Use named functions for record constructors code generation

Author: abs0luty

CHANGELOG.md

@@ -51,6 +51,24 @@
   containing scientific notation or trailing zeros (i.e. `100` and `1e2`).
   ([ptdewey](https://github.com/ptdewey))
 
+- Code generation for record constructor functions with arguments has been
+  changed. They are now generated as named functions instead of anonymous
+  functions, which allows them to compare equal when referenced. For example:
+
+  ```gleam
+  pub type Foo {
+    Wibble
+    Wobble(String)
+  }
+
+  pub fn main() {
+    echo Wibble == Wibble  // True
+    echo Wobble == Wobble  // False (previously) -> True
+  }
+  ```
+
+  ([Adi Salimgereyev](https://github.com/abs0luty))
+
 ### Build tool
 
 - The help text displayed by `gleam dev --help`, `gleam test --help`, and

compiler-core/src/erlang.rs

@@ -335,8 +335,20 @@ fn register_imports_and_exports(
             typed_parameters,
             opaque,
             external_erlang,
+            publicity: _,
             ..
         }) => {
+            // Export constructor functions for constructors with arguments
+            // We need to export even for private types since they're used within the module
+            for constructor in constructors {
+                let arity = constructor.arguments.len();
+                if arity > 0 {
+                    let constructor_name = constructor_function_name(name, &constructor.name);
+
+                    exports.push(atom_string(constructor_name).append("/").append(arity));
+                }
+            }
+
             // Erlang doesn't allow phantom type variables in type definitions but gleam does
             // so we check the type declaratinon against its constroctors and generate a phantom
             // value that uses the unused type variables.
@@ -460,8 +472,11 @@ fn module_statement<'a>(
             module_function(function, module, is_internal_module, line_numbers, src_path)
         }
 
+        Definition::CustomType(CustomType {
+            name, constructors, ..
+        }) => module_constructors(name, constructors, module, line_numbers),
+
         Definition::TypeAlias(TypeAlias { .. })
-        | Definition::CustomType(CustomType { .. })
         | Definition::Import(Import { .. })
         | Definition::ModuleConstant(ModuleConstant { .. }) => None,
     }
@@ -562,6 +577,45 @@ fn module_function<'a>(
     ))
 }
 
+fn module_constructors<'a>(
+    type_name: &'a EcoString,
+    constructors: &'a [RecordConstructor<Arc<Type>>],
+    module: &'a str,
+    line_numbers: &'a LineNumbers,
+) -> Option<(Document<'a>, Env<'a>)> {
+    let constructor_functions: Vec<_> = constructors
+        .iter()
+        .filter_map(|constructor| {
+            let arity = constructor.arguments.len();
+            if arity == 0 {
+                return None;
+            }
+
+            let constructor_name = constructor_function_name(type_name, &constructor.name);
+            let record_name = to_snake_case(&constructor.name);
+            let args = incrementing_arguments_list(arity);
+
+            Some(docvec![
+                atom_string(constructor_name),
+                "(",
+                args.clone(),
+                ") -> {",
+                atom_string(record_name),
+                ", ",
+                args,
+                "}.",
+            ])
+        })
+        .collect();
+
+    if constructor_functions.is_empty() {
+        return None;
+    }
+
+    let env = Env::new(module, "", line_numbers);
+    Some((join(constructor_functions, lines(2)), env))
+}
+
 fn file_attribute<'a>(
     path: EcoString,
     function: &'a TypedFunction,
@@ -1439,18 +1493,28 @@ fn list<'a>(elements: Document<'a>, tail: Option<Document<'a>>) -> Document<'a>
 fn var<'a>(name: &'a str, constructor: &'a ValueConstructor, env: &mut Env<'a>) -> Document<'a> {
     match &constructor.variant {
         ValueConstructorVariant::Record {
-            name: record_name, ..
+            name: record_name,
+            module,
+            ..
         } => match constructor.type_.deref() {
-            Type::Fn { arguments, .. } => {
-                let chars = incrementing_arguments_list(arguments.len());
-                "fun("
-                    .to_doc()
-                    .append(chars.clone())
-                    .append(") -> {")
-                    .append(atom_string(to_snake_case(record_name)))
-                    .append(", ")
-                    .append(chars)
-                    .append("} end")
+            Type::Fn {
+                arguments, return_, ..
+            } => {
+                // Extract the type name from the return type
+                let type_name = return_
+                    .named_type_name()
+                    .map(|(_, name)| name)
+                    .unwrap_or_else(|| record_name.clone());
+                let constructor_name = constructor_function_name(&type_name, record_name);
+                let module_prefix = if module == env.module {
+                    "fun ".to_doc()
+                } else {
+                    "fun ".to_doc().append(module_name_atom(module)).append(":")
+                };
+                module_prefix
+                    .append(atom_string(constructor_name))
+                    .append("/")
+                    .append(arguments.len())
             }
             _ => atom_string(to_snake_case(record_name)),
         },
@@ -2868,6 +2932,16 @@ fn variable_name(name: &str) -> EcoString {
     first_uppercased.chain(chars).collect::<EcoString>()
 }
 
+fn constructor_function_name(type_name: &EcoString, constructor_name: &EcoString) -> EcoString {
+    // Use type$constructor naming to avoid collisions with regular functions
+    // e.g., SizedChunk.Last -> sized_chunk$last
+    eco_format!(
+        "{}${}",
+        to_snake_case(type_name),
+        to_snake_case(constructor_name)
+    )
+}
+
 /// When rendering a type variable to an erlang type spec we need all type variables with the
 /// same id to end up with the same name in the generated erlang.
 /// This function converts a usize into base 26 A-Z for this purpose.

compiler-core/src/erlang/snapshots/gleam_core__erlang__tests__field_access_function_call.snap

@@ -18,11 +18,13 @@ pub fn main() {
 -module(my@mod).
 -compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
 -define(FILEPATH, "project/test/my/mod.gleam").
--export([main/0]).
+-export(['fn_box$fn_box'/1, main/0]).
 -export_type([fn_box/0]).
 
