1 files changed, 150 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/ide-assists/src/handlers/replace_try_expr_with_match.rs b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/replace_try_expr_with_match.rs
new file mode 100644
index 000000000..38fccb338
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/replace_try_expr_with_match.rs
@@ -0,0 +1,150 @@
+use std::iter;
+
+use ide_db::{
+    assists::{AssistId, AssistKind},
+    ty_filter::TryEnum,
+};
+use syntax::{
+    ast::{
+        self,
+        edit::{AstNodeEdit, IndentLevel},
+        make,
+    },
+    AstNode, T,
+};
+
+use crate::assist_context::{AssistContext, Assists};
+
+// Assist: replace_try_expr_with_match
+//
+// Replaces a `try` expression with a `match` expression.
+//
+// ```
+// # //- minicore:option
+// fn handle() {
+//     let pat = Some(true)$0?;
+// }
+// ```
+// ->
+// ```
+// fn handle() {
+//     let pat = match Some(true) {
+//         Some(it) => it,
+//         None => return None,
+//     };
+// }
+// ```
+pub(crate) fn replace_try_expr_with_match(
+    acc: &mut Assists,
+    ctx: &AssistContext<'_>,
+) -> Option<()> {
+    let qm_kw = ctx.find_token_syntax_at_offset(T![?])?;
+    let qm_kw_parent = qm_kw.parent().and_then(ast::TryExpr::cast)?;
+
+    let expr = qm_kw_parent.expr()?;
+    let expr_type_info = ctx.sema.type_of_expr(&expr)?;
+
+    let try_enum = TryEnum::from_ty(&ctx.sema, &expr_type_info.original)?;
+
+    let target = qm_kw_parent.syntax().text_range();
+    acc.add(
+        AssistId("replace_try_expr_with_match", AssistKind::RefactorRewrite),
+        "Replace try expression with match",
+        target,
+        |edit| {
+            let sad_pat = match try_enum {
+                TryEnum::Option => make::path_pat(make::ext::ident_path("None")),
+                TryEnum::Result => make::tuple_struct_pat(
+                    make::ext::ident_path("Err"),
+                    iter::once(make::path_pat(make::ext::ident_path("err"))),
+                )
+                .into(),
+            };
+            let sad_expr = match try_enum {
+                TryEnum::Option => {
+                    make::expr_return(Some(make::expr_path(make::ext::ident_path("None"))))
+                }
+                TryEnum::Result => make::expr_return(Some(make::expr_call(
+                    make::expr_path(make::ext::ident_path("Err")),
+                    make::arg_list(iter::once(make::expr_path(make::ext::ident_path("err")))),
+                ))),
+            };
+
+            let happy_arm = make::match_arm(
+                iter::once(
+                    try_enum.happy_pattern(make::ident_pat(false, false, make::name("it")).into()),
+                ),
+                None,
+                make::expr_path(make::ext::ident_path("it")),
+            );
+            let sad_arm = make::match_arm(iter::once(sad_pat), None, sad_expr);
+
+            let match_arm_list = make::match_arm_list([happy_arm, sad_arm]);
+
+            let expr_match = make::expr_match(expr, match_arm_list)
+                .indent(IndentLevel::from_node(qm_kw_parent.syntax()));
+            edit.replace_ast::<ast::Expr>(qm_kw_parent.into(), expr_match);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    #[test]
+    fn test_replace_try_expr_with_match_not_applicable() {
+        check_assist_not_applicable(
+            replace_try_expr_with_match,
+            r#"
+                fn test() {
+                    let pat: u32 = 25$0;
+                }
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_replace_try_expr_with_match_option() {
+        check_assist(
+            replace_try_expr_with_match,
+            r#"
+//- minicore:option
+fn test() {
+    let pat = Some(true)$0?;
+}
+            "#,
+            r#"
+fn test() {
+    let pat = match Some(true) {
+        Some(it) => it,
+        None => return None,
+    };
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_replace_try_expr_with_match_result() {
+        check_assist(
+            replace_try_expr_with_match,
+            r#"
+//- minicore:result
+fn test() {
+    let pat = Ok(true)$0?;
+}
+            "#,
+            r#"
+fn test() {
+    let pat = match Ok(true) {
+        Ok(it) => it,
+        Err(err) => return Err(err),
+    };
+}
+            "#,
+        );
+    }
+}