Auto merge of rust-lang#18038 - roife:fix-issue-18034, r=Veykril

feat: generate names for tuple-struct in add-missing-match-arms

fix rust-lang#18034.

This PR includes the following enhancement:

- Introduced a `NameGenerator` in `suggest_name`, which implements an automatic renaming algorithm to avoid name conflicts. Here are a few examples:

```rust
let mut generator = NameGenerator::new();
assert_eq!(generator.suggest_name("a"), "a");
assert_eq!(generator.suggest_name("a"), "a1");
assert_eq!(generator.suggest_name("a"), "a2");

assert_eq!(generator.suggest_name("b"), "b");
assert_eq!(generator.suggest_name("b"), "b1");
assert_eq!(generator.suggest_name("b2"), "b2");
assert_eq!(generator.suggest_name("b"), "b3");
assert_eq!(generator.suggest_name("b"), "b4");
assert_eq!(generator.suggest_name("b3"), "b5");
```

- Updated existing testcases in ide-assists for the new `NameGenerator` (only modified generated names).
- Generate names for tuple structs instead of using wildcard patterns in `add-missing-match-arms`.

src/tools/rust-analyzer/crates/ide-assists/src/handlers/add_missing_match_arms.rs

@@ -1,12 +1,13 @@
 use std::iter::{self, Peekable};
 
 use either::Either;
-use hir::{sym, Adt, Crate, HasAttrs, HasSource, ImportPathConfig, ModuleDef, Semantics};
+use hir::{sym, Adt, Crate, HasAttrs, ImportPathConfig, ModuleDef, Semantics};
+use ide_db::syntax_helpers::suggest_name;
 use ide_db::RootDatabase;
 use ide_db::{famous_defs::FamousDefs, helpers::mod_path_to_ast};
 use itertools::Itertools;
 use syntax::ast::edit_in_place::Removable;
-use syntax::ast::{self, make, AstNode, HasName, MatchArmList, MatchExpr, Pat};
+use syntax::ast::{self, make, AstNode, MatchArmList, MatchExpr, Pat};
 
 use crate::{utils, AssistContext, AssistId, AssistKind, Assists};
 
@@ -90,7 +91,7 @@ pub(crate) fn add_missing_match_arms(acc: &mut Assists, ctx: &AssistContext<'_>)
             .into_iter()
             .filter_map(|variant| {
                 Some((
-                    build_pat(ctx.db(), module, variant, cfg)?,
+                    build_pat(ctx, module, variant, cfg)?,
                     variant.should_be_hidden(ctx.db(), module.krate()),
                 ))
             })
@@ -141,9 +142,8 @@ pub(crate) fn add_missing_match_arms(acc: &mut Assists, ctx: &AssistContext<'_>)
                 let is_hidden = variants
                     .iter()
                     .any(|variant| variant.should_be_hidden(ctx.db(), module.krate()));
-                let patterns = variants
-                    .into_iter()
-                    .filter_map(|variant| build_pat(ctx.db(), module, variant, cfg));
+                let patterns =
+                    variants.into_iter().filter_map(|variant| build_pat(ctx, module, variant, cfg));
 
                 (ast::Pat::from(make::tuple_pat(patterns)), is_hidden)
             })
@@ -174,9 +174,8 @@ pub(crate) fn add_missing_match_arms(acc: &mut Assists, ctx: &AssistContext<'_>)
                 let is_hidden = variants
                     .iter()
                     .any(|variant| variant.should_be_hidden(ctx.db(), module.krate()));
-                let patterns = variants
-                    .into_iter()
-                    .filter_map(|variant| build_pat(ctx.db(), module, variant, cfg));
+                let patterns =
+                    variants.into_iter().filter_map(|variant| build_pat(ctx, module, variant, cfg));
                 (ast::Pat::from(make::slice_pat(patterns)), is_hidden)
             })
             .filter(|(variant_pat, _)| is_variant_missing(&top_lvl_pats, variant_pat));
@@ -438,33 +437,39 @@ fn resolve_array_of_enum_def(
 }
 