 -type fn_box() :: {fn_box, fun((integer()) -> integer())}.
 
+'fn_box$fn_box'(Field@0) -> {fn_box, Field@0}.
+
 -file("project/test/my/mod.gleam", 6).
 -spec main() -> integer().
 main() ->

compiler-core/src/erlang/snapshots/gleam_core__erlang__tests__function_argument_shadowing.snap

@@ -16,12 +16,14 @@ pub type Box {
 -module(my@mod).
 -compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
 -define(FILEPATH, "project/test/my/mod.gleam").
--export([main/1]).
+-export(['box$box'/1, main/1]).
 -export_type([box/0]).
 
 -type box() :: {box, integer()}.
 
+'box$box'(Field@0) -> {box, Field@0}.
+
 -file("project/test/my/mod.gleam", 1).
 -spec main(any()) -> fun((integer()) -> box()).
 main(A) ->
-    fun(Field@0) -> {box, Field@0} end.
+    fun 'box$box'/1.

compiler-core/src/erlang/snapshots/gleam_core__erlang__tests__integration_test11.snap

@@ -10,11 +10,13 @@ pub fn x() { Point(x: 4, y: 6) Point(y: 1, x: 9) }
 -module(my@mod).
 -compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
 -define(FILEPATH, "project/test/my/mod.gleam").
--export([x/0]).
+-export(['point$point'/2, x/0]).
 -export_type([point/0]).
 
 -type point() :: {point, integer(), integer()}.
 
+'point$point'(Field@0, Field@1) -> {point, Field@0, Field@1}.
+
 -file("project/test/my/mod.gleam", 2).
 -spec x() -> point().
 x() ->

compiler-core/src/erlang/snapshots/gleam_core__erlang__tests__integration_test12.snap

@@ -10,11 +10,13 @@ pub fn x(y) { let Point(a, b) = y a }
 -module(my@mod).
 -compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
 -define(FILEPATH, "project/test/my/mod.gleam").
--export([x/1]).
+-export(['point$point'/2, x/1]).
 -export_type([point/0]).
 
 -type point() :: {point, integer(), integer()}.
 
+'point$point'(Field@0, Field@1) -> {point, Field@0, Field@1}.
+
 -file("project/test/my/mod.gleam", 2).
 -spec x(point()) -> integer().
 x(Y) ->

compiler-core/src/erlang/snapshots/gleam_core__erlang__tests__integration_test13.snap

@@ -11,11 +11,15 @@ pub type State{ Start(Int) End(Int) }
 -module(my@mod).
 -compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
 -define(FILEPATH, "project/test/my/mod.gleam").
--export([build/1, main/0]).
+-export(['state$start'/1, 'state$end'/1, build/1, main/0]).
 -export_type([state/0]).
 
 -type state() :: {start, integer()} | {'end', integer()}.
 
+'state$start'(Field@0) -> {start, Field@0}.
+
+'state$end'(Field@0) -> {'end', Field@0}.
+
 -file("project/test/my/mod.gleam", 2).
 -spec build(fun((integer()) -> I)) -> I.
 build(Constructor) ->
@@ -24,4 +28,4 @@ build(Constructor) ->
 -file("project/test/my/mod.gleam", 3).
 -spec main() -> state().
 main() ->
-    build(fun(Field@0) -> {'end', Field@0} end).
+    build(fun 'state$end'/1).

compiler-core/src/erlang/snapshots/gleam_core__erlang__tests__integration_test17.snap

@@ -12,11 +12,13 @@ pub fn create_user(user_id) { User(age: 22, id: user_id, name: "") }
 -module(my@mod).
 -compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
 -define(FILEPATH, "project/test/my/mod.gleam").
--export([create_user/1]).
+-export(['user$user'/3, create_user/1]).
 -export_type([user/0]).
 
 -type user() :: {user, integer(), binary(), integer()}.
 
+'user$user'(Field@0, Field@1, Field@2) -> {user, Field@0, Field@1, Field@2}.
+
 -file("project/test/my/mod.gleam", 3).
 -spec create_user(integer()) -> user().
 create_user(User_id) ->

compiler-core/src/erlang/snapshots/gleam_core__erlang__tests__integration_test19.snap

@@ -10,11 +10,13 @@ pub fn x() { X(x: 1, y: 2.) X(y: 3., x: 4) }
 -module(my@mod).
 -compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
 -define(FILEPATH, "project/test/my/mod.gleam").
--export([x/0]).
+-export(['x$x'/2, x/0]).
 -export_type([x/0]).
 
 -type x() :: {x, integer(), float()}.
 
+'x$x'(Field@0, Field@1) -> {x, Field@0, Field@1}.
+
 -file("project/test/my/mod.gleam", 2).
 -spec x() -> x().
 x() ->

compiler-core/src/erlang/snapshots/gleam_core__erlang__tests__integration_test1_1.snap

@@ -10,11 +10,13 @@ pub fn pound(x) { Pound(x) }
 -module(my@mod).
 -compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
 -define(FILEPATH, "project/test/my/mod.gleam").
--export([pound/1]).
+-export(['money$pound'/1, pound/1]).
 -export_type([money/0]).
 
 -type money() :: {pound, integer()}.
 
+'money$pound'(Field@0) -> {pound, Field@0}.
+
 -file("project/test/my/mod.gleam", 2).
 -spec pound(integer()) -> money().
 pound(X) ->