Recurse into statement before applying its effect.

Author: cjgillot

compiler/rustc_mir_transform/src/const_prop.rs

@@ -829,6 +829,10 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
 
     fn visit_statement(&mut self, statement: &mut Statement<'tcx>, location: Location) {
         trace!("visit_statement: {:?}", statement);
+
+        // Recurse into statement before applying the assignment.
+        self.super_statement(statement, location);
+
         match statement.kind {
             StatementKind::Assign(box (place, ref mut rval)) => {
                 let can_const_prop = self.ecx.machine.can_const_prop[place.local];
@@ -905,8 +909,6 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
             }
             _ => {}
         }
-
-        self.super_statement(statement, location);
     }
 
     fn visit_terminator(&mut self, terminator: &mut Terminator<'tcx>, location: Location) {

compiler/rustc_mir_transform/src/const_prop_lint.rs

@@ -511,6 +511,10 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
         trace!("visit_statement: {:?}", statement);
         let source_info = statement.source_info;
         self.source_info = Some(source_info);
+
+        // Recurse into statement before applying the assignment.
+        self.super_statement(statement, location);
+
         match statement.kind {
             StatementKind::Assign(box (place, ref rval)) => {
                 let can_const_prop = self.ecx.machine.can_const_prop[place.local];
@@ -576,8 +580,6 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
             }
             _ => {}
         }
-
-        self.super_statement(statement, location);
     }
 
     fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {

tests/ui/consts/const-err-late.stderr

@@ -10,12 +10,6 @@ note: erroneous constant used
 LL |     black_box((S::<i32>::FOO, S::<u32>::FOO));
    |                ^^^^^^^^^^^^^
 
-note: erroneous constant used
-  --> $DIR/const-err-late.rs:19:16
-   |
-LL |     black_box((S::<i32>::FOO, S::<u32>::FOO));
-   |                ^^^^^^^^^^^^^
-
 error[E0080]: evaluation of `S::<u32>::FOO` failed
   --> $DIR/const-err-late.rs:13:21
    |
@@ -34,6 +28,12 @@ note: erroneous constant used
 LL |     black_box((S::<i32>::FOO, S::<u32>::FOO));
    |                ^^^^^^^^^^^^^
 
+note: erroneous constant used
+  --> $DIR/const-err-late.rs:19:16
+   |
+LL |     black_box((S::<i32>::FOO, S::<u32>::FOO));
+   |                ^^^^^^^^^^^^^
+
 error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0080`.