Auto merge of #14354 - Veykril:sighelp, r=Veykril

feat: Add signature help for record and tuple struct patterns

6 files changed, 281 insertions, 19 deletions

diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index ab39542f9fa..407ba6f6584 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -411,7 +411,7 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         self.imp.resolve_record_field(field)
     }
 
-    pub fn resolve_record_pat_field(&self, field: &ast::RecordPatField) -> Option<Field> {
+    pub fn resolve_record_pat_field(&self, field: &ast::RecordPatField) -> Option<(Field, Type)> {
         self.imp.resolve_record_pat_field(field)
     }
 
@@ -1201,7 +1201,7 @@ impl<'db> SemanticsImpl<'db> {
         self.analyze(field.syntax())?.resolve_record_field(self.db, field)
     }
 
-    fn resolve_record_pat_field(&self, field: &ast::RecordPatField) -> Option<Field> {
+    fn resolve_record_pat_field(&self, field: &ast::RecordPatField) -> Option<(Field, Type)> {
         self.analyze(field.syntax())?.resolve_record_pat_field(self.db, field)
     }
 
diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
index 133fa810d66..c24d196e1b6 100644
--- a/crates/hir/src/source_analyzer.rs
+++ b/crates/hir/src/source_analyzer.rs
@@ -441,14 +441,17 @@ impl SourceAnalyzer {
         &self,
         db: &dyn HirDatabase,
         field: &ast::RecordPatField,
-    ) -> Option<Field> {
+    ) -> Option<(Field, Type)> {
         let field_name = field.field_name()?.as_name();
         let record_pat = ast::RecordPat::cast(field.syntax().parent().and_then(|p| p.parent())?)?;
         let pat_id = self.pat_id(&record_pat.into())?;
         let variant = self.infer.as_ref()?.variant_resolution_for_pat(pat_id)?;
         let variant_data = variant.variant_data(db.upcast());
         let field = FieldId { parent: variant, local_id: variant_data.field(&field_name)? };
-        Some(field.into())
+        let (_, subst) = self.infer.as_ref()?.type_of_pat.get(pat_id)?.as_adt()?;
+        let field_ty =
+            db.field_types(variant).get(field.local_id)?.clone().substitute(Interner, subst);
+        Some((field.into(), Type::new_with_resolver(db, &self.resolver, field_ty)))
     }
 
     pub(crate) fn resolve_macro_call(
diff --git a/crates/ide-db/src/defs.rs b/crates/ide-db/src/defs.rs
index 1322f5228e8..4071c490b7f 100644
--- a/crates/ide-db/src/defs.rs
+++ b/crates/ide-db/src/defs.rs
@@ -327,7 +327,7 @@ impl NameClass {
             let pat_parent = ident_pat.syntax().parent();
             if let Some(record_pat_field) = pat_parent.and_then(ast::RecordPatField::cast) {
                 if record_pat_field.name_ref().is_none() {
-                    if let Some(field) = sema.resolve_record_pat_field(&record_pat_field) {
+                    if let Some((field, _)) = sema.resolve_record_pat_field(&record_pat_field) {
                         return Some(NameClass::PatFieldShorthand {
                             local_def: local,
                             field_ref: field,
@@ -483,6 +483,13 @@ impl NameRefClass {
                 },
                 ast::RecordPatField(record_pat_field) => {
                     sema.resolve_record_pat_field(&record_pat_field)
+                        .map(|(field, ..)|field)
+                        .map(Definition::Field)
+                        .map(NameRefClass::Definition)
+                },
+                ast::RecordExprField(record_expr_field) => {
+                    sema.resolve_record_field(&record_expr_field)
+                        .map(|(field, ..)|field)
                         .map(Definition::Field)
                         .map(NameRefClass::Definition)
                 },
diff --git a/crates/ide/src/goto_type_definition.rs b/crates/ide/src/goto_type_definition.rs
index 55cdb3200ea..6d2d0bd6351 100644
--- a/crates/ide/src/goto_type_definition.rs
+++ b/crates/ide/src/goto_type_definition.rs
@@ -55,7 +55,7 @@ pub(crate) fn goto_type_definition(
                                 ty
                             } else {
                                 let record_field = ast::RecordPatField::for_field_name_ref(&it)?;
-                                sema.resolve_record_pat_field(&record_field)?.ty(db)
+                                sema.resolve_record_pat_field(&record_field)?.1
                             }
                         },
                         _ => return None,
diff --git a/crates/ide/src/signature_help.rs b/crates/ide/src/signature_help.rs
index 2c08c457b33..4b2c139f6f4 100644
--- a/crates/ide/src/signature_help.rs
+++ b/crates/ide/src/signature_help.rs
@@ -16,7 +16,7 @@ use stdx::format_to;
 use syntax::{
     algo,
     ast::{self, HasArgList},
-    match_ast, AstNode, Direction, SyntaxToken, TextRange, TextSize,
+    match_ast, AstNode, Direction, SyntaxElementChildren, SyntaxToken, TextRange, TextSize,
 };
 