 fn build_pat(
-    db: &RootDatabase,
+    ctx: &AssistContext<'_>,
     module: hir::Module,
     var: ExtendedVariant,
     cfg: ImportPathConfig,
 ) -> Option<ast::Pat> {
+    let db = ctx.db();
     match var {
         ExtendedVariant::Variant(var) => {
             let edition = module.krate().edition(db);
             let path = mod_path_to_ast(&module.find_path(db, ModuleDef::from(var), cfg)?, edition);
-            // FIXME: use HIR for this; it doesn't currently expose struct vs. tuple vs. unit variants though
-            Some(match var.source(db)?.value.kind() {
-                ast::StructKind::Tuple(field_list) => {
-                    let pats =
-                        iter::repeat(make::wildcard_pat().into()).take(field_list.fields().count());
+            let fields = var.fields(db);
+            let pat = match var.kind(db) {
+                hir::StructKind::Tuple => {
+                    let mut name_generator = suggest_name::NameGenerator::new();
+                    let pats = fields.into_iter().map(|f| {
+                        let name = name_generator.for_type(&f.ty(db), db, edition);
+                        match name {
+                            Some(name) => make::ext::simple_ident_pat(make::name(&name)).into(),
+                            None => make::wildcard_pat().into(),
+                        }
+                    });
                     make::tuple_struct_pat(path, pats).into()
                 }
-                ast::StructKind::Record(field_list) => {
-                    let pats = field_list.fields().map(|f| {
-                        make::ext::simple_ident_pat(
-                            f.name().expect("Record field must have a name"),
-                        )
-                        .into()
-                    });
+                hir::StructKind::Record => {
+                    let pats = fields
+                        .into_iter()
+                        .map(|f| make::name(f.name(db).as_str()))
+                        .map(|name| make::ext::simple_ident_pat(name).into());
                     make::record_pat(path, pats).into()
                 }
-                ast::StructKind::Unit => make::path_pat(path),
-            })
+                hir::StructKind::Unit => make::path_pat(path),
+            };
+            Some(pat)
         }
         ExtendedVariant::True => Some(ast::Pat::from(make::literal_pat("true"))),
         ExtendedVariant::False => Some(ast::Pat::from(make::literal_pat("false"))),
@@ -1976,4 +1981,81 @@ fn a() {
 }"#,
         )
     }
+
+    #[test]
+    fn suggest_name_for_tuple_struct_patterns() {
+        // single tuple struct
+        check_assist(
+            add_missing_match_arms,
+            r#"
+struct S;
+
+pub enum E {
+    A
+    B(S),
+}
+
+fn f() {
+    let value = E::A;
+    match value {
+        $0
+    }
+}
+"#,
+            r#"
+struct S;
+
+pub enum E {
+    A
+    B(S),
+}
+
+fn f() {
+    let value = E::A;
+    match value {
+        $0E::A => todo!(),
+        E::B(s) => todo!(),
+    }
+}
+"#,
+        );
+
+        // multiple tuple struct patterns
+        check_assist(
+            add_missing_match_arms,
+            r#"
+struct S1;
+struct S2;
+
+pub enum E {
+    A
+    B(S1, S2),
+}
+
+fn f() {
+    let value = E::A;
+    match value {
+        $0
+    }
+}
+"#,
+            r#"
+struct S1;
+struct S2;
+
+pub enum E {
+    A
+    B(S1, S2),
+}
+
+fn f() {
+    let value = E::A;
+    match value {
+        $0E::A => todo!(),
+        E::B(s1, s2) => todo!(),
+    }
+}
+"#,
+        );
+    }
 }

src/tools/rust-analyzer/crates/ide-assists/src/handlers/generate_delegate_trait.rs

@@ -584,7 +584,7 @@ fn resolve_name_conflicts(
 
             for old_strukt_param in old_strukt_params.generic_params() {
                 // Get old name from `strukt`
-                let mut name = SmolStr::from(match &old_strukt_param {
+                let name = SmolStr::from(match &old_strukt_param {
                     ast::GenericParam::ConstParam(c) => c.name()?.to_string(),
                     ast::GenericParam::LifetimeParam(l) => {
                         l.lifetime()?.lifetime_ident_token()?.to_string()
@@ -593,8 +593,19 @@ fn resolve_name_conflicts(
                 });
 
                 // The new name cannot be conflicted with generics in trait, and the renamed names.
-                name = suggest_name::for_unique_generic_name(&name, old_impl_params);
-                name = suggest_name::for_unique_generic_name(&name, &params);
+                let param_list_to_names = |param_list: &GenericParamList| {
+                    param_list.generic_params().flat_map(|param| match param {
+                        ast::GenericParam::TypeParam(t) => t.name().map(|name| name.to_string()),
+                        p => Some(p.to_string()),
+                    })
+                };
+                let existing_names = param_list_to_names(old_impl_params)
+                    .chain(param_list_to_names(&params))
+                    .collect_vec();
+                let mut name_generator = suggest_name::NameGenerator::new_with_names(
+                    existing_names.iter().map(|s| s.as_str()),
+                );
+                let name = name_generator.suggest_name(&name);
                 match old_strukt_param {
                     ast::GenericParam::ConstParam(c) => {
                         if let Some(const_ty) = c.ty() {
@@ -1213,9 +1224,9 @@ struct S<T> {
     b : B<T>,
 }
 
