Exhaustively handle expressions in patterns

compiler/rustc_hir/src/hir.rs

@@ -1519,6 +1519,26 @@ impl fmt::Debug for DotDotPos {
     }
 }
 
+#[derive(Debug, Clone, Copy, HashStable_Generic)]
+pub struct PatExpr<'hir> {
+    pub hir_id: HirId,
+    pub span: Span,
+    pub kind: PatExprKind<'hir>,
+}
+
+#[derive(Debug, Clone, Copy, HashStable_Generic)]
+pub enum PatExprKind<'hir> {
+    Lit {
+        lit: &'hir Lit,
+        // FIXME: move this into `Lit` and handle negated literal expressions
+        // once instead of matching on unop neg expressions everywhere.
+        negated: bool,
+    },
+    ConstBlock(ConstBlock),
+    /// A path pattern for a unit struct/variant or a (maybe-associated) constant.
+    Path(QPath<'hir>),
+}
+
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub enum PatKind<'hir> {
     /// Represents a wildcard pattern (i.e., `_`).
@@ -1564,13 +1584,13 @@ pub enum PatKind<'hir> {
     Ref(&'hir Pat<'hir>, Mutability),
 
     /// A literal.
-    Lit(&'hir Expr<'hir>),
+    Lit(&'hir PatExpr<'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),
+    Range(Option<&'hir PatExpr<'hir>>, Option<&'hir PatExpr<'hir>>, RangeEnd),
 
     /// A slice pattern, `[before_0, ..., before_n, (slice, after_0, ..., after_n)?]`.
     ///
@@ -4144,6 +4164,10 @@ pub enum Node<'hir> {
     OpaqueTy(&'hir OpaqueTy<'hir>),
     Pat(&'hir Pat<'hir>),
     PatField(&'hir PatField<'hir>),
+    /// Needed as its own node with its own HirId for tracking
+    /// the unadjusted type of literals within patterns
+    /// (e.g. byte str literals not being of slice type).
+    PatExpr(&'hir PatExpr<'hir>),
     Arm(&'hir Arm<'hir>),
     Block(&'hir Block<'hir>),
     LetStmt(&'hir LetStmt<'hir>),
@@ -4200,6 +4224,7 @@ impl<'hir> Node<'hir> {
             | Node::Block(..)
             | Node::Ctor(..)
             | Node::Pat(..)
+            | Node::PatExpr(..)
             | Node::Arm(..)
             | Node::LetStmt(..)
             | Node::Crate(..)