Parse has-derived clauses

compiler/parse/src/ast.rs

@@ -297,6 +297,7 @@ pub enum TypeDef<'a> {
     Opaque {
         header: TypeHeader<'a>,
         typ: Loc<TypeAnnotation<'a>>,
+        derived: Option<Loc<Derived<'a>>>,
     },
 
     /// An ability definition. E.g.
@@ -380,11 +381,23 @@ impl<'a> From<ValueDef<'a>> for Def<'a> {
     }
 }
 
+/// Should always be a zero-argument `Apply`; we'll check this in canonicalization
+pub type AbilityName<'a> = Loc<TypeAnnotation<'a>>;
+
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub struct HasClause<'a> {
     pub var: Loc<Spaced<'a, &'a str>>,
-    // Should always be a zero-argument `Apply`; we'll check this in canonicalization
+    pub ability: AbilityName<'a>,
-    pub ability: Loc<TypeAnnotation<'a>>,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub enum Derived<'a> {
+    /// `has [ Eq, Hash ]`
+    Has(Collection<'a, AbilityName<'a>>),
+
+    // We preserve this for the formatter; canonicalization ignores it.
+    SpaceBefore(&'a Derived<'a>, &'a [CommentOrNewline<'a>]),
+    SpaceAfter(&'a Derived<'a>, &'a [CommentOrNewline<'a>]),
 }
 
 #[derive(Debug, Copy, Clone, PartialEq)]
@@ -901,6 +914,15 @@ impl<'a> Spaceable<'a> for Has<'a> {
     }
 }
 
+impl<'a> Spaceable<'a> for Derived<'a> {
+    fn before(&'a self, spaces: &'a [CommentOrNewline<'a>]) -> Self {
+        Derived::SpaceBefore(self, spaces)
+    }
+    fn after(&'a self, spaces: &'a [CommentOrNewline<'a>]) -> Self {
+        Derived::SpaceAfter(self, spaces)
+    }
+}
+
 impl<'a> Expr<'a> {
     pub fn loc_ref(&'a self, region: Region) -> Loc<&'a Self> {
         Loc {

compiler/parse/src/expr.rs

@@ -1,6 +1,6 @@
 use crate::ast::{
-    AssignedField, Collection, CommentOrNewline, Def, Expr, ExtractSpaces, Has, Pattern, Spaceable,
+    AssignedField, Collection, CommentOrNewline, Def, Derived, Expr, ExtractSpaces, Has, Pattern,
-    TypeAnnotation, TypeDef, TypeHeader, ValueDef,
+    Spaceable, TypeAnnotation, TypeDef, TypeHeader, ValueDef,
 };
 use crate::blankspace::{
     space0_after_e, space0_around_ee, space0_before_e, space0_before_optional_after, space0_e,
@@ -426,21 +426,21 @@ impl<'a> ExprState<'a> {
         mut self,
         arena: &'a Bump,
         loc_op: Loc<BinOp>,
-        kind: TypeKind,
+        kind: AliasOrOpaque,
     ) -> Result<(Loc<Expr<'a>>, Vec<'a, &'a Loc<Expr<'a>>>), EExpr<'a>> {
         debug_assert_eq!(
             loc_op.value,
             match kind {
-                TypeKind::Alias => BinOp::IsAliasType,
+                AliasOrOpaque::Alias => BinOp::IsAliasType,
-                TypeKind::Opaque => BinOp::IsOpaqueType,
+                AliasOrOpaque::Opaque => BinOp::IsOpaqueType,
             }
         );
 
         if !self.operators.is_empty() {
             // this `:`/`:=` likely occurred inline; treat it as an invalid operator
             let op = match kind {
-                TypeKind::Alias => ":",
+                AliasOrOpaque::Alias => ":",
-                TypeKind::Opaque => ":=",
+                AliasOrOpaque::Opaque => ":=",
             };
             let fail = EExpr::BadOperator(op, loc_op.region.start());
 