-impl<T0> Trait<T0> for S<T0> {
-    fn f(&self, a: T0) -> T0 {
-        <B<T0> as Trait<T0>>::f(&self.b, a)
+impl<T1> Trait<T1> for S<T1> {
+    fn f(&self, a: T1) -> T1 {
+        <B<T1> as Trait<T1>>::f(&self.b, a)
     }
 }
 "#,
@@ -1527,12 +1538,12 @@ where
     b : B<T, T1>,
 }
 
-impl<T, T2, T10> Trait<T> for S<T2, T10>
+impl<T, T2, T3> Trait<T> for S<T2, T3>
 where
-    T10: AnotherTrait
+    T3: AnotherTrait
 {
     fn f(&self, a: T) -> T {
-        <B<T2, T10> as Trait<T>>::f(&self.b, a)
+        <B<T2, T3> as Trait<T>>::f(&self.b, a)
     }
 }"#,
         );
@@ -1589,12 +1600,12 @@ where
     b : B<T>,
 }
 
-impl<T, T0> Trait<T> for S<T0>
+impl<T, T2> Trait<T> for S<T2>
 where
-    T0: AnotherTrait
+    T2: AnotherTrait
 {
     fn f(&self, a: T) -> T {
-        <B<T0> as Trait<T>>::f(&self.b, a)
+        <B<T2> as Trait<T>>::f(&self.b, a)
     }
 }"#,
         );

src/tools/rust-analyzer/crates/ide-assists/src/handlers/introduce_named_generic.rs

@@ -1,6 +1,7 @@
 use ide_db::syntax_helpers::suggest_name;
+use itertools::Itertools;
 use syntax::{
-    ast::{self, edit_in_place::GenericParamsOwnerEdit, make, AstNode, HasGenericParams},
+    ast::{self, edit_in_place::GenericParamsOwnerEdit, make, AstNode, HasGenericParams, HasName},
     ted,
 };
 
@@ -33,8 +34,18 @@ pub(crate) fn introduce_named_generic(acc: &mut Assists, ctx: &AssistContext<'_>
             let impl_trait_type = edit.make_mut(impl_trait_type);
             let fn_ = edit.make_mut(fn_);
             let fn_generic_param_list = fn_.get_or_create_generic_param_list();
-            let type_param_name =
-                suggest_name::for_impl_trait_as_generic(&impl_trait_type, &fn_generic_param_list);
+
+            let existing_names = fn_generic_param_list
+                .generic_params()
+                .flat_map(|param| match param {
+                    ast::GenericParam::TypeParam(t) => t.name().map(|name| name.to_string()),
+                    p => Some(p.to_string()),
+                })
+                .collect_vec();
+            let type_param_name = suggest_name::NameGenerator::new_with_names(
+                existing_names.iter().map(|s| s.as_str()),
+            )
+            .for_impl_trait_as_generic(&impl_trait_type);
 
             let type_param = make::type_param(make::name(&type_param_name), Some(type_bound_list))
                 .clone_for_update();
@@ -116,7 +127,7 @@ fn foo<$0B: Bar
         check_assist(
             introduce_named_generic,
             r#"fn foo<B>(bar: $0impl Bar) {}"#,
-            r#"fn foo<B, $0B0: Bar>(bar: B0) {}"#,
+            r#"fn foo<B, $0B1: Bar>(bar: B1) {}"#,
         );
     }
 
@@ -125,7 +136,7 @@ fn foo<$0B: Bar
         check_assist(
             introduce_named_generic,
             r#"fn foo<B, B0, B1, B3>(bar: $0impl Bar) {}"#,
-            r#"fn foo<B, B0, B1, B3, $0B2: Bar>(bar: B2) {}"#,
+            r#"fn foo<B, B0, B1, B3, $0B4: Bar>(bar: B4) {}"#,
         );
     }
 

src/tools/rust-analyzer/crates/ide-completion/src/completions/pattern.rs

@@ -48,11 +48,12 @@ pub(crate) fn complete_pattern(
 
     // Suggest name only in let-stmt and fn param
     if pattern_ctx.should_suggest_name {
+        let mut name_generator = suggest_name::NameGenerator::new();
         if let Some(suggested) = ctx
             .expected_type
             .as_ref()
             .map(|ty| ty.strip_references())
-            .and_then(|ty| suggest_name::for_type(&ty, ctx.db, ctx.edition))
+            .and_then(|ty| name_generator.for_type(&ty, ctx.db, ctx.edition))
         {
             acc.suggest_name(ctx, &suggested);
         }