 use crate::RootDatabase;
@@ -102,6 +102,20 @@ pub(crate) fn signature_help(db: &RootDatabase, position: FilePosition) -> Optio
                     }
                     return signature_help_for_record_lit(&sema, record, token);
                 },
+                ast::RecordPat(record) => {
+                    let cursor_outside = record.record_pat_field_list().and_then(|list| list.r_curly_token()).as_ref() == Some(&token);
+                    if cursor_outside {
+                        continue;
+                    }
+                    return signature_help_for_record_pat(&sema, record, token);
+                },
+                ast::TupleStructPat(tuple_pat) => {
+                    let cursor_outside = tuple_pat.r_paren_token().as_ref() == Some(&token);
+                    if cursor_outside {
+                        continue;
+                    }
+                    return signature_help_for_tuple_struct_pat(&sema, tuple_pat, token);
+                },
                 _ => (),
             }
         }
@@ -346,11 +360,112 @@ fn signature_help_for_record_lit(
     record: ast::RecordExpr,
     token: SyntaxToken,
 ) -> Option<SignatureHelp> {
-    let active_parameter = record
-        .record_expr_field_list()?
+    signature_help_for_record_(
+        sema,
+        record.record_expr_field_list()?.syntax().children_with_tokens(),
+        &record.path()?,
+        record
+            .record_expr_field_list()?
+            .fields()
+            .filter_map(|field| sema.resolve_record_field(&field))
+            .map(|(field, _, ty)| (field, ty)),
+        token,
+    )
+}
+
+fn signature_help_for_record_pat(
+    sema: &Semantics<'_, RootDatabase>,
+    record: ast::RecordPat,
+    token: SyntaxToken,
+) -> Option<SignatureHelp> {
+    signature_help_for_record_(
+        sema,
+        record.record_pat_field_list()?.syntax().children_with_tokens(),
+        &record.path()?,
+        record
+            .record_pat_field_list()?
+            .fields()
+            .filter_map(|field| sema.resolve_record_pat_field(&field)),
+        token,
+    )
+}
+
+fn signature_help_for_tuple_struct_pat(
+    sema: &Semantics<'_, RootDatabase>,
+    pat: ast::TupleStructPat,
+    token: SyntaxToken,
+) -> Option<SignatureHelp> {
+    let rest_pat = pat.fields().find(|it| matches!(it, ast::Pat::RestPat(_)));
+    let is_left_of_rest_pat =
+        rest_pat.map_or(true, |it| token.text_range().start() < it.syntax().text_range().end());
+
+    let mut res = SignatureHelp {
+        doc: None,
+        signature: String::new(),
+        parameters: vec![],
+        active_parameter: None,
+    };
+
+    let db = sema.db;
+    let path_res = sema.resolve_path(&pat.path()?)?;
+    let fields: Vec<_> = if let PathResolution::Def(ModuleDef::Variant(variant)) = path_res {
+        let en = variant.parent_enum(db);
+
+        res.doc = en.docs(db).map(|it| it.into());
+        format_to!(res.signature, "enum {}::{} (", en.name(db), variant.name(db));
+        variant.fields(db)
+    } else {
+        let adt = match path_res {
+            PathResolution::SelfType(imp) => imp.self_ty(db).as_adt()?,
+            PathResolution::Def(ModuleDef::Adt(adt)) => adt,
+            _ => return None,
+        };
+
+        match adt {
+            hir::Adt::Struct(it) => {
+                res.doc = it.docs(db).map(|it| it.into());
+                format_to!(res.signature, "struct {} (", it.name(db));
+                it.fields(db)
+            }
+            _ => return None,
+        }
+    };
+    let commas = pat
         .syntax()
         .children_with_tokens()
         .filter_map(syntax::NodeOrToken::into_token)
+        .filter(|t| t.kind() == syntax::T![,]);
+    res.active_parameter = Some(if is_left_of_rest_pat {
+        commas.take_while(|t| t.text_range().start() <= token.text_range().start()).count()
+    } else {
+        let n_commas = commas
+            .collect::<Vec<_>>()
+            .into_iter()
+            .rev()
+            .take_while(|t| t.text_range().start() > token.text_range().start())
+            .count();
+        fields.len().saturating_sub(1).saturating_sub(n_commas)
+    });
+
+    let mut buf = String::new();
+    for ty in fields.into_iter().map(|it| it.ty(db)) {
+        format_to!(buf, "{}", ty.display_truncated(db, Some(20)));
+        res.push_call_param(&buf);
+        buf.clear();
+    }
+    res.signature.push_str(")");
+    Some(res)
+}
+
+fn signature_help_for_record_(
+    sema: &Semantics<'_, RootDatabase>,
+    field_list_children: SyntaxElementChildren,
+    path: &ast::Path,
+    fields2: impl Iterator<Item = (hir::Field, hir::Type)>,
+    token: SyntaxToken,
+) -> Option<SignatureHelp> {
+    let active_parameter = field_list_children
+        .filter_map(syntax::NodeOrToken::into_token)
         .filter(|t| t.kind() == syntax::T![,])
         .take_while(|t| t.text_range().start() <= token.text_range().start())
         .count();
@@ -365,7 +480,7 @@ fn signature_help_for_record_lit(
     let fields;
 