@@ -690,7 +690,10 @@ fn append_annotation_definition<'a>(
     spaces: &'a [CommentOrNewline<'a>],
     loc_pattern: Loc<Pattern<'a>>,
     loc_ann: Loc<TypeAnnotation<'a>>,
-    kind: TypeKind,
+
+    // If this turns out to be an alias
+    kind: AliasOrOpaque,
+    opt_derived: Option<Loc<Derived<'a>>>,
 ) {
     let region = Region::span_across(&loc_pattern.region, &loc_ann.region);
 
@@ -702,7 +705,7 @@ fn append_annotation_definition<'a>(
                 ..
             },
             alias_arguments,
-        ) => append_type_definition(
+        ) => append_alias_or_opaque_definition(
             arena,
             defs,
             region,
@@ -711,8 +714,9 @@ fn append_annotation_definition<'a>(
             alias_arguments,
             loc_ann,
             kind,
+            opt_derived,
         ),
-        Pattern::Tag(name) => append_type_definition(
+        Pattern::Tag(name) => append_alias_or_opaque_definition(
             arena,
             defs,
             region,
@@ -721,6 +725,7 @@ fn append_annotation_definition<'a>(
             &[],
             loc_ann,
             kind,
+            opt_derived,
         ),
         _ => {
             let mut loc_def = Loc::at(
@@ -762,7 +767,7 @@ fn append_expect_definition<'a>(
 }
 
 #[allow(clippy::too_many_arguments)]
-fn append_type_definition<'a>(
+fn append_alias_or_opaque_definition<'a>(
     arena: &'a Bump,
     defs: &mut Vec<'a, &'a Loc<Def<'a>>>,
     region: Region,
@@ -770,23 +775,26 @@ fn append_type_definition<'a>(
     name: Loc<&'a str>,
     pattern_arguments: &'a [Loc<Pattern<'a>>],
     loc_ann: Loc<TypeAnnotation<'a>>,
-    kind: TypeKind,
+    kind: AliasOrOpaque,
+    opt_derived: Option<Loc<Derived<'a>>>,
 ) {
     let header = TypeHeader {
         name,
         vars: pattern_arguments,
     };
-    let def = match kind {
+
-        TypeKind::Alias => TypeDef::Alias {
+    let type_def = match kind {
+        AliasOrOpaque::Alias => TypeDef::Alias {
             header,
             ann: loc_ann,
         },
-        TypeKind::Opaque => TypeDef::Opaque {
+        AliasOrOpaque::Opaque => TypeDef::Opaque {
             header,
             typ: loc_ann,
+            derived: opt_derived,
         },
     };
-    let mut loc_def = Loc::at(region, Def::Type(def));
+    let mut loc_def = Loc::at(region, Def::Type(type_def));
 
     if !spaces.is_empty() {
         loc_def = arena
@@ -922,16 +930,9 @@ fn parse_defs_end<'a>(
 
                     parse_defs_end(options, column, def_state, arena, state)
                 }
-                Ok((_, op @ (BinOp::IsAliasType | BinOp::IsOpaqueType), state)) => {
+                Ok((_, BinOp::IsAliasType, state)) => {
-                    let (_, ann_type, state) = specialize(
+                    let (_, ann_type, state) =
-                        EExpr::Type,
+                        alias_signature_with_space_before(min_indent + 1).parse(arena, state)?;
-                        space0_before_e(
-                            type_annotation::located_help(min_indent + 1, false),
-                            min_indent + 1,
-                            EType::TIndentStart,
-                        ),
-                    )
-                    .parse(arena, state)?;
 
                     append_annotation_definition(
                         arena,
@@ -939,11 +940,24 @@ fn parse_defs_end<'a>(
                         def_state.spaces_after,
                         loc_pattern,
                         ann_type,
-                        match op {
+                        AliasOrOpaque::Alias,
-                            BinOp::IsAliasType => TypeKind::Alias,
+                        None,
-                            BinOp::IsOpaqueType => TypeKind::Opaque,
+                    );
-                            _ => unreachable!(),
+
-                        },
+                    parse_defs_end(options, column, def_state, arena, state)
+                }
+                Ok((_, BinOp::IsOpaqueType, state)) => {
+                    let (_, (signature, derived), state) =
+                        opaque_signature_with_space_before(min_indent + 1).parse(arena, state)?;
+
+                    append_annotation_definition(
+                        arena,
+                        &mut def_state.defs,
+                        def_state.spaces_after,
+                        loc_pattern,
+                        signature,
+                        AliasOrOpaque::Opaque,
+                        derived,
                     );
 
                     parse_defs_end(options, column, def_state, arena, state)
@@ -994,8 +1008,44 @@ fn parse_defs_expr<'a>(
     }
 }
 
