Rollup merge of #135251 - oli-obk:push-lmpyvvyrtplk, r=ytmimi

Only treat plain literal patterns as short

See https://github.com/rust-lang/rust/pull/134228#discussion_r1905848384 and https://github.com/rust-lang/rust/pull/134228#discussion_r1905916702 for context. We never wanted to treat const blocks and paths as short, only plain literals.

I don't know how to write a test for this, it.s not clear to me how the short pattern check actually affects the formatting

src/tools/rustfmt/src/patterns.rs

@@ -31,18 +31,31 @@ use crate::utils::{format_mutability, mk_sp, mk_sp_lo_plus_one, rewrite_ident};
 ///     - `[small, ntp]`
 ///     - unary tuple constructor `([small, ntp])`
 ///     - `&[small]`
-pub(crate) fn is_short_pattern(pat: &ast::Pat, pat_str: &str) -> bool {
+pub(crate) fn is_short_pattern(
+    context: &RewriteContext<'_>,
+    pat: &ast::Pat,
+    pat_str: &str,
+) -> bool {
     // We also require that the pattern is reasonably 'small' with its literal width.
-    pat_str.len() <= 20 && !pat_str.contains('\n') && is_short_pattern_inner(pat)
+    pat_str.len() <= 20 && !pat_str.contains('\n') && is_short_pattern_inner(context, pat)
 }
 
-fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
-    match pat.kind {
-        ast::PatKind::Rest
-        | ast::PatKind::Never
-        | ast::PatKind::Wild
-        | ast::PatKind::Err(_)
-        | ast::PatKind::Expr(_) => true,
+fn is_short_pattern_inner(context: &RewriteContext<'_>, pat: &ast::Pat) -> bool {
+    match &pat.kind {
+        ast::PatKind::Rest | ast::PatKind::Never | ast::PatKind::Wild | ast::PatKind::Err(_) => {
+            true
+        }
+        ast::PatKind::Expr(expr) => match &expr.kind {
+            ast::ExprKind::Lit(_) => true,
+            ast::ExprKind::Unary(ast::UnOp::Neg, expr) => match &expr.kind {
+                ast::ExprKind::Lit(_) => true,
+                _ => unreachable!(),
+            },
+            ast::ExprKind::ConstBlock(_) | ast::ExprKind::Path(..) => {
+                context.config.style_edition() <= StyleEdition::Edition2024
+            }
+            _ => unreachable!(),
+        },
         ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
         ast::PatKind::Struct(..)
         | ast::PatKind::MacCall(..)
@@ -57,8 +70,8 @@ fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
         ast::PatKind::Box(ref p)
         | PatKind::Deref(ref p)
         | ast::PatKind::Ref(ref p, _)
-        | ast::PatKind::Paren(ref p) => is_short_pattern_inner(&*p),
-        PatKind::Or(ref pats) => pats.iter().all(|p| is_short_pattern_inner(p)),
+        | ast::PatKind::Paren(ref p) => is_short_pattern_inner(context, &*p),
+        PatKind::Or(ref pats) => pats.iter().all(|p| is_short_pattern_inner(context, p)),
     }
 }
 
@@ -96,7 +109,7 @@ impl Rewrite for Pat {
                 let use_mixed_layout = pats
                     .iter()
                     .zip(pat_strs.iter())
-                    .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
+                    .all(|(pat, pat_str)| is_short_pattern(context, pat, pat_str));
                 let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
                 let tactic = if use_mixed_layout {
                     DefinitiveListTactic::Mixed

src/tools/rustfmt/tests/source/pattern.rs

@@ -88,3 +88,13 @@ fn issue3728() {
         | c;
     foo((1,));
 }
+
+fn literals() {
+    match 42 {
+        const { 1 + 2 } | 4
+        | 6 => {}
+        10 | 11 | 12
+        | 13 | 14 => {}
+        _ => {}
+    }
+}

src/tools/rustfmt/tests/target/pattern.rs

@@ -96,3 +96,11 @@ fn issue3728() {
     let foo = |(c,)| c;
     foo((1,));
 }
+
+fn literals() {
+    match 42 {
+        const { 1 + 2 } | 4 | 6 => {}
+        10 | 11 | 12 | 13 | 14 => {}
+        _ => {}
+    }
+}