internal: Generally improve make::match_arm

`make::match_arm` should take a single `ast::Pat`, and callers can handle creating an `ast::OrPat` if need be. It should also take a proper `ast::MatchGuard`, instead of making one itself.

Author: Giga-Bowser

crates/ide-assists/src/handlers/add_missing_match_arms.rs

@@ -212,8 +212,7 @@ pub(crate) fn add_missing_match_arms(acc: &mut Assists, ctx: &AssistContext<'_>)
                     !hidden
                 })
                 .map(|(pat, _)| {
-                    make::match_arm(iter::once(pat), None, make::ext::expr_todo())
-                        .clone_for_update()
+                    make::match_arm(pat, None, make::ext::expr_todo()).clone_for_update()
                 });
 
             let catch_all_arm = new_match_arm_list
@@ -243,12 +242,9 @@ pub(crate) fn add_missing_match_arms(acc: &mut Assists, ctx: &AssistContext<'_>)
 
             if needs_catch_all_arm && !has_catch_all_arm {
                 cov_mark::hit!(added_wildcard_pattern);
-                let arm = make::match_arm(
-                    iter::once(make::wildcard_pat().into()),
-                    None,
-                    make::ext::expr_todo(),
-                )
-                .clone_for_update();
+                let arm =
+                    make::match_arm(make::wildcard_pat().into(), None, make::ext::expr_todo())
+                        .clone_for_update();
                 todo_placeholders.push(arm.expr().unwrap());
                 added_arms.push(arm);
             }

crates/ide-assists/src/handlers/extract_function.rs

@@ -1554,12 +1554,12 @@ impl FlowHandler {
                     let value_pat = make::ext::simple_ident_pat(make::name(some_name));
                     let pat = make::tuple_struct_pat(path, iter::once(value_pat.into()));
                     let value = make::expr_path(make::ext::ident_path(some_name));
-                    make::match_arm(iter::once(pat.into()), None, value)
+                    make::match_arm(pat.into(), None, value)
                 };
                 let none_arm = {
                     let path = make::ext::ident_path("None");
                     let pat = make::path_pat(path);
-                    make::match_arm(iter::once(pat), None, none.make_result_handler(None))
+                    make::match_arm(pat, None, none.make_result_handler(None))
                 };
                 let arms = make::match_arm_list(vec![some_arm, none_arm]);
                 make::expr_match(call_expr, arms)
@@ -1573,18 +1573,14 @@ impl FlowHandler {
                     let value_pat = make::ext::simple_ident_pat(make::name(ok_name));
                     let pat = make::tuple_struct_pat(path, iter::once(value_pat.into()));
                     let value = make::expr_path(make::ext::ident_path(ok_name));
-                    make::match_arm(iter::once(pat.into()), None, value)
+                    make::match_arm(pat.into(), None, value)
                 };
                 let err_arm = {
                     let path = make::ext::ident_path("Err");
                     let value_pat = make::ext::simple_ident_pat(make::name(err_name));
                     let pat = make::tuple_struct_pat(path, iter::once(value_pat.into()));
                     let value = make::expr_path(make::ext::ident_path(err_name));
-                    make::match_arm(
-                        iter::once(pat.into()),
-                        None,
-                        err.make_result_handler(Some(value)),
-                    )
+                    make::match_arm(pat.into(), None, err.make_result_handler(Some(value)))
                 };
                 let arms = make::match_arm_list(vec![ok_arm, err_arm]);
                 make::expr_match(call_expr, arms)

crates/ide-assists/src/handlers/replace_if_let_with_match.rs

@@ -114,17 +114,15 @@ pub(crate) fn replace_if_let_with_match(acc: &mut Assists, ctx: &AssistContext<'
                 let make_match_arm = |(pat, body): (_, ast::BlockExpr)| {
                     let body = body.reset_indent().indent(IndentLevel(1));
                     match pat {
-                        Either::Left(pat) => {
-                            make::match_arm(iter::once(pat), None, unwrap_trivial_block(body))
-                        }
+                        Either::Left(pat) => make::match_arm(pat, None, unwrap_trivial_block(body)),
                         Either::Right(_) if !pat_seen => make::match_arm(
-                            iter::once(make::literal_pat("true").into()),
+                            make::literal_pat("true").into(),
                             None,
                             unwrap_trivial_block(body),
                         ),
                         Either::Right(expr) => make::match_arm(
-                            iter::once(make::wildcard_pat().into()),
-                            Some(expr),
+                            make::wildcard_pat().into(),
+                            Some(make::match_guard(expr)),
                             unwrap_trivial_block(body),
                         ),
                     }
@@ -181,7 +179,7 @@ fn make_else_arm(
         };
         (pattern, make::ext::expr_unit())
     };
-    make::match_arm(iter::once(pattern), None, expr)
+    make::match_arm(pattern, None, expr)
 }
 