+fn alias_signature_with_space_before<'a>(
+    min_indent: u32,
+) -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EExpr<'a>> {
+    specialize(
+        EExpr::Type,
+        space0_before_e(
+            type_annotation::located(min_indent + 1, false),
+            min_indent + 1,
+            EType::TIndentStart,
+        ),
+    )
+}
+
+fn opaque_signature_with_space_before<'a>(
+    min_indent: u32,
+) -> impl Parser<'a, (Loc<TypeAnnotation<'a>>, Option<Loc<Derived<'a>>>), EExpr<'a>> {
+    and!(
+        specialize(
+            EExpr::Type,
+            space0_before_e(
+                type_annotation::located_opaque_signature(min_indent, true),
+                min_indent,
+                EType::TIndentStart,
+            ),
+        ),
+        optional(specialize(
+            EExpr::Type,
+            space0_before_e(
+                type_annotation::has_derived(min_indent),
+                min_indent,
+                EType::TIndentStart,
+            ),
+        ))
+    )
+}
+
 #[derive(Copy, Clone, PartialEq, Eq)]
-enum TypeKind {
+enum AliasOrOpaque {
     Alias,
     Opaque,
 }
@@ -1010,7 +1060,7 @@ fn finish_parsing_alias_or_opaque<'a>(
     arena: &'a Bump,
     state: State<'a>,
     spaces_after_operator: &'a [CommentOrNewline<'a>],
-    kind: TypeKind,
+    kind: AliasOrOpaque,
 ) -> ParseResult<'a, Expr<'a>, EExpr<'a>> {
     let expr_region = expr_state.expr.region;
     let indented_more = start_column + 1;
@@ -1032,34 +1082,48 @@ fn finish_parsing_alias_or_opaque<'a>(
                 }
             }
 
-            let (_, ann_type, state) = specialize(
+            let (loc_def, state) = match kind {
-                EExpr::Type,
+                AliasOrOpaque::Alias => {
-                space0_before_e(
+                    let (_, signature, state) =
-                    type_annotation::located_help(indented_more, true),
+                        alias_signature_with_space_before(indented_more).parse(arena, state)?;
-                    min_indent,
-                    EType::TIndentStart,
-                ),
-            )
-            .parse(arena, state)?;
 
-            let def_region = Region::span_across(&expr.region, &ann_type.region);
+                    let def_region = Region::span_across(&expr.region, &signature.region);
 
                     let header = TypeHeader {
                         name: Loc::at(expr.region, name),
                         vars: type_arguments.into_bump_slice(),
                     };
-            let type_def = match kind {
+
-                TypeKind::Alias => TypeDef::Alias {
+                    let def = TypeDef::Alias {
                         header,
-                    ann: ann_type,
+                        ann: signature,
-                },
-                TypeKind::Opaque => TypeDef::Opaque {
-                    header,
-                    typ: ann_type,
-                },
                     };
 
-            (&*arena.alloc(Loc::at(def_region, type_def.into())), state)
+                    (Loc::at(def_region, Def::Type(def)), state)
+                }
+
+                AliasOrOpaque::Opaque => {
+                    let (_, (signature, derived), state) =
+                        opaque_signature_with_space_before(indented_more).parse(arena, state)?;
+
+                    let def_region = Region::span_across(&expr.region, &signature.region);
+
+                    let header = TypeHeader {
+                        name: Loc::at(expr.region, name),
+                        vars: type_arguments.into_bump_slice(),
+                    };
+
+                    let def = TypeDef::Opaque {
+                        header,
+                        typ: signature,
+                        derived,
+                    };
+
+                    (Loc::at(def_region, Def::Type(def)), state)
+                }
+            };
+
+            (&*arena.alloc(loc_def), state)
         }
 
