => {}

crates/reporting/tests/test_reporting.rs

@@ -11430,4 +11430,31 @@ All branches in an `if` must have the same type!
         Bool.false
     "###
     );
+
+    test_report!(
+        expand_ability_from_type_alias_mismatch,
+        indoc!(
+            r#"
+            app "test" provides [f] to "./platform"
+
+            F a : a | a has Hash
+
+            f : F ({} -> {})
+            "#
+        ),
+    @r###"
+    ── TYPE MISMATCH ───────────────────────────────────────── /code/proj/Main.roc ─
+
+    This expression has a type that does not implement the abilities it's expected to:
+
+    5│  f : F ({} -> {})
+               ^^^^^^^^
+
+    I can't generate an implementation of the `Hash` ability for
+
+        {} -> {}
+
+    Note: `Hash` cannot be generated for functions.
+    "###
+    );
 }