Reintroduce hir::ExprKind::If

4 files changed, 38 insertions, 4 deletions

diff --git a/compiler/rustc_passes/src/check_const.rs b/compiler/rustc_passes/src/check_const.rs
index 2d6bbff460d..c887a860303 100644
--- a/compiler/rustc_passes/src/check_const.rs
+++ b/compiler/rustc_passes/src/check_const.rs
@@ -49,9 +49,7 @@ impl NonConstExpr {
 
             // All other expressions are allowed.
             Self::Loop(Loop | While | WhileLet)
-            | Self::Match(
-                WhileDesugar | WhileLetDesugar | Normal | IfDesugar { .. } | IfLetDesugar { .. },
-            ) => &[],
+            | Self::Match(WhileDesugar | WhileLetDesugar | Normal | IfLetDesugar { .. }) => &[],
         };
 
         Some(gates)
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index fcea1b29ec3..6202cc312fc 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -419,7 +419,7 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
             }
 
             // live nodes required for interesting control flow:
-            hir::ExprKind::Match(..) | hir::ExprKind::Loop(..) => {
+            hir::ExprKind::If(..) | hir::ExprKind::Match(..) | hir::ExprKind::Loop(..) => {
                 self.add_live_node_for_node(expr.hir_id, ExprNode(expr.span));
                 intravisit::walk_expr(self, expr);
             }
@@ -846,6 +846,29 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
             // at the label ident
             hir::ExprKind::Loop(ref blk, _, _) => self.propagate_through_loop(expr, &blk, succ),
 
+            hir::ExprKind::If(ref cond, ref then, ref else_opt) => {
+                //
+                //     (cond)
+                //       |
+                //       v
+                //     (expr)
+                //     /   \
+                //    |     |
+                //    v     v
+                //  (then)(els)
+                //    |     |
+                //    v     v
+                //   (  succ  )
+                //
+                let else_ln =
+                    self.propagate_through_opt_expr(else_opt.as_ref().map(|e| &**e), succ);
+                let then_ln = self.propagate_through_expr(&then, succ);
+                let ln = self.live_node(expr.hir_id, expr.span);
+                self.init_from_succ(ln, else_ln);
+                self.merge_from_succ(ln, then_ln);
+                self.propagate_through_expr(&cond, ln)
+            }
+
             hir::ExprKind::Match(ref e, arms, _) => {
                 //
                 //      (e)
@@ -1336,6 +1359,7 @@ fn check_expr<'tcx>(this: &mut Liveness<'_, 'tcx>, expr: &'tcx Expr<'tcx>) {
         | hir::ExprKind::Tup(..)
         | hir::ExprKind::Binary(..)
         | hir::ExprKind::Cast(..)
+        | hir::ExprKind::If(..)
         | hir::ExprKind::DropTemps(..)
         | hir::ExprKind::Unary(..)
         | hir::ExprKind::Ret(..)
diff --git a/compiler/rustc_passes/src/naked_functions.rs b/compiler/rustc_passes/src/naked_functions.rs
index 788f1df328c..93fb23c018b 100644
--- a/compiler/rustc_passes/src/naked_functions.rs
+++ b/compiler/rustc_passes/src/naked_functions.rs
@@ -201,6 +201,7 @@ impl<'tcx> CheckInlineAssembly<'tcx> {
             | ExprKind::Type(..)
             | ExprKind::Loop(..)
             | ExprKind::Match(..)
+            | ExprKind::If(..)
             | ExprKind::Closure(..)
             | ExprKind::Assign(..)
             | ExprKind::AssignOp(..)
diff --git a/compiler/rustc_passes/src/region.rs b/compiler/rustc_passes/src/region.rs
index 1af79abe4b9..91421d7f5f2 100644
--- a/compiler/rustc_passes/src/region.rs
+++ b/compiler/rustc_passes/src/region.rs
@@ -241,6 +241,17 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
                 terminating(r.hir_id.local_id);
             }
 
+            hir::ExprKind::If(ref expr, ref then, Some(ref otherwise)) => {
+                terminating(expr.hir_id.local_id);
+                terminating(then.hir_id.local_id);
+                terminating(otherwise.hir_id.local_id);
+            }
+
+            hir::ExprKind::If(ref expr, ref then, None) => {
+                terminating(expr.hir_id.local_id);
+                terminating(then.hir_id.local_id);
+            }
+
             hir::ExprKind::Loop(ref body, _, _) => {
                 terminating(body.hir_id.local_id);
             }