         _ => {
@@ -1070,7 +1134,7 @@ fn finish_parsing_alias_or_opaque<'a>(
                     let parser = specialize(
                         EExpr::Type,
                         space0_before_e(
-                            type_annotation::located_help(indented_more, false),
+                            type_annotation::located(indented_more, false),
                             min_indent,
                             EType::TIndentStart,
                         ),
@@ -1097,8 +1161,8 @@ fn finish_parsing_alias_or_opaque<'a>(
                 Err(_) => {
                     // this `:`/`:=` likely occurred inline; treat it as an invalid operator
                     let op = match kind {
-                        TypeKind::Alias => ":",
+                        AliasOrOpaque::Alias => ":",
-                        TypeKind::Opaque => ":=",
+                        AliasOrOpaque::Opaque => ":=",
                     };
                     let fail = EExpr::BadOperator(op, loc_op.region.start());
 
@@ -1139,7 +1203,7 @@ mod ability {
                     specialize(
                         EAbility::Type,
                         // Require the type to be more indented than the name
-                        type_annotation::located_help(start_column + 1, true)
+                        type_annotation::located(start_column + 1, true)
                     )
                 )
             ),
@@ -1463,8 +1527,8 @@ fn parse_expr_operator<'a>(
             state,
             spaces_after_operator,
             match op {
-                BinOp::IsAliasType => TypeKind::Alias,
+                BinOp::IsAliasType => AliasOrOpaque::Alias,
-                BinOp::IsOpaqueType => TypeKind::Opaque,
+                BinOp::IsOpaqueType => AliasOrOpaque::Opaque,
                 _ => unreachable!(),
             },
         ),

compiler/parse/src/module.rs

@@ -816,7 +816,7 @@ fn typed_ident<'a>() -> impl Parser<'a, Spaced<'a, TypedIdent<'a>>, ETypedIdent<
                 space0_before_e(
                     specialize(
                         ETypedIdent::Type,
-                        type_annotation::located_help(min_indent, true)
+                        type_annotation::located(min_indent, true)
                     ),
                     min_indent,
                     ETypedIdent::IndentType,

compiler/parse/src/type_annotation.rs

@@ -1,5 +1,6 @@
 use crate::ast::{
-    AssignedField, CommentOrNewline, HasClause, Pattern, Spaced, Tag, TypeAnnotation, TypeHeader,
+    AssignedField, CommentOrNewline, Derived, HasClause, Pattern, Spaced, Tag, TypeAnnotation,
+    TypeHeader,
 };
 use crate::blankspace::{space0_around_ee, space0_before_e, space0_e};
 use crate::ident::lowercase_ident;
@@ -15,19 +16,29 @@ use bumpalo::collections::vec::Vec;
 use bumpalo::Bump;
 use roc_region::all::{Loc, Position, Region};
 
-pub fn located_help<'a>(
+pub fn located<'a>(
     min_indent: u32,
     is_trailing_comma_valid: bool,
 ) -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EType<'a>> {
-    expression(min_indent, is_trailing_comma_valid)
+    expression(min_indent, is_trailing_comma_valid, false)
+}
+
+pub fn located_opaque_signature<'a>(
+    min_indent: u32,
+    is_trailing_comma_valid: bool,
+) -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EType<'a>> {
+    expression(min_indent, is_trailing_comma_valid, true)
 }
 
