add guard patterns to HIR and implement lowering

2 files changed, 9 insertions, 2 deletions

diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 5ea3bcef9ba..21367e0acbc 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1385,7 +1385,7 @@ impl<'hir> Pat<'hir> {
         use PatKind::*;
         match self.kind {
             Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => true,
-            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
+            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) | Guard(s, _) => s.walk_short_(it),
             Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
             Slice(before, slice, after) => {
@@ -1412,7 +1412,7 @@ impl<'hir> Pat<'hir> {
         use PatKind::*;
         match self.kind {
             Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => {}
-            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
+            Box(s) | Deref(s) | Ref(s, _) | Binding(.., Some(s)) | Guard(s, _) => s.walk_(it),
             Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
             Slice(before, slice, after) => {
@@ -1564,6 +1564,9 @@ pub enum PatKind<'hir> {
     /// A literal.
     Lit(&'hir Expr<'hir>),
 
+    /// A guard pattern (e.g., `x if guard(x)`).
+    Guard(&'hir Pat<'hir>, &'hir Expr<'hir>),
+
     /// A range pattern (e.g., `1..=2` or `1..2`).
     Range(Option<&'hir Expr<'hir>>, Option<&'hir Expr<'hir>>, RangeEnd),
 
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index 387a195cb29..be73b513db2 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -696,6 +696,10 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) -> V:
             visit_opt!(visitor, visit_pat, slice_pattern);
             walk_list!(visitor, visit_pat, postpatterns);
         }
+        PatKind::Guard(subpat, condition) => {
+            try_visit!(visitor.visit_pat(subpat));
+            try_visit!(visitor.visit_expr(condition));
+        }
     }
     V::Result::output()
 }