Rollup merge of rust-lang#126981 - Zalathar:enums, r=Nadrieril

Replace some magic booleans in match-lowering with enums

This PR takes some boolean arguments used by the match-lowering code, and replaces them with dedicated enums that more clearly express their effect, while also making it much easier to find how each value is ultimately used.

Author: matthiaskrgr

compiler/rustc_mir_build/src/build/block.rs

@@ -1,3 +1,4 @@
+use crate::build::matches::{DeclareLetBindings, EmitStorageLive, ScheduleDrops};
 use crate::build::ForGuard::OutsideGuard;
 use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
 use rustc_middle::middle::region::Scope;
@@ -201,7 +202,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             pattern,
                             UserTypeProjections::none(),
                             &mut |this, _, _, node, span, _, _| {
-                                this.storage_live_binding(block, node, span, OutsideGuard, true);
+                                this.storage_live_binding(
+                                    block,
+                                    node,
+                                    span,
+                                    OutsideGuard,
+                                    ScheduleDrops::Yes,
+                                );
                             },
                         );
                         let else_block_span = this.thir[*else_block].span;
@@ -213,8 +220,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                                     pattern,
                                     None,
                                     initializer_span,
-                                    false,
-                                    true,
+                                    DeclareLetBindings::No,
+                                    EmitStorageLive::No,
                                 )
                             });
                         matching.and(failure)
@@ -291,7 +298,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             pattern,
                             UserTypeProjections::none(),
                             &mut |this, _, _, node, span, _, _| {
-                                this.storage_live_binding(block, node, span, OutsideGuard, true);
+                                this.storage_live_binding(
+                                    block,
+                                    node,
+                                    span,
+                                    OutsideGuard,
+                                    ScheduleDrops::Yes,
+                                );
                                 this.schedule_drop_for_binding(node, span, OutsideGuard);
                             },
                         )

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

@@ -1,6 +1,7 @@
 //! See docs in build/expr/mod.rs
 
 use crate::build::expr::category::{Category, RvalueFunc};
+use crate::build::matches::DeclareLetBindings;
 use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder, NeedsTemporary};
 use rustc_ast::InlineAsmOptions;
 use rustc_data_structures::fx::FxHashMap;
@@ -86,7 +87,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                                     cond,
                                     Some(condition_scope), // Temp scope
                                     source_info,
-                                    true, // Declare `let` bindings normally
+                                    DeclareLetBindings::Yes, // Declare `let` bindings normally
                                 ));
 
                                 // Lower the `then` arm into its block.
@@ -163,7 +164,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             source_info,
                             // This flag controls how inner `let` expressions are lowered,
                             // but either way there shouldn't be any of those in here.
-                            true,
+                            DeclareLetBindings::LetNotPermitted,
                         )
                     });
                 let (short_circuit, continuation, constant) = match op {