     let db = sema.db;
-    let path_res = sema.resolve_path(&record.path()?)?;
+    let path_res = sema.resolve_path(path)?;
     if let PathResolution::Def(ModuleDef::Variant(variant)) = path_res {
         fields = variant.fields(db);
         let en = variant.parent_enum(db);
@@ -397,8 +512,7 @@ fn signature_help_for_record_lit(
     let mut fields =
         fields.into_iter().map(|field| (field.name(db), Some(field))).collect::<FxIndexMap<_, _>>();
     let mut buf = String::new();
-    for field in record.record_expr_field_list()?.fields() {
-        let Some((field, _, ty)) = sema.resolve_record_field(&field) else { continue };
+    for (field, ty) in fields2 {
         let name = field.name(db);
         format_to!(buf, "{name}: {}", ty.display_truncated(db, Some(20)));
         res.push_record_field(&buf);
@@ -439,6 +553,7 @@ mod tests {
         (database, FilePosition { file_id, offset })
     }
 
+    #[track_caller]
     fn check(ra_fixture: &str, expect: Expect) {
         let fixture = format!(
             r#"
@@ -891,6 +1006,119 @@ fn main() {
     }
 
     #[test]
+    fn tuple_struct_pat() {
+        check(
+            r#"
+/// A cool tuple struct
+struct S(u32, i32);
+fn main() {
+    let S(0, $0);
+}
+"#,
+            expect![[r#"
+                A cool tuple struct
+                ------
+                struct S (u32, i32)
+                          ---  ^^^
+            "#]],
+        );
+    }
+
+    #[test]
+    fn tuple_struct_pat_rest() {
+        check(
+            r#"
+/// A cool tuple struct
+struct S(u32, i32, f32, u16);
+fn main() {
+    let S(0, .., $0);
+}
+"#,
+            expect![[r#"
+                A cool tuple struct
+                ------
+                struct S (u32, i32, f32, u16)
+                          ---  ---  ---  ^^^
+            "#]],
+        );
+        check(
+            r#"
+/// A cool tuple struct
+struct S(u32, i32, f32, u16, u8);
+fn main() {
+    let S(0, .., $0, 0);
+}
+"#,
+            expect![[r#"
+                A cool tuple struct
+                ------
+                struct S (u32, i32, f32, u16, u8)
+                          ---  ---  ---  ^^^  --
+            "#]],
+        );
+        check(
+            r#"
+/// A cool tuple struct
+struct S(u32, i32, f32, u16);
+fn main() {
+    let S($0, .., 1);
+}
+"#,
+            expect![[r#"
+                A cool tuple struct
+                ------
+                struct S (u32, i32, f32, u16)
+                          ^^^  ---  ---  ---
+            "#]],
