1 files changed, 187 insertions, 0 deletions

diff --git a/crates/assists/src/handlers/replace_unwrap_with_match.rs b/crates/assists/src/handlers/replace_unwrap_with_match.rs
new file mode 100644
index 000000000..9705f11b7
--- /dev/null
+++ b/crates/assists/src/handlers/replace_unwrap_with_match.rs
@@ -0,0 +1,187 @@
+use std::iter;
+
+use syntax::{
+    ast::{
+        self,
+        edit::{AstNodeEdit, IndentLevel},
+        make,
+    },
+    AstNode,
+};
+
+use crate::{
+    utils::{render_snippet, Cursor, TryEnum},
+    AssistContext, AssistId, AssistKind, Assists,
+};
+
+// Assist: replace_unwrap_with_match
+//
+// Replaces `unwrap` a `match` expression. Works for Result and Option.
+//
+// ```
+// enum Result<T, E> { Ok(T), Err(E) }
+// fn main() {
+//     let x: Result<i32, i32> = Result::Ok(92);
+//     let y = x.<|>unwrap();
+// }
+// ```
+// ->
+// ```
+// enum Result<T, E> { Ok(T), Err(E) }
+// fn main() {
+//     let x: Result<i32, i32> = Result::Ok(92);
+//     let y = match x {
+//         Ok(a) => a,
+//         $0_ => unreachable!(),
+//     };
+// }
+// ```
+pub(crate) fn replace_unwrap_with_match(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let method_call: ast::MethodCallExpr = ctx.find_node_at_offset()?;
+    let name = method_call.name_ref()?;
+    if name.text() != "unwrap" {
+        return None;
+    }
+    let caller = method_call.expr()?;
+    let ty = ctx.sema.type_of_expr(&caller)?;
+    let happy_variant = TryEnum::from_ty(&ctx.sema, &ty)?.happy_case();
+    let target = method_call.syntax().text_range();
+    acc.add(
+        AssistId("replace_unwrap_with_match", AssistKind::RefactorRewrite),
+        "Replace unwrap with match",
+        target,
+        |builder| {
+            let ok_path = make::path_unqualified(make::path_segment(make::name_ref(happy_variant)));
+            let it = make::ident_pat(make::name("a")).into();
+            let ok_tuple = make::tuple_struct_pat(ok_path, iter::once(it)).into();
+
+            let bind_path = make::path_unqualified(make::path_segment(make::name_ref("a")));
+            let ok_arm = make::match_arm(iter::once(ok_tuple), make::expr_path(bind_path));
+
+            let unreachable_call = make::expr_unreachable();
+            let err_arm =
+                make::match_arm(iter::once(make::wildcard_pat().into()), unreachable_call);
+
+            let match_arm_list = make::match_arm_list(vec![ok_arm, err_arm]);
+            let match_expr = make::expr_match(caller.clone(), match_arm_list)
+                .indent(IndentLevel::from_node(method_call.syntax()));
+
+            let range = method_call.syntax().text_range();
+            match ctx.config.snippet_cap {
+                Some(cap) => {
+                    let err_arm = match_expr
+                        .syntax()
+                        .descendants()
+                        .filter_map(ast::MatchArm::cast)
+                        .last()
+                        .unwrap();
+                    let snippet =
+                        render_snippet(cap, match_expr.syntax(), Cursor::Before(err_arm.syntax()));
+                    builder.replace_snippet(cap, range, snippet)
+                }
+                None => builder.replace(range, match_expr.to_string()),
+            }
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_target};
+
+    use super::*;
+
+    #[test]
+    fn test_replace_result_unwrap_with_match() {
+        check_assist(
+            replace_unwrap_with_match,
+            r"
+enum Result<T, E> { Ok(T), Err(E) }
+fn i<T>(a: T) -> T { a }
+fn main() {
+    let x: Result<i32, i32> = Result::Ok(92);
+    let y = i(x).<|>unwrap();
+}
+            ",
+            r"
+enum Result<T, E> { Ok(T), Err(E) }
+fn i<T>(a: T) -> T { a }
+fn main() {
+    let x: Result<i32, i32> = Result::Ok(92);
+    let y = match i(x) {
+        Ok(a) => a,
+        $0_ => unreachable!(),
+    };
+}
+            ",
+        )
+    }
+
+    #[test]
+    fn test_replace_option_unwrap_with_match() {
+        check_assist(
+            replace_unwrap_with_match,
+            r"
+enum Option<T> { Some(T), None }
+fn i<T>(a: T) -> T { a }
+fn main() {
+    let x = Option::Some(92);
+    let y = i(x).<|>unwrap();
+}
+            ",
+            r"
+enum Option<T> { Some(T), None }
+fn i<T>(a: T) -> T { a }
+fn main() {
+    let x = Option::Some(92);
+    let y = match i(x) {
+        Some(a) => a,
+        $0_ => unreachable!(),
+    };
+}
+            ",
+        );
+    }
+
+    #[test]
+    fn test_replace_result_unwrap_with_match_chaining() {
+        check_assist(
+            replace_unwrap_with_match,
+            r"
+enum Result<T, E> { Ok(T), Err(E) }
+fn i<T>(a: T) -> T { a }
+fn main() {
+    let x: Result<i32, i32> = Result::Ok(92);
+    let y = i(x).<|>unwrap().count_zeroes();
+}
+            ",
+            r"
+enum Result<T, E> { Ok(T), Err(E) }
+fn i<T>(a: T) -> T { a }
+fn main() {
+    let x: Result<i32, i32> = Result::Ok(92);
+    let y = match i(x) {
+        Ok(a) => a,
+        $0_ => unreachable!(),
+    }.count_zeroes();
+}
+            ",
+        )
+    }
+
+    #[test]
+    fn replace_unwrap_with_match_target() {
+        check_assist_target(
+            replace_unwrap_with_match,
+            r"
+enum Option<T> { Some(T), None }
+fn i<T>(a: T) -> T { a }
+fn main() {
+    let x = Option::Some(92);
+    let y = i(x).<|>unwrap();
+}
+            ",
+            r"i(x).unwrap()",
+        );
+    }
+}