Rollup merge of #133424 - Nadrieril:guard-patterns-parsing, r=fee1-dead

Parse guard patterns

This implements the parsing of [RFC3637 Guard Patterns](https://rust-lang.github.io/rfcs/3637-guard-patterns.html) (see also [tracking issue](https://github.com/rust-lang/rust/issues/129967)). This PR is extracted from https://github.com/rust-lang/rust/pull/129996 with minor modifications.

cc `@max-niederman`

3 files changed, 17 insertions, 3 deletions

diff --git a/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs b/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs
index 9d26bf930a1..50a97579df7 100644
--- a/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs
+++ b/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs
@@ -234,7 +234,7 @@ fn transform_with_focus_on_idx(alternatives: &mut ThinVec<P<Pat>>, focus_idx: us
         // In the case of only two patterns, replacement adds net characters.
         | Ref(_, Mutability::Not)
         // Dealt with elsewhere.
-        | Or(_) | Paren(_) | Deref(_) => false,
+        | Or(_) | Paren(_) | Deref(_) | Guard(..) => false,
         // Transform `box x | ... | box y` into `box (x | y)`.
         //
         // The cases below until `Slice(...)` deal with *singleton* products.
diff --git a/src/tools/rustfmt/src/patterns.rs b/src/tools/rustfmt/src/patterns.rs
index 6fe2d4a8520..7b4730eadc8 100644
--- a/src/tools/rustfmt/src/patterns.rs
+++ b/src/tools/rustfmt/src/patterns.rs
@@ -48,7 +48,8 @@ fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
         | ast::PatKind::MacCall(..)
         | ast::PatKind::Slice(..)
         | ast::PatKind::Path(..)
-        | ast::PatKind::Range(..) => false,
+        | ast::PatKind::Range(..)
+        | ast::PatKind::Guard(..) => false,
         ast::PatKind::Tuple(ref subpats) => subpats.len() <= 1,
         ast::PatKind::TupleStruct(_, ref path, ref subpats) => {
             path.segments.len() <= 1 && subpats.len() <= 1
@@ -338,8 +339,9 @@ impl Rewrite for Pat {
                         .max_width_error(shape.width, self.span)?,
                 )
                 .map(|inner_pat| format!("({})", inner_pat)),
-            PatKind::Err(_) => Err(RewriteError::Unknown),
+            PatKind::Guard(..) => Ok(context.snippet(self.span).to_string()),
             PatKind::Deref(_) => Err(RewriteError::Unknown),
+            PatKind::Err(_) => Err(RewriteError::Unknown),
         }
     }
 }
diff --git a/src/tools/rustfmt/tests/target/guard_patterns.rs b/src/tools/rustfmt/tests/target/guard_patterns.rs
new file mode 100644
index 00000000000..2e4667b916c
--- /dev/null
+++ b/src/tools/rustfmt/tests/target/guard_patterns.rs
@@ -0,0 +1,12 @@
+#![feature(guard_patterns)]
+
+fn main() {
+    match user.subscription_plan() {
+        (Plan::Regular if user.credit() >= 100) | (Plan::Premium if user.credit() >= 80) => {
+            // Complete the transaction.
+        }
+        _ => {
+            // The user doesn't have enough credit, return an error message.
+        }
+    }
+}