+        );
+        check(
+            r#"
+/// A cool tuple struct
+struct S(u32, i32, f32, u16, u8);
+fn main() {
+    let S(1, .., 1, $0, 2);
+}
+"#,
+            expect![[r#"
+                A cool tuple struct
+                ------
+                struct S (u32, i32, f32, u16, u8)
+                          ---  ---  ---  ^^^  --
+            "#]],
+        );
+        check(
+            r#"
+/// A cool tuple struct
+struct S(u32, i32, f32, u16);
+fn main() {
+    let S(1, $0.., 1);
+}
+"#,
+            expect![[r#"
+                A cool tuple struct
+                ------
+                struct S (u32, i32, f32, u16)
+                          ---  ^^^  ---  ---
+            "#]],
+        );
+        check(
+            r#"
+/// A cool tuple struct
+struct S(u32, i32, f32, u16);
+fn main() {
+    let S(1, ..$0, 1);
+}
+"#,
+            expect![[r#"
+                A cool tuple struct
+                ------
+                struct S (u32, i32, f32, u16)
+                          ---  ^^^  ---  ---
+            "#]],
+        );
+    }
+
+    #[test]
     fn generic_struct() {
         check(
             r#"
@@ -1551,6 +1779,29 @@ impl S {
     }
 
     #[test]
+    fn record_pat() {
+        check(
+            r#"
+struct Strukt<T, U = ()> {
+    t: T,
+    u: U,
+    unit: (),
+}
+fn f() {
+    let Strukt {
+        u: 0,
+        $0
+    }
+}
+"#,
+            expect![[r#"
+                struct Strukt { u: i32, t: T, unit: () }
+                                ------  ^^^^  --------
+            "#]],
+        );
+    }
+
+    #[test]
     fn test_enum_in_nested_method_in_lambda() {
         check(
             r#"
diff --git a/crates/parser/src/grammar/patterns.rs b/crates/parser/src/grammar/patterns.rs
index abcefffa23f..5f4977886f6 100644
--- a/crates/parser/src/grammar/patterns.rs
+++ b/crates/parser/src/grammar/patterns.rs
@@ -431,14 +431,15 @@ fn slice_pat(p: &mut Parser<'_>) -> CompletedMarker {
 
 fn pat_list(p: &mut Parser<'_>, ket: SyntaxKind) {
     while !p.at(EOF) && !p.at(ket) {
-        if !p.at_ts(PAT_TOP_FIRST) {
-            p.error("expected a pattern");
-            break;
-        }
-
         pattern_top(p);
-        if !p.at(ket) {
-            p.expect(T![,]);
+        if !p.at(T![,]) {
+            if p.at_ts(PAT_TOP_FIRST) {
+                p.error(format!("expected {:?}, got {:?}", T![,], p.current()));
+            } else {
+                break;
+            }
+        } else {
+            p.bump(T![,]);
         }
     }
 }