Merge #7677

7677: More enum matching r=yoshuawuyts a=jDomantas

* Renamed existing `generate_enum_match_method` to `generate_enum_is_variant`
* Added two similar assists to generate `into_` and `as_` methods.
* Made all of them general enough to work on record and tuple variants too.

For `as_` method generation there's room to improve:
* Right now it always returns `Option<&Field>`, even though `Option<Field>` would be nicer when `Field: Copy`. I don't know how to check if the field type implements `Copy`. If given suggestions I could try to fix this in a follow-up pr.
* `&String` could be replaced with `&str`, `&Box<_>` with `&_`, and probably some more. I don't know what would be a good way to do that.

Closes #7604

Co-authored-by: Domantas Jadenkus <djadenkus@gmail.com>

Author: bors[bot]

crates/ide_assists/src/handlers/generate_enum_match_method.rs renamed to crates/ide_assists/src/handlers/generate_enum_is_method.rs

@@ -1,14 +1,13 @@
-use stdx::{format_to, to_lower_snake_case};
+use stdx::to_lower_snake_case;
 use syntax::ast::VisibilityOwner;
 use syntax::ast::{self, AstNode, NameOwner};
-use test_utils::mark;
 
 use crate::{
-    utils::{find_impl_block_end, find_struct_impl, generate_impl_text},
+    utils::{add_method_to_adt, find_struct_impl},
     AssistContext, AssistId, AssistKind, Assists,
 };
 
-// Assist: generate_enum_match_method
+// Assist: generate_enum_is_method
 //
 // Generate an `is_` method for an enum variant.
 //
@@ -34,79 +33,52 @@ use crate::{
 //     }
 // }
 // ```
-pub(crate) fn generate_enum_match_method(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+pub(crate) fn generate_enum_is_method(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let variant = ctx.find_node_at_offset::<ast::Variant>()?;
     let variant_name = variant.name()?;
-    let parent_enum = variant.parent_enum();
-    if !matches!(variant.kind(), ast::StructKind::Unit) {
-        mark::hit!(test_gen_enum_match_on_non_unit_variant_not_implemented);
-        return None;
-    }
+    let parent_enum = ast::Adt::Enum(variant.parent_enum());
+    let pattern_suffix = match variant.kind() {
+        ast::StructKind::Record(_) => " { .. }",
+        ast::StructKind::Tuple(_) => "(..)",
+        ast::StructKind::Unit => "",
+    };
 
     let enum_lowercase_name = to_lower_snake_case(&parent_enum.name()?.to_string());
-    let fn_name = to_lower_snake_case(&variant_name.to_string());
+    let fn_name = format!("is_{}", &to_lower_snake_case(variant_name.text()));
 
     // Return early if we've found an existing new fn
-    let impl_def = find_struct_impl(
-        &ctx,
-        &ast::Adt::Enum(parent_enum.clone()),
-        format!("is_{}", fn_name).as_str(),
-    )?;
+    let impl_def = find_struct_impl(&ctx, &parent_enum, &fn_name)?;
 
     let target = variant.syntax().text_range();
     acc.add(
-        AssistId("generate_enum_match_method", AssistKind::Generate),
+        AssistId("generate_enum_is_method", AssistKind::Generate),
         "Generate an `is_` method for an enum variant",
         target,
         |builder| {
-            let mut buf = String::with_capacity(512);
-
-            if impl_def.is_some() {
-                buf.push('\n');
-            }
-
             let vis = parent_enum.visibility().map_or(String::new(), |v| format!("{} ", v));
-            format_to!(
-                buf,
+            let method = format!(
                 "    /// Returns `true` if the {} is [`{}`].
-    {}fn is_{}(&self) -> bool {{
-        matches!(self, Self::{})
+    {}fn {}(&self) -> bool {{
+        matches!(self, Self::{}{})
     }}",
-                enum_lowercase_name,
-                variant_name,
-                vis,
-                fn_name,
-                variant_name
+                enum_lowercase_name, variant_name, vis, fn_name, variant_name, pattern_suffix,
             );
 
