Simplify visit_statement.

Author: cjgillot

compiler/rustc_mir_transform/src/const_prop.rs

@@ -961,13 +961,14 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
                     }
                 }
             }
-            StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => {
+            StatementKind::StorageLive(local) => {
                 let frame = self.ecx.frame_mut();
-                frame.locals[local].value = if let StatementKind::StorageLive(_) = statement.kind {
-                    LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit))
-                } else {
-                    LocalValue::Dead
-                };
+                frame.locals[local].value =
+                    LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit));
+            }
+            StatementKind::StorageDead(local) => {
+                let frame = self.ecx.frame_mut();
+                frame.locals[local].value = LocalValue::Dead;
             }
             _ => {}
         }

compiler/rustc_mir_transform/src/const_prop_lint.rs

@@ -522,75 +522,70 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
         trace!("visit_statement: {:?}", statement);
         let source_info = statement.source_info;
         self.source_info = Some(source_info);
-        if let StatementKind::Assign(box (place, ref rval)) = statement.kind {
-            let can_const_prop = self.ecx.machine.can_const_prop[place.local];
-            if let Some(()) = self.const_prop(rval, source_info, place) {
-                match can_const_prop {
-                    ConstPropMode::OnlyInsideOwnBlock => {
-                        trace!(
-                            "found local restricted to its block. \
+        match statement.kind {
+            StatementKind::Assign(box (place, ref rval)) => {
+                let can_const_prop = self.ecx.machine.can_const_prop[place.local];
+                if let Some(()) = self.const_prop(rval, source_info, place) {
+                    match can_const_prop {
+                        ConstPropMode::OnlyInsideOwnBlock => {
+                            trace!(
+                                "found local restricted to its block. \
                                 Will remove it from const-prop after block is finished. Local: {:?}",
-                            place.local
-                        );
-                    }
-                    ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
-                        trace!("can't propagate into {:?}", place);
-                        if place.local != RETURN_PLACE {
-                            Self::remove_const(&mut self.ecx, place.local);
+                                place.local
+                            );
                         }
-                    }
-                    ConstPropMode::FullConstProp => {}
-                }
-            } else {
-                // Const prop failed, so erase the destination, ensuring that whatever happens
-                // from here on, does not know about the previous value.
-                // This is important in case we have
-                // ```rust
-                // let mut x = 42;
-                // x = SOME_MUTABLE_STATIC;
-                // // x must now be uninit
-                // ```
-                // FIXME: we overzealously erase the entire local, because that's easier to
-                // implement.
-                trace!(
-                    "propagation into {:?} failed.
-                        Nuking the entire site from orbit, it's the only way to be sure",
-                    place,
-                );
-                Self::remove_const(&mut self.ecx, place.local);
-            }
-        } else {
-            match statement.kind {
-                StatementKind::SetDiscriminant { ref place, .. } => {
-                    match self.ecx.machine.can_const_prop[place.local] {
-                        ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => {
-                            if self
-                                .use_ecx(source_info, |this| this.ecx.statement(statement))
-                                .is_some()
-                            {
-                                trace!("propped discriminant into {:?}", place);
-                            } else {
+                        ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
+                            trace!("can't propagate into {:?}", place);
+                            if place.local != RETURN_PLACE {
                                 Self::remove_const(&mut self.ecx, place.local);
                             }
                         }
-                        ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
-                            Self::remove_const(&mut self.ecx, place.local);
-                        }
+                        ConstPropMode::FullConstProp => {}
                     }
+                } else {
+                    // Const prop failed, so erase the destination, ensuring that whatever happens
+                    // from here on, does not know about the previous value.
+                    // This is important in case we have
+                    // ```rust
+                    // let mut x = 42;
+                    // x = SOME_MUTABLE_STATIC;
+                    // // x must now be uninit
+                    // ```
+                    // FIXME: we overzealously erase the entire local, because that's easier to
+                    // implement.
+                    trace!(
+                        "propagation into {:?} failed.
+                        Nuking the entire site from orbit, it's the only way to be sure",
+                        place,
+                    );
+                    Self::remove_const(&mut self.ecx, place.local);
                 }
-                StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => {
-                    let frame = self.ecx.frame_mut();
-                    frame.locals[local].value =
-                        if let StatementKind::StorageLive(_) = statement.kind {
-                            LocalValue::Live(interpret::Operand::Immediate(
-                                interpret::Immediate::Uninit,
-                            ))
+            }
+            StatementKind::SetDiscriminant { ref place, .. } => {
+                match self.ecx.machine.can_const_prop[place.local] {
+                    ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => {
+                        if self.use_ecx(source_info, |this| this.ecx.statement(statement)).is_some()
+                        {
+                            trace!("propped discriminant into {:?}", place);
                         } else {
-                            LocalValue::Dead
-                        };
+                            Self::remove_const(&mut self.ecx, place.local);
+                        }
+                    }
+                    ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
+                        Self::remove_const(&mut self.ecx, place.local);
+                    }
                 }
-                _ => {}
             }
+            StatementKind::StorageLive(local) => {
+                let frame = self.ecx.frame_mut();
+                frame.locals[local].value =
+                    LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit));
+            }
+            StatementKind::StorageDead(local) => {
+                let frame = self.ecx.frame_mut();
+                frame.locals[local].value = LocalValue::Dead;
+            }
+            _ => {}
         }
 
         self.super_statement(statement, location);