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feat: enhance signature help to display generic parameters for callables and default values for generic args #19596

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merged 1 commit into from
Apr 16, 2025
+154 −13
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feat: enhance signature help to display generic parameters for callables and default values for generic args #19596

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167 changes: 154 additions & 13 deletions crates/ide/src/signature_help.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,13 +5,15 @@ use std::collections::BTreeSet;

use either::Either;
use hir::{
AssocItem, DisplayTarget, GenericParam, HirDisplay, ModuleDef, PathResolution, Semantics, Trait,
AssocItem, DisplayTarget, GenericDef, GenericParam, HirDisplay, ModuleDef, PathResolution,
Semantics, Trait,
};
use ide_db::{
FilePosition, FxIndexMap,
active_parameter::{callable_for_arg_list, generic_def_for_node},
documentation::{Documentation, HasDocs},
};
use itertools::Itertools;
use span::Edition;
use stdx::format_to;
use syntax::{
Expand Down Expand Up @@ -175,6 +177,20 @@ fn signature_help_for_call(
hir::CallableKind::Function(func) => {
res.doc = func.docs(db);
format_to!(res.signature, "fn {}", func.name(db).display(db, edition));

let generic_params = GenericDef::Function(func)
.params(db)
.iter()
.filter(|param| match param {
GenericParam::TypeParam(type_param) => !type_param.is_implicit(db),
GenericParam::ConstParam(_) | GenericParam::LifetimeParam(_) => true,
})
.map(|param| param.display(db, display_target))
.join(", ");
if !generic_params.is_empty() {
format_to!(res.signature, "<{}>", generic_params);
}

fn_params = Some(match callable.receiver_param(db) {
Some(_self) => func.params_without_self(db),
None => func.assoc_fn_params(db),
Expand All @@ -183,15 +199,34 @@ fn signature_help_for_call(
hir::CallableKind::TupleStruct(strukt) => {
res.doc = strukt.docs(db);
format_to!(res.signature, "struct {}", strukt.name(db).display(db, edition));

let generic_params = GenericDef::Adt(strukt.into())
.params(db)
.iter()
.map(|param| param.display(db, display_target))
.join(", ");
if !generic_params.is_empty() {
format_to!(res.signature, "<{}>", generic_params);
}
}
hir::CallableKind::TupleEnumVariant(variant) => {
res.doc = variant.docs(db);
format_to!(
res.signature,
"enum {}::{}",
"enum {}",
variant.parent_enum(db).name(db).display(db, edition),
variant.name(db).display(db, edition)
);

let generic_params = GenericDef::Adt(variant.parent_enum(db).into())
.params(db)
.iter()
.map(|param| param.display(db, display_target))
.join(", ");
if !generic_params.is_empty() {
format_to!(res.signature, "<{}>", generic_params);
}

format_to!(res.signature, "::{}", variant.name(db).display(db, edition))
}
hir::CallableKind::Closure(closure) => {
let fn_trait = closure.fn_trait(db);
Expand Down Expand Up @@ -339,6 +374,20 @@ fn signature_help_for_generics(

buf.clear();
format_to!(buf, "{}", param.display(db, display_target));
match param {
GenericParam::TypeParam(param) => {
if let Some(ty) = param.default(db) {
format_to!(buf, " = {}", ty.display(db, display_target));
}
}
GenericParam::ConstParam(param) => {
if let Some(expr) = param.default(db, display_target).and_then(|konst| konst.expr())
{
format_to!(buf, " = {}", expr);
}
}
_ => {}
}
res.push_generic_param(&buf);
}
if let hir::GenericDef::Trait(tr) = generics_def {
Expand Down Expand Up @@ -815,8 +864,8 @@ fn foo<T, U: Copy + Display>(x: T, y: U) -> u32
fn bar() { foo($03, ); }
"#,
expect![[r#"
fn foo(x: i32, y: U) -> u32
^^^^^^ ----
fn foo<T, U>(x: i32, y: U) -> u32
^^^^^^ ----
"#]],
);
}
Expand All @@ -829,7 +878,7 @@ fn foo<T>() -> T where T: Copy + Display {}
fn bar() { foo($0); }
"#,
expect![[r#"
fn foo() -> T
fn foo<T>() -> T
"#]],
);
}
Expand Down Expand Up @@ -1279,8 +1328,8 @@ fn main() {
}
"#,
expect![[r#"
struct S({unknown})
^^^^^^^^^
struct S<T>({unknown})
^^^^^^^^^
"#]],
);
}
Expand Down Expand Up @@ -1375,7 +1424,7 @@ id! {
fn test() { S.foo($0); }
"#,
expect![[r#"
fn foo(&'a mut self)
fn foo<'a>(&'a mut self)
"#]],
);
}
Expand Down Expand Up @@ -1724,8 +1773,8 @@ fn sup() {
}
"#,
expect![[r#"
fn test(&mut self, val: V)
^^^^^^
fn test<V>(&mut self, val: V)
^^^^^^
"#]],
);
}
Expand Down Expand Up @@ -1901,8 +1950,8 @@ fn f() {
}
"#,
expect![[r#"
fn foo(x: Wrap<impl Trait<U>>)
^^^^^^^^^^^^^^^^^^^^^^
fn foo<U>(x: Wrap<impl Trait<U>>)
^^^^^^^^^^^^^^^^^^^^^^
"#]],
);
}
Expand Down Expand Up @@ -2394,4 +2443,96 @@ fn main() {
"#]],
);
}

#[test]
fn test_tuple_generic_param() {
check(
r#"
struct S<T>(T);
fn main() {
let s: S<$0
}
"#,
expect![[r#"
struct S<T>
^
"#]],
);
}

#[test]
fn test_enum_generic_param() {
check(
r#"
enum Option<T> {
Some(T),
None,
}
fn main() {
let opt: Option<$0
}
"#,
expect![[r#"
enum Option<T>
^
"#]],
);
}

#[test]
fn test_enum_variant_generic_param() {
check(
r#"
enum Option<T> {
Some(T),
None,
}
fn main() {
let opt = Option::Some($0);
}
"#,
expect![[r#"
enum Option<T>::Some({unknown})
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Would be nice if this said enum Option<T>::Some(T), we should open a follow up issue for that

^^^^^^^^^
"#]],
);
}

#[test]
fn test_generic_arg_with_default() {
check(
r#"
struct S<T = u8> {
field: T,
}
fn main() {
let s: S<$0
}
"#,
expect![[r#"
struct S<T = u8>
^^^^^^
"#]],
);

check(
r#"
struct S<const C: u8 = 5> {
field: C,
}
fn main() {
let s: S<$0
}
"#,
expect![[r#"
struct S<const C: u8 = 5>
^^^^^^^^^^^^^^^
"#]],
);
}
}