rustc_mir: create the let and "remainder" scopes in source order.

Author: eddyb

src/librustc_mir/build/matches/mod.rs

@@ -505,14 +505,15 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             UserTypeProjections::none(),
             &mut |this, mutability, name, mode, var, span, ty, user_ty| {
                 if visibility_scope.is_none() {
-                    visibility_scope =
-                        Some(this.new_source_scope(scope_span, LintLevel::Inherited, None));
                     // If we have lints, create a new source scope
                     // that marks the lints for the locals. See the comment
                     // on the `source_info` field for why this is needed.
                     if lint_level.is_explicit() {
                         scope = this.new_source_scope(scope_span, lint_level, None);
                     }
+                visibility_scope = Some(this.new_source_scope(scope_span,
+                                                           LintLevel::Inherited,
+                                                           None));
                 }
                 let source_info = SourceInfo { span, scope };
                 let visibility_scope = visibility_scope.unwrap();

src/test/mir-opt/box_expr.rs

@@ -26,9 +26,9 @@ impl Drop for S {
 //     let mut _3: ();
 //     let mut _4: std::boxed::Box<S>;
 //     scope 1 {
+//         let _1: std::boxed::Box<S>;
 //     }
 //     scope 2 {
-//         let _1: std::boxed::Box<S>;
 //     }
 //     bb0: {
 //         StorageLive(_1);

src/test/mir-opt/issue-41110.rs

@@ -34,9 +34,9 @@ impl S {
 //    let mut _4: S;
 //    let mut _5: bool;
 //    scope 1 {
+//        let _1: ();
 //    }
 //    scope 2 {
-//        let _1: ();
 //    }
 //    ...
 //    bb0: {
@@ -48,9 +48,9 @@ impl S {
 //    let mut _5: S;
 //    let mut _6: bool;
 //    ...
-//    let mut _2: S;
-//    ...
 //    let _1: S;
 //    ...
+//    let mut _2: S;
+//    ...
 //    bb0: {
 // END rustc.test.ElaborateDrops.after.mir

src/test/mir-opt/issue-49232.rs

@@ -23,9 +23,9 @@ fn main() {
 //     let mut _5: ();
 //     let mut _6: &i32;
 //     scope 1 {
+//         let _2: i32;
 //     }
 //     scope 2 {
-//         let _2: i32;
 //     }
 //     bb0: {
 //         goto -> bb1;

src/test/mir-opt/nll/region-subtyping-basic.rs

@@ -27,10 +27,10 @@ fn main() {
 // | '_#4r    | U0 | {bb2[4..=5], bb3[0..=1]}
 // END rustc.main.nll.0.mir
 // START rustc.main.nll.0.mir
-// let _6: &'_#4r usize;
-// ...
 // let _2: &'_#3r usize;
 // ...
+// let _6: &'_#4r usize;
+// ...
 // _2 = &'_#2r _1[_3];
 // ...
 // _6 = _2;

src/test/mir-opt/packed-struct-drop-aligned.rs

@@ -24,9 +24,9 @@ impl Drop for Droppy {
 //     let mut _5: Droppy;
 //     let mut _6: Aligned;
 //     scope 1 {
+//         let mut _1: Packed;
 //     }
 //     scope 2 {
-//         let mut _1: Packed;
 //     }
 //
 //     bb0: {