Auto merge of #112887 - WaffleLapkin:become_unuwuable_in_hir, r=compiler-errors,Nilstrieb

`hir`: Add `Become` expression kind (explicit tail calls experiment)

This adds `hir::ExprKind::Become` alongside ast lowering. During hir-thir lowering we currently lower `become` as `return`, so that we can partially test `become` without ICEing.

cc `@scottmcm`
r? `@Nilstrieb`

1 files changed, 5 insertions, 0 deletions

diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 5e5001bc8b4..591831b59a1 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1719,6 +1719,7 @@ impl Expr<'_> {
             ExprKind::Break(..) => ExprPrecedence::Break,
             ExprKind::Continue(..) => ExprPrecedence::Continue,
             ExprKind::Ret(..) => ExprPrecedence::Ret,
+            ExprKind::Become(..) => ExprPrecedence::Become,
             ExprKind::InlineAsm(..) => ExprPrecedence::InlineAsm,
             ExprKind::OffsetOf(..) => ExprPrecedence::OffsetOf,
             ExprKind::Struct(..) => ExprPrecedence::Struct,
@@ -1776,6 +1777,7 @@ impl Expr<'_> {
             | ExprKind::Break(..)
             | ExprKind::Continue(..)
             | ExprKind::Ret(..)
+            | ExprKind::Become(..)
             | ExprKind::Let(..)
             | ExprKind::Loop(..)
             | ExprKind::Assign(..)
@@ -1866,6 +1868,7 @@ impl Expr<'_> {
             | ExprKind::Break(..)
             | ExprKind::Continue(..)
             | ExprKind::Ret(..)
+            | ExprKind::Become(..)
             | ExprKind::Let(..)
             | ExprKind::Loop(..)
             | ExprKind::Assign(..)
@@ -2025,6 +2028,8 @@ pub enum ExprKind<'hir> {
     Continue(Destination),
     /// A `return`, with an optional value to be returned.
     Ret(Option<&'hir Expr<'hir>>),
+    /// A `become`, with the value to be returned.
+    Become(&'hir Expr<'hir>),
 
     /// Inline assembly (from `asm!`), with its outputs and inputs.
     InlineAsm(&'hir InlineAsm<'hir>),