-            let start_offset = impl_def
-                .and_then(|impl_def| find_impl_block_end(impl_def, &mut buf))
-                .unwrap_or_else(|| {
-                    buf = generate_impl_text(&ast::Adt::Enum(parent_enum.clone()), &buf);
-                    parent_enum.syntax().text_range().end()
-                });
-
-            builder.insert(start_offset, buf);
+            add_method_to_adt(builder, &parent_enum, impl_def, &method);
         },
     )
 }
 
 #[cfg(test)]
 mod tests {
-    use test_utils::mark;
-
     use crate::tests::{check_assist, check_assist_not_applicable};
 
     use super::*;
 
-    fn check_not_applicable(ra_fixture: &str) {
-        check_assist_not_applicable(generate_enum_match_method, ra_fixture)
-    }
-
     #[test]
-    fn test_generate_enum_match_from_variant() {
+    fn test_generate_enum_is_from_variant() {
         check_assist(
-            generate_enum_match_method,
+            generate_enum_is_method,
             r#"
 enum Variant {
     Undefined,
@@ -129,8 +101,9 @@ impl Variant {
     }
 
     #[test]
-    fn test_generate_enum_match_already_implemented() {
-        check_not_applicable(
+    fn test_generate_enum_is_already_implemented() {
+        check_assist_not_applicable(
+            generate_enum_is_method,
             r#"
 enum Variant {
     Undefined,
@@ -147,22 +120,59 @@ impl Variant {
     }
 
     #[test]
-    fn test_add_from_impl_no_element() {
-        mark::check!(test_gen_enum_match_on_non_unit_variant_not_implemented);
-        check_not_applicable(
+    fn test_generate_enum_is_from_tuple_variant() {
+        check_assist(
+            generate_enum_is_method,
             r#"
 enum Variant {
     Undefined,
     Minor(u32)$0,
     Major,
+}"#,
+            r#"enum Variant {
+    Undefined,
+    Minor(u32),
+    Major,
+}
+
+impl Variant {
+    /// Returns `true` if the variant is [`Minor`].
+    fn is_minor(&self) -> bool {
+        matches!(self, Self::Minor(..))
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_enum_is_from_record_variant() {
+        check_assist(
+            generate_enum_is_method,
+            r#"
+enum Variant {
+    Undefined,
+    Minor { foo: i32 }$0,
+    Major,
+}"#,
+            r#"enum Variant {
+    Undefined,
+    Minor { foo: i32 },
+    Major,
+}
+
+impl Variant {
+    /// Returns `true` if the variant is [`Minor`].
+    fn is_minor(&self) -> bool {
+        matches!(self, Self::Minor { .. })
+    }
 }"#,
         );
     }
 
     #[test]
-    fn test_generate_enum_match_from_variant_with_one_variant() {
+    fn test_generate_enum_is_from_variant_with_one_variant() {
         check_assist(
-            generate_enum_match_method,
+            generate_enum_is_method,
             r#"enum Variant { Undefi$0ned }"#,
             r#"
 enum Variant { Undefined }
@@ -177,9 +187,9 @@ impl Variant {
     }
 
     #[test]
-    fn test_generate_enum_match_from_variant_with_visibility_marker() {
+    fn test_generate_enum_is_from_variant_with_visibility_marker() {
         check_assist(
-            generate_enum_match_method,
+            generate_enum_is_method,
             r#"
 pub(crate) enum Variant {
     Undefined,
@@ -202,9 +212,9 @@ impl Variant {
     }
 
     #[test]
-    fn test_multiple_generate_enum_match_from_variant() {
+    fn test_multiple_generate_enum_is_from_variant() {
         check_assist(
-            generate_enum_match_method,
+            generate_enum_is_method,
             r#"
 enum Variant {
     Undefined,