forked from
gleam.run/gleam
⭐️ A friendly language for building type-safe, scalable systems!
Add relevant suggestion when a type annotation uses angle brackets
authored by
Aaron Christiansen
and committed by
Louis Pilfold
(Sep 8, 2025, 1:04 PM +0100)
b23e00f9
4f5991c6
+94
-6
+7
-2
compiler-core/src/parse.rs
+7
-2
compiler-core/src/parse.rs
···
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Ok((start, upname, arguments2, par_e, end))
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} else if let Some((less_start, less_end)) = self.maybe_one(&Token::Less) {
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Err(ParseError {
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error: ParseErrorType::TypeAngleGenerics,
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+
error: ParseErrorType::TypeDefinitionAngleGenerics,
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location: SrcSpan {
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start: less_start,
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end: less_end,
···
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arguments,
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})))
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} else if let Some((less_start, less_end)) = self.maybe_one(&Token::Less) {
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let arguments = self.parse_types()?;
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Err(ParseError {
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error: ParseErrorType::TypeAngleGenerics,
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error: ParseErrorType::TypeUsageAngleGenerics {
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name,
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module: module.map(|(module_name, _)| module_name),
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arguments,
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},
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location: SrcSpan {
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start: less_start,
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end: less_end,
+42
-2
compiler-core/src/parse/error.rs
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-2
compiler-core/src/parse/error.rs
···
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// When the use tries to define a constant inside a function
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ConstantInsideFunction,
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FunctionDefinitionAngleGenerics, // fn something<T>() { ... }
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-
TypeAngleGenerics, // let a: List<String> = []
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+
// let a: List<String> = []
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TypeUsageAngleGenerics {
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module: Option<EcoString>,
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name: EcoString,
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arguments: Vec<TypeAst>,
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},
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// type Something<T> {
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TypeDefinitionAngleGenerics,
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}
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pub(crate) struct ParseErrorDetails {
···
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extra_labels: vec![],
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},
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-
ParseErrorType::TypeAngleGenerics => ParseErrorDetails {
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ParseErrorType::TypeUsageAngleGenerics {
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module,
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name,
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arguments,
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} => {
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let type_arguments = arguments
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.iter()
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.map(|argument| {
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let mut argument_string = EcoString::new();
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argument.print(&mut argument_string);
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argument_string
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})
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.join(", ");
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let replacement_type = match module {
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Some(module) => format!("{module}.{name}({type_arguments})"),
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None => format!("{name}({type_arguments})"),
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};
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+
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ParseErrorDetails {
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text: format!(
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"\
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Type parameters use lowercase names and are surrounded by parentheses.
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+
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{replacement_type}
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+
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See: https://tour.gleam.run/data-types/generic-custom-types/"
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),
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hint: None,
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label_text: "I was expecting `(` here.".into(),
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extra_labels: vec![],
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}
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}
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+
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+
ParseErrorType::TypeDefinitionAngleGenerics => ParseErrorDetails {
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text: "\
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Type parameters use lowercase names and are surrounded by parentheses.
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+19
compiler-core/src/parse/snapshots/gleam_core__parse__tests__type_angle_generics_usage_with_module_error.snap
+19
compiler-core/src/parse/snapshots/gleam_core__parse__tests__type_angle_generics_usage_with_module_error.snap
···
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+
---
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source: compiler-core/src/parse/tests.rs
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expression: "let set: set.Set<Int> = set.new()"
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---
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----- SOURCE CODE
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let set: set.Set<Int> = set.new()
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+
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----- ERROR
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error: Syntax error
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┌─ /src/parse/error.gleam:1:17
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│
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1 │ let set: set.Set<Int> = set.new()
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│ ^ I was expecting `(` here.
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+
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Type parameters use lowercase names and are surrounded by parentheses.
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+
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set.Set(Int)
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+
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+
See: https://tour.gleam.run/data-types/generic-custom-types/
+19
compiler-core/src/parse/snapshots/gleam_core__parse__tests__type_angle_generics_usage_without_module_error.snap
+19
compiler-core/src/parse/snapshots/gleam_core__parse__tests__type_angle_generics_usage_without_module_error.snap
···
1
+
---
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+
source: compiler-core/src/parse/tests.rs
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expression: "let list: List<Int, String> = []"
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+
---
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----- SOURCE CODE
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let list: List<Int, String> = []
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+
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----- ERROR
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error: Syntax error
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┌─ /src/parse/error.gleam:1:15
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│
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1 │ let list: List<Int, String> = []
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│ ^ I was expecting `(` here.
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+
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Type parameters use lowercase names and are surrounded by parentheses.
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+
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List(Int, String)
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+
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+
See: https://tour.gleam.run/data-types/generic-custom-types/
+7
-2
compiler-core/src/parse/tests.rs
+7
-2
compiler-core/src/parse/tests.rs
···
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}
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#[test]
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-
fn type_angle_generics_usage_error() {
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-
assert_error!("let list: List<Int> = []");
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+
fn type_angle_generics_usage_without_module_error() {
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+
assert_error!("let list: List<Int, String> = []");
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+
}
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+
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+
#[test]
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fn type_angle_generics_usage_with_module_error() {
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assert_error!("let set: set.Set<Int> = set.new()");
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}
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#[test]