 #[inline(always)]
-fn tag_union_type<'a>(min_indent: u32) -> impl Parser<'a, TypeAnnotation<'a>, ETypeTagUnion<'a>> {
+fn tag_union_type<'a>(
+    min_indent: u32,
+    stop_at_surface_has: bool,
+) -> impl Parser<'a, TypeAnnotation<'a>, ETypeTagUnion<'a>> {
     move |arena, state| {
         let (_, tags, state) = collection_trailing_sep_e!(
             word1(b'[', ETypeTagUnion::Open),
-            loc!(tag_type(min_indent)),
+            loc!(tag_type(min_indent, false)),
             word1(b',', ETypeTagUnion::End),
             word1(b']', ETypeTagUnion::End),
             min_indent,
@@ -40,7 +51,7 @@ fn tag_union_type<'a>(min_indent: u32) -> impl Parser<'a, TypeAnnotation<'a>, ET
         // This could be an open tag union, e.g. `[ Foo, Bar ]a`
         let (_, ext, state) = optional(allocated(specialize_ref(
             ETypeTagUnion::Type,
-            term(min_indent),
+            term(min_indent, stop_at_surface_has),
         )))
         .parse(arena, state)?;
 
@@ -90,7 +101,7 @@ fn check_type_alias(
 
 fn parse_type_alias_after_as<'a>(min_indent: u32) -> impl Parser<'a, TypeHeader<'a>, EType<'a>> {
     move |arena, state| {
-        space0_before_e(term(min_indent), min_indent, EType::TAsIndentStart)
+        space0_before_e(term(min_indent, false), min_indent, EType::TAsIndentStart)
             .parse(arena, state)
             .and_then(|(p, annot, state)| {
                 specialize(EType::TInlineAlias, check_type_alias(p, annot)).parse(arena, state)
@@ -102,17 +113,26 @@ fn fail_type_start<'a, T: 'a>() -> impl Parser<'a, T, EType<'a>> {
     |_arena, state: State<'a>| Err((NoProgress, EType::TStart(state.pos()), state))
 }
 
-fn term<'a>(min_indent: u32) -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EType<'a>> {
+fn term<'a>(
+    min_indent: u32,
+    stop_at_surface_has: bool,
+) -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EType<'a>> {
     map_with_arena!(
         and!(
             one_of!(
                 loc_wildcard(),
                 loc_inferred(),
                 specialize(EType::TInParens, loc_type_in_parens(min_indent)),
-                loc!(specialize(EType::TRecord, record_type(min_indent))),
+                loc!(specialize(
-                loc!(specialize(EType::TTagUnion, tag_union_type(min_indent))),
+                    EType::TRecord,
-                loc!(applied_type(min_indent)),
+                    record_type(min_indent, stop_at_surface_has)
-                loc!(parse_type_variable),
+                )),
+                loc!(specialize(
+                    EType::TTagUnion,
+                    tag_union_type(min_indent, stop_at_surface_has)
+                )),
+                loc!(applied_type(min_indent, stop_at_surface_has)),
+                loc!(parse_type_variable(stop_at_surface_has)),
                 fail_type_start(),
             ),
             // Inline alias notation, e.g. [ Nil, Cons a (List a) ] as List a
@@ -163,7 +183,10 @@ fn loc_inferred<'a>() -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EType<'a>> {
     })
 }
 
-fn loc_applied_arg<'a>(min_indent: u32) -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EType<'a>> {
+fn loc_applied_arg<'a>(
+    min_indent: u32,
+    stop_at_surface_has: bool,
+) -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EType<'a>> {
     use crate::ast::Spaceable;
 
     map_with_arena!(
@@ -173,10 +196,16 @@ fn loc_applied_arg<'a>(min_indent: u32) -> impl Parser<'a, Loc<TypeAnnotation<'a
                 loc_wildcard(),
                 loc_inferred(),
                 specialize(EType::TInParens, loc_type_in_parens(min_indent)),
-                loc!(specialize(EType::TRecord, record_type(min_indent))),
+                loc!(specialize(
-                loc!(specialize(EType::TTagUnion, tag_union_type(min_indent))),
+                    EType::TRecord,
+                    record_type(min_indent, stop_at_surface_has)
+                )),
+                loc!(specialize(
+                    EType::TTagUnion,
+                    tag_union_type(min_indent, stop_at_surface_has)
+                )),
                 loc!(specialize(EType::TApply, parse_concrete_type)),
-                loc!(parse_type_variable)
+                loc!(parse_type_variable(stop_at_surface_has))
             )
         ),
         |arena: &'a Bump, (spaces, argument): (&'a [_], Loc<TypeAnnotation<'a>>)| {
@@ -196,7 +225,10 @@ fn loc_type_in_parens<'a>(
     between!(
         word1(b'(', ETypeInParens::Open),
         space0_around_ee(
-            move |arena, state| specialize_ref(ETypeInParens::Type, expression(min_indent, true))
+            move |arena, state| specialize_ref(
+                ETypeInParens::Type,
+                expression(min_indent, true, false)
+            )
             .parse(arena, state),
             min_indent,
             ETypeInParens::IndentOpen,
@@ -207,11 +239,17 @@ fn loc_type_in_parens<'a>(
 }
 
