Introduce enhanced_binary_op feature

compiler/rustc_feature/src/active.rs

@@ -142,6 +142,8 @@ declare_features! (
     (active, allow_internal_unstable, "1.0.0", None, None),
     /// Allows identifying the `compiler_builtins` crate.
     (active, compiler_builtins, "1.13.0", None, None),
+    /// Allows more code to compile within a binary operation context
+    (active, enhanced_binary_op, "1.60.0", None, None),
     /// Allows using the `rust-intrinsic`'s "ABI".
     (active, intrinsics, "1.0.0", None, None),
     /// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic.

compiler/rustc_mir_build/src/build/expr/into.rs

@@ -153,27 +153,51 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 //
                 // [block: If(lhs)] -true-> [else_block: dest = (rhs)]
                 //        | (false)
-                //  [shortcurcuit_block: dest = false]
+                //  [shortcircuit_block: dest = false]
                 //
                 // Or:
                 //
                 // [block: If(lhs)] -false-> [else_block: dest = (rhs)]
                 //        | (true)
-                //  [shortcurcuit_block: dest = true]
-
-                let (shortcircuit_block, mut else_block, join_block) = (
-                    this.cfg.start_new_block(),
-                    this.cfg.start_new_block(),
-                    this.cfg.start_new_block(),
-                );
-
-                let lhs = unpack!(block = this.as_local_operand(block, &this.thir[lhs]));
-                let blocks = match op {
-                    LogicalOp::And => (else_block, shortcircuit_block),
-                    LogicalOp::Or => (shortcircuit_block, else_block),
-                };
-                let term = TerminatorKind::if_(this.tcx, lhs, blocks.0, blocks.1);
-                this.cfg.terminate(block, source_info, term);
+                // [shortcircuit_block: dest = true]
+
+                let (shortcircuit_block, mut else_block, join_block) =
+                    if this.tcx.features().enhanced_binary_op {
+                        let local_scope = this.local_scope();
+
+                        let blocks = this.in_if_then_scope(local_scope, |this| {
+                            this.then_else_break(
+                                block,
+                                &this.thir[lhs],
+                                Some(local_scope),
+                                local_scope,
+                                this.thir[lhs].span,
+                            )
+                        });
+
+                        let (shortcircuit_block, else_block) = match op {
+                            LogicalOp::And => (blocks.1, blocks.0),
+                            LogicalOp::Or => (blocks.0, blocks.1),
+                        };
+
+                        (shortcircuit_block, else_block, this.cfg.start_new_block())
+                    } else {
+                        let (shortcircuit_block, else_block, join_block) = (
+                            this.cfg.start_new_block(),
+                            this.cfg.start_new_block(),
+                            this.cfg.start_new_block(),
+                        );
+
+                        let lhs = unpack!(block = this.as_local_operand(block, &this.thir[lhs]));
+                        let blocks = match op {
+                            LogicalOp::And => (else_block, shortcircuit_block),
+                            LogicalOp::Or => (shortcircuit_block, else_block),
+                        };
+                        let term = TerminatorKind::if_(this.tcx, lhs, blocks.0, blocks.1);
+                        this.cfg.terminate(block, source_info, term);
+
+                        (shortcircuit_block, else_block, join_block)
+                    };
 
                 this.cfg.push_assign_constant(
                     shortcircuit_block,
@@ -188,12 +212,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         },
                     },
                 );
-                this.cfg.goto(shortcircuit_block, source_info, join_block);
 
                 let rhs = unpack!(else_block = this.as_local_operand(else_block, &this.thir[rhs]));
                 this.cfg.push_assign(else_block, source_info, destination, Rvalue::Use(rhs));
+                this.cfg.goto(shortcircuit_block, source_info, join_block);
                 this.cfg.goto(else_block, source_info, join_block);
-
                 join_block.unit()
             }
             ExprKind::Loop { body } => {

compiler/rustc_span/src/symbol.rs

@@ -611,6 +611,7 @@ symbols! {
         enclosing_scope,
         encode,
         end,
+        enhanced_binary_op,
         env,
         env_macro,
         eprint_macro,

src/test/ui/rfc-2497-if-let-chains/feature-gate-enhanced_binary_op.rs

@@ -0,0 +1,20 @@
+#![feature(enhanced_binary_op)]
+
+fn and_chain() {
+    let z;
+    if true && { z = 3; true } && z == 3 {}
+}
+
+fn and_chain_2() {
+    let z;
+    true && { z = 3; true } && z == 3;
+}
+
+fn or_chain() {
+    let z;
+    if false || { z = 3; false } || z == 3 {}
+    //~^ ERROR use of possibly-uninitialized
+}
+
+fn main() {
+}

src/test/ui/rfc-2497-if-let-chains/feature-gate-enhanced_binary_op.stderr

@@ -0,0 +1,9 @@
+error[E0381]: use of possibly-uninitialized variable: `z`
+  --> $DIR/feature-gate-enhanced_binary_op.rs:15:37
+   |
+LL |     if false || { z = 3; false } || z == 3 {}
+   |                                     ^ use of possibly-uninitialized `z`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0381`.