From e4756cb4f6e66097638b9d101589358976be2ba8 Mon Sep 17 00:00:00 2001
From: Chetan Khilosiya <chetan.khilosiya@gmail.com>
Date: Tue, 23 Feb 2021 00:17:48 +0530
Subject: 7526: Rename crate assists to ide_assists.

---
 .../handlers/generate_default_from_enum_variant.rs | 175 +++++++++++++++++++++
 1 file changed, 175 insertions(+)
 create mode 100644 crates/ide_assists/src/handlers/generate_default_from_enum_variant.rs

(limited to 'crates/ide_assists/src/handlers/generate_default_from_enum_variant.rs')

diff --git a/crates/ide_assists/src/handlers/generate_default_from_enum_variant.rs b/crates/ide_assists/src/handlers/generate_default_from_enum_variant.rs
new file mode 100644
index 000000000..6a2ab9596
--- /dev/null
+++ b/crates/ide_assists/src/handlers/generate_default_from_enum_variant.rs
@@ -0,0 +1,175 @@
+use ide_db::helpers::FamousDefs;
+use ide_db::RootDatabase;
+use syntax::ast::{self, AstNode, NameOwner};
+use test_utils::mark;
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: generate_default_from_enum_variant
+//
+// Adds a Default impl for an enum using a variant.
+//
+// ```
+// enum Version {
+//  Undefined,
+//  Minor$0,
+//  Major,
+// }
+// ```
+// ->
+// ```
+// enum Version {
+//  Undefined,
+//  Minor,
+//  Major,
+// }
+//
+// impl Default for Version {
+//     fn default() -> Self {
+//         Self::Minor
+//     }
+// }
+// ```
+pub(crate) fn generate_default_from_enum_variant(
+    acc: &mut Assists,
+    ctx: &AssistContext,
+) -> Option<()> {
+    let variant = ctx.find_node_at_offset::<ast::Variant>()?;
+    let variant_name = variant.name()?;
+    let enum_name = variant.parent_enum().name()?;
+    if !matches!(variant.kind(), ast::StructKind::Unit) {
+        mark::hit!(test_gen_default_on_non_unit_variant_not_implemented);
+        return None;
+    }
+
+    if existing_default_impl(&ctx.sema, &variant).is_some() {
+        mark::hit!(test_gen_default_impl_already_exists);
+        return None;
+    }
+
+    let target = variant.syntax().text_range();
+    acc.add(
+        AssistId("generate_default_from_enum_variant", AssistKind::Generate),
+        "Generate `Default` impl from this enum variant",
+        target,
+        |edit| {
+            let start_offset = variant.parent_enum().syntax().text_range().end();
+            let buf = format!(
+                r#"
+
+impl Default for {0} {{
+    fn default() -> Self {{
+        Self::{1}
+    }}
+}}"#,
+                enum_name, variant_name
+            );
+            edit.insert(start_offset, buf);
+        },
+    )
+}
+
+fn existing_default_impl(
+    sema: &'_ hir::Semantics<'_, RootDatabase>,
+    variant: &ast::Variant,
+) -> Option<()> {
+    let variant = sema.to_def(variant)?;
+    let enum_ = variant.parent_enum(sema.db);
+    let krate = enum_.module(sema.db).krate();
+
+    let default_trait = FamousDefs(sema, Some(krate)).core_default_Default()?;
+    let enum_type = enum_.ty(sema.db);
+
+    if enum_type.impls_trait(sema.db, default_trait, &[]) {
+        Some(())
+    } else {
+        None
+    }
+}
+
+#[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) {
+        let fixture =
+            format!("//- /main.rs crate:main deps:core\n{}\n{}", ra_fixture, FamousDefs::FIXTURE);
+        check_assist_not_applicable(generate_default_from_enum_variant, &fixture)
+    }
+
+    #[test]
+    fn test_generate_default_from_variant() {
+        check_assist(
+            generate_default_from_enum_variant,
+            r#"
+enum Variant {
+    Undefined,
+    Minor$0,
+    Major,
+}"#,
+            r#"enum Variant {
+    Undefined,
+    Minor,
+    Major,
+}
+
+impl Default for Variant {
+    fn default() -> Self {
+        Self::Minor
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_default_already_implemented() {
+        mark::check!(test_gen_default_impl_already_exists);
+        check_not_applicable(
+            r#"
+enum Variant {
+    Undefined,
+    Minor$0,
+    Major,
+}
+
+impl Default for Variant {
+    fn default() -> Self {
+        Self::Minor
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_add_from_impl_no_element() {
+        mark::check!(test_gen_default_on_non_unit_variant_not_implemented);
+        check_not_applicable(
+            r#"
+enum Variant {
+    Undefined,
+    Minor(u32)$0,
+    Major,
+}"#,
+        );
+    }
+
+    #[test]
+    fn test_generate_default_from_variant_with_one_variant() {
+        check_assist(
+            generate_default_from_enum_variant,
+            r#"enum Variant { Undefi$0ned }"#,
+            r#"
+enum Variant { Undefined }
+
+impl Default for Variant {
+    fn default() -> Self {
+        Self::Undefined
+    }
+}"#,
+        );
+    }
+}
-- 
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