 #[inline(always)]
-fn tag_type<'a>(min_indent: u32) -> impl Parser<'a, Tag<'a>, ETypeTagUnion<'a>> {
+fn tag_type<'a>(
+    min_indent: u32,
+    stop_at_surface_has: bool,
+) -> impl Parser<'a, Tag<'a>, ETypeTagUnion<'a>> {
     move |arena, state: State<'a>| {
         let (_, name, state) = loc!(parse_tag_name(ETypeTagUnion::End)).parse(arena, state)?;
 
-        let (_, args, state) = specialize_ref(ETypeTagUnion::Type, loc_applied_args_e(min_indent))
+        let (_, args, state) = specialize_ref(
+            ETypeTagUnion::Type,
+            loc_applied_args_e(min_indent, stop_at_surface_has),
+        )
         .parse(arena, state)?;
 
         let result = Tag::Apply {
@@ -262,7 +300,7 @@ fn record_type_field<'a>(
         ))
         .parse(arena, state)?;
 
-        let val_parser = specialize_ref(ETypeRecord::Type, expression(min_indent, true));
+        let val_parser = specialize_ref(ETypeRecord::Type, expression(min_indent, true, false));
 
         match opt_loc_val {
             Some(First(_)) => {
@@ -304,7 +342,10 @@ fn record_type_field<'a>(
 }
 
 #[inline(always)]
-fn record_type<'a>(min_indent: u32) -> impl Parser<'a, TypeAnnotation<'a>, ETypeRecord<'a>> {
+fn record_type<'a>(
+    min_indent: u32,
+    stop_at_surface_has: bool,
+) -> impl Parser<'a, TypeAnnotation<'a>, ETypeRecord<'a>> {
     use crate::type_annotation::TypeAnnotation::*;
 
     (move |arena, state| {
@@ -322,7 +363,7 @@ fn record_type<'a>(min_indent: u32) -> impl Parser<'a, TypeAnnotation<'a>, EType
         )
         .parse(arena, state)?;
 
-        let field_term = specialize_ref(ETypeRecord::Type, term(min_indent));
+        let field_term = specialize_ref(ETypeRecord::Type, term(min_indent, stop_at_surface_has));
         let (_, ext, state) = optional(allocated(field_term)).parse(arena, state)?;
 
         let result = Record { fields, ext };
@@ -332,13 +373,16 @@ fn record_type<'a>(min_indent: u32) -> impl Parser<'a, TypeAnnotation<'a>, EType
     .trace("type_annotation:record_type")
 }
 
-fn applied_type<'a>(min_indent: u32) -> impl Parser<'a, TypeAnnotation<'a>, EType<'a>> {
+fn applied_type<'a>(
+    min_indent: u32,
+    stop_at_surface_has: bool,
+) -> impl Parser<'a, TypeAnnotation<'a>, EType<'a>> {
     map!(
         and!(
             specialize(EType::TApply, parse_concrete_type),
             // Optionally parse space-separated arguments for the constructor,
             // e.g. `Str Float` in `Map Str Float`
-            loc_applied_args_e(min_indent)
+            loc_applied_args_e(min_indent, stop_at_surface_has)
         ),
         |(ctor, args): (TypeAnnotation<'a>, Vec<'a, Loc<TypeAnnotation<'a>>>)| {
             match &ctor {
@@ -360,8 +404,9 @@ fn applied_type<'a>(min_indent: u32) -> impl Parser<'a, TypeAnnotation<'a>, ETyp
 
 fn loc_applied_args_e<'a>(
     min_indent: u32,
+    stop_at_surface_has: bool,
 ) -> impl Parser<'a, Vec<'a, Loc<TypeAnnotation<'a>>>, EType<'a>> {
-    zero_or_more!(loc_applied_arg(min_indent))
+    zero_or_more!(loc_applied_arg(min_indent, stop_at_surface_has))
 }
 
 fn has_clause<'a>(min_indent: u32) -> impl Parser<'a, Loc<HasClause<'a>>, EType<'a>> {
@@ -433,12 +478,43 @@ fn has_clause_chain<'a>(
     }
 }
 