 // Assist: replace_match_with_if_let

crates/ide-assists/src/handlers/replace_try_expr_with_match.rs

@@ -71,13 +71,11 @@ pub(crate) fn replace_try_expr_with_match(
             };
 
             let happy_arm = make::match_arm(
-                iter::once(
-                    try_enum.happy_pattern(make::ident_pat(false, false, make::name("it")).into()),
-                ),
+                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 sad_arm = make::match_arm(sad_pat, None, sad_expr);
 
             let match_arm_list = make::match_arm_list([happy_arm, sad_arm]);
 

crates/ide-assists/src/handlers/unmerge_match_arm.rs

@@ -54,13 +54,9 @@ pub(crate) fn unmerge_match_arm(acc: &mut Assists, ctx: &AssistContext<'_>) -> O
             let pats_after = pipe_token
                 .siblings_with_tokens(Direction::Next)
                 .filter_map(|it| ast::Pat::cast(it.into_node()?));
-            // FIXME: We should add a leading pipe if the original arm has one.
-            let new_match_arm = make::match_arm(
-                pats_after,
-                match_arm.guard().and_then(|guard| guard.condition()),
-                match_arm_body,
-            )
-            .clone_for_update();
+            let new_pat = make::or_pat(pats_after, or_pat.leading_pipe().is_some());
+            let new_match_arm =
+                make::match_arm(new_pat, match_arm.guard(), match_arm_body).clone_for_update();
 
             let mut pipe_index = pipe_token.index();
             if pipe_token

crates/ide-assists/src/utils/gen_trait_fn_body.rs

@@ -66,7 +66,7 @@ fn gen_clone_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
                         let pat = make::record_pat(variant_name.clone(), pats.into_iter());
                         let fields = make::record_expr_field_list(fields);
                         let record_expr = make::record_expr(variant_name, fields).into();
-                        arms.push(make::match_arm(Some(pat.into()), None, record_expr));
+                        arms.push(make::match_arm(pat.into(), None, record_expr));
                     }
 
                     // => match self { Self::Name(arg1) => Self::Name(arg1.clone()) }
@@ -84,14 +84,14 @@ fn gen_clone_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
                         let pat = make::tuple_struct_pat(variant_name.clone(), pats.into_iter());
                         let struct_name = make::expr_path(variant_name);
                         let tuple_expr = make::expr_call(struct_name, make::arg_list(fields));
-                        arms.push(make::match_arm(Some(pat.into()), None, tuple_expr));
+                        arms.push(make::match_arm(pat.into(), None, tuple_expr));
                     }
 
                     // => match self { Self::Name => Self::Name }
                     None => {
                         let pattern = make::path_pat(variant_name.clone());
                         let variant_expr = make::expr_path(variant_name);
-                        arms.push(make::match_arm(Some(pattern), None, variant_expr));
+                        arms.push(make::match_arm(pattern, None, variant_expr));
                     }
                 }
             }
@@ -190,7 +190,7 @@ fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
 
                         // => MyStruct { fields.. } => f.debug_struct("MyStruct")...finish(),
                         let pat = make::record_pat(variant_name.clone(), pats.into_iter());
-                        arms.push(make::match_arm(Some(pat.into()), None, expr));
+                        arms.push(make::match_arm(pat.into(), None, expr));
                     }
                     Some(ast::FieldList::TupleFieldList(list)) => {
                         // => f.debug_tuple(name)
@@ -223,7 +223,7 @@ fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
 
                         // => MyStruct (fields..) => f.debug_tuple("MyStruct")...finish(),
                         let pat = make::tuple_struct_pat(variant_name.clone(), pats.into_iter());
-                        arms.push(make::match_arm(Some(pat.into()), None, expr));
+                        arms.push(make::match_arm(pat.into(), None, expr));
                     }
                     None => {
                         let fmt_string = make::expr_literal(&(format!("\"{name}\""))).into();
@@ -232,7 +232,7 @@ fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
                         let macro_call = make::expr_macro_call(macro_name, args);
 
                         let variant_name = make::path_pat(variant_name);
-                        arms.push(make::match_arm(Some(variant_name), None, macro_call));
+                        arms.push(make::match_arm(variant_name, None, macro_call));
                     }
                 }
             }
@@ -485,7 +485,7 @@ fn gen_partial_eq(adt: &ast::Adt, func: &ast::Fn, trait_ref: Option<TraitRef>) -
                         let tuple = make::tuple_pat(vec![left.into(), right.into()]);
 
                         if let Some(expr) = expr {
-                            arms.push(make::match_arm(Some(tuple.into()), None, expr));
+                            arms.push(make::match_arm(tuple.into(), None, expr));
                         }
                     }
 
@@ -518,7 +518,7 @@ fn gen_partial_eq(adt: &ast::Adt, func: &ast::Fn, trait_ref: Option<TraitRef>) -
                         let tuple = make::tuple_pat(vec![left.into(), right.into()]);
 
                         if let Some(expr) = expr {
-                            arms.push(make::match_arm(Some(tuple.into()), None, expr));
+                            arms.push(make::match_arm(tuple.into(), None, expr));
                         }
                     }
                     None => continue,
@@ -538,7 +538,7 @@ fn gen_partial_eq(adt: &ast::Adt, func: &ast::Fn, trait_ref: Option<TraitRef>) -
                         } else {
                             eq_check
                         };
-                        arms.push(make::match_arm(Some(lhs), None, rhs));
+                        arms.push(make::match_arm(lhs, None, rhs));
                     }
 
                     let match_target = make::expr_tuple([lhs_name, rhs_name]).into();
@@ -599,10 +599,10 @@ fn gen_partial_ord(adt: &ast::Adt, func: &ast::Fn, trait_ref: Option<TraitRef>)
         let variant_name =
             make::path_pat(make::ext::path_from_idents(["core", "cmp", "Ordering", "Equal"])?);
         let lhs = make::tuple_struct_pat(make::ext::path_from_idents(["Some"])?, [variant_name]);
-        arms.push(make::match_arm(Some(lhs.into()), None, make::expr_empty_block()));
+        arms.push(make::match_arm(lhs.into(), None, make::expr_empty_block()));
 
         arms.push(make::match_arm(
-            [make::ident_pat(false, false, make::name("ord")).into()],
+            make::ident_pat(false, false, make::name("ord")).into(),
             None,
             make::expr_return(Some(make::expr_path(make::ext::ident_path("ord")))),
         ));

crates/syntax/src/ast/edit.rs

@@ -153,8 +153,7 @@ impl<N: AstNode + Clone> AstNodeEdit for N {}
 #[test]
 fn test_increase_indent() {
     let arm_list = {
-        let arm =
-            make::match_arm(iter::once(make::wildcard_pat().into()), None, make::ext::expr_unit());
+        let arm = make::match_arm(make::wildcard_pat().into(), None, make::ext::expr_unit());
         make::match_arm_list([arm.clone(), arm])
     };
     assert_eq!(

crates/syntax/src/ast/make.rs

@@ -787,15 +787,21 @@ pub fn path_pat(path: ast::Path) -> ast::Pat {
     }
 }
 
-pub fn match_arm(
-    pats: impl IntoIterator<Item = ast::Pat>,
-    guard: Option<ast::Expr>,
-    expr: ast::Expr,
-) -> ast::MatchArm {
-    let pats_str = pats.into_iter().join(" | ");
+/// Returns a `Pat` if the path has just one segment, an `OrPat` otherwise.
+pub fn or_pat(pats: impl IntoIterator<Item = ast::Pat>, leading_pipe: bool) -> ast::Pat {
+    let leading_pipe = if leading_pipe { "| " } else { "" };
+    let pats = pats.into_iter().join(" | ");
+
+    return from_text(&format!("{leading_pipe}{pats}"));
+    fn from_text(text: &str) -> ast::Pat {
+        ast_from_text(&format!("fn f({text}: ())"))
+    }
+}
+
+pub fn match_arm(pat: ast::Pat, guard: Option<ast::MatchGuard>, expr: ast::Expr) -> ast::MatchArm {
     return match guard {
-        Some(guard) => from_text(&format!("{pats_str} if {guard} => {expr}")),
-        None => from_text(&format!("{pats_str} => {expr}")),
+        Some(guard) => from_text(&format!("{pat} {guard} => {expr}")),
+        None => from_text(&format!("{pat} => {expr}")),
     };
 
     fn from_text(text: &str) -> ast::MatchArm {
@@ -816,6 +822,14 @@ pub fn match_arm_with_guard(
     }
 }
 
+pub fn match_guard(condition: ast::Expr) -> ast::MatchGuard {
+    return from_text(&format!("if {condition}"));
+
+    fn from_text(text: &str) -> ast::MatchGuard {
+        ast_from_text(&format!("fn f() {{ match () {{() {text} => () }}"))
+    }
+}
+
 pub fn match_arm_list(arms: impl IntoIterator<Item = ast::MatchArm>) -> ast::MatchArmList {
     let arms_str = arms.into_iter().fold(String::new(), |mut acc, arm| {
         let needs_comma = arm.expr().is_none_or(|it| !it.is_block_like());

crates/syntax/src/syntax_editor.rs

@@ -335,7 +335,7 @@ mod tests {
     #[test]
     fn basic_usage() {
         let root = make::match_arm(
-            [make::wildcard_pat().into()],
+            make::wildcard_pat().into(),
             None,
             make::expr_tuple([
                 make::expr_bin_op(