+/// Parse a has-derived clause, e.g. `has [ Eq, Hash ]`.
+pub fn has_derived<'a>(min_indent: u32) -> impl Parser<'a, Loc<Derived<'a>>, EType<'a>> {
+    skip_first!(
+        // Parse "has"; we don't care about this keyword
+        word3(b'h', b'a', b's', EType::THasClause),
+        // Parse "Hash"; this may be qualified from another module like "Hash.Hash"
+        space0_before_e(
+            loc!(map!(
+                collection_trailing_sep_e!(
+                    word1(b'[', EType::TStart),
+                    specialize(EType::TApply, loc!(parse_concrete_type)),
+                    word1(b',', EType::TEnd),
+                    word1(b']', EType::TEnd),
+                    min_indent + 1,
+                    EType::TStart,
+                    EType::TIndentEnd,
+                    TypeAnnotation::SpaceBefore
+                ),
+                Derived::Has
+            )),
+            min_indent + 1,
+            EType::TIndentEnd
+        )
+    )
+}
+
 fn expression<'a>(
     min_indent: u32,
     is_trailing_comma_valid: bool,
+    stop_at_surface_has: bool,
 ) -> impl Parser<'a, Loc<TypeAnnotation<'a>>, EType<'a>> {
     (move |arena, state: State<'a>| {
-        let (p1, first, state) = space0_before_e(term(min_indent), min_indent, EType::TIndentStart)
+        let (p1, first, state) = space0_before_e(
+            term(min_indent, stop_at_surface_has),
+            min_indent,
+            EType::TIndentStart,
+        )
         .parse(arena, state)?;
 
         let result = and![
@@ -446,7 +522,7 @@ fn expression<'a>(
                 word1(b',', EType::TFunctionArgument),
                 one_of![
                     space0_around_ee(
-                        term(min_indent),
+                        term(min_indent, stop_at_surface_has),
                         min_indent,
                         EType::TIndentStart,
                         EType::TIndentEnd
@@ -471,8 +547,11 @@ fn expression<'a>(
 
         let (progress, annot, state) = match result {
             Ok((p2, (rest, _dropped_spaces), state)) => {
-                let (p3, return_type, state) =
+                let (p3, return_type, state) = space0_before_e(
-                    space0_before_e(term(min_indent), min_indent, EType::TIndentStart)
+                    term(min_indent, stop_at_surface_has),
+                    min_indent,
+                    EType::TIndentStart,
+                )
                 .parse(arena, state)?;
 
                 let region = Region::span_across(&first.region, &return_type.region);
@@ -590,15 +669,18 @@ fn parse_concrete_type<'a>(
 }
 
 fn parse_type_variable<'a>(
-    arena: &'a Bump,
+    stop_at_surface_has: bool,
-    state: State<'a>,
+) -> impl Parser<'a, TypeAnnotation<'a>, EType<'a>> {
-) -> ParseResult<'a, TypeAnnotation<'a>, EType<'a>> {
+    move |arena, state: State<'a>| match crate::ident::lowercase_ident().parse(arena, state) {
-    match crate::ident::lowercase_ident().parse(arena, state) {
         Ok((_, name, state)) => {
+            if name == "has" && stop_at_surface_has {
+                Err((NoProgress, EType::TEnd(state.pos()), state))
+            } else {
                 let answer = TypeAnnotation::BoundVariable(name);
 
                 Ok((MadeProgress, answer, state))
             }
+        }
         Err((progress, _, state)) => Err((progress, EType::TBadTypeVariable(state.pos()), state)),
     }
 }

compiler/parse/tests/snapshots/pass/opaque_has_abilities.expr.result-ast

@@ -0,0 +1,137 @@
+Defs(
+    [
+        @0-7 Type(
+            Opaque {
+                header: TypeHeader {
+                    name: @0-1 "A",
+                    vars: [],
+                },
+                typ: @5-7 Apply(
+                    "",
+                    "U8",
+                    [],
+                ),
+                derived: Some(
+                    @12-22 Has(
+                        [
+                            @13-15 Apply(
+                                "",
+                                "Eq",
+                                [],
+                            ),
+                            @17-21 Apply(
+                                "",
+                                "Hash",
+                                [],
+                            ),
+                        ],
+                    ),
+                ),
+            },
+        ),
+        @24-44 SpaceBefore(
+            Type(
+                Opaque {
+                    header: TypeHeader {
+                        name: @24-25 "A",
+                        vars: [],
+                    },
+                    typ: @29-44 Where(
+                        @29-30 BoundVariable(
+                            "a",
+                        ),
+                        [
+                            @33-44 HasClause {
+                                var: @33-34 "a",
+                                ability: @39-44 Apply(
+                                    "",
+                                    "Other",
+                                    [],
+                                ),
+                            },
+                        ],
+                    ),
+                    derived: Some(
+                        @49-59 Has(
+                            [
+                                @50-52 Apply(
+                                    "",
+                                    "Eq",
+                                    [],
+                                ),
+                                @54-58 Apply(
+                                    "",
+                                    "Hash",
+                                    [],
+                                ),
+                            ],
+                        ),
+                    ),
+                },
+            ),
+            [
+                Newline,
+                Newline,
+            ],
+        ),
+        @61-81 SpaceBefore(
+            Type(
+                Opaque {
+                    header: TypeHeader {
+                        name: @61-62 "A",
+                        vars: [],
+                    },
+                    typ: @66-81 Where(
+                        @66-67 BoundVariable(
+                            "a",
+                        ),
+                        [
+                            @70-81 HasClause {
+                                var: @70-71 "a",
+                                ability: @76-81 Apply(
+                                    "",
+                                    "Other",
+                                    [],
+                                ),
+                            },
+                        ],
+                    ),
+                    derived: Some(
+                        @91-101 SpaceBefore(
+                            Has(
+                                [
+                                    @92-94 Apply(
+                                        "",
+                                        "Eq",
+                                        [],
+                                    ),
+                                    @96-100 Apply(
+                                        "",
+                                        "Hash",
+                                        [],
+                                    ),
+                                ],
+                            ),
+                            [
+                                Newline,
+                            ],
+                        ),
+                    ),
+                },
+            ),
+            [
+                Newline,
+                Newline,
+            ],
+        ),
+    ],
+    @103-104 SpaceBefore(
+        Num(
+            "0",
+        ),
+        [
+            Newline,
+            Newline,
+        ],
+    ),
+)

compiler/parse/tests/snapshots/pass/opaque_has_abilities.expr.roc

@@ -0,0 +1,8 @@
+A := U8 has [Eq, Hash]
+
+A := a | a has Other has [Eq, Hash]
+
+A := a | a has Other
+     has [Eq, Hash]
+
+0

compiler/parse/tests/snapshots/pass/opaque_simple.module.result-ast

@@ -12,6 +12,7 @@
                         "U8",
                         [],
                     ),
+                    derived: None,
                 },
             ),
             [],

compiler/parse/tests/snapshots/pass/opaque_with_type_arguments.module.result-ast

@@ -41,6 +41,7 @@
                         ],
                         ext: None,
                     },
+                    derived: None,
                 },
             ),
             [],

compiler/parse/tests/test_parse.rs

@@ -211,6 +211,7 @@ mod test_parse {
         pass/one_minus_two.expr,
         pass/one_plus_two.expr,
         pass/one_spaced_def.expr,
+        pass/opaque_has_abilities.expr,
         pass/opaque_simple.module,
         pass/opaque_with_type_arguments.module,
         pass/opaque_reference_expr.expr,