From 18df72142ae7694c5661f0feb7d78ffc7b433e6b Mon Sep 17 00:00:00 2001
From: Matthew Jasper <mjjasper1@gmail.com>
Date: Tue, 24 Dec 2019 14:31:03 +0000
Subject: [PATCH] Remove `-Znll-dont-emit-read-for-match`

---
 src/librustc/ty/context.rs            | 13 -------------
 src/librustc_mir/build/matches/mod.rs |  8 +-------
 src/librustc_session/options.rs       |  2 --
 3 files changed, 1 insertion(+), 22 deletions(-)

diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 39341de6367f..e99e00a366d3 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -1370,19 +1370,6 @@ impl<'tcx> TyCtxt<'tcx> {
         self.borrowck_mode().migrate()
     }
 
-    /// If `true`, make MIR codegen for `match` emit a temp that holds a
-    /// borrow of the input to the match expression.
-    pub fn generate_borrow_of_any_match_input(&self) -> bool {
-        self.emit_read_for_match()
-    }
-
-    /// If `true`, make MIR codegen for `match` emit FakeRead
-    /// statements (which simulate the maximal effect of executing the
-    /// patterns in a match arm).
-    pub fn emit_read_for_match(&self) -> bool {
-        !self.sess.opts.debugging_opts.nll_dont_emit_read_for_match
-    }
-
     /// What mode(s) of borrowck should we run? AST? MIR? both?
     /// (Also considers the `#![feature(nll)]` setting.)
     pub fn borrowck_mode(&self) -> BorrowckMode {
diff --git a/src/librustc_mir/build/matches/mod.rs b/src/librustc_mir/build/matches/mod.rs
index e1a51e2fb35e..60049a3a9fe4 100644
--- a/src/librustc_mir/build/matches/mod.rs
+++ b/src/librustc_mir/build/matches/mod.rs
@@ -108,8 +108,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         scrutinee: ExprRef<'tcx>,
         arms: Vec<Arm<'tcx>>,
     ) -> BlockAnd<()> {
-        let tcx = self.hir.tcx();
-
         // Step 1. Evaluate the scrutinee and add the fake read of it.
 
         let scrutinee_span = scrutinee.span();
@@ -183,11 +181,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         // The set of places that we are creating fake borrows of. If there are
         // no match guards then we don't need any fake borrows, so don't track
         // them.
-        let mut fake_borrows = if match_has_guard && tcx.generate_borrow_of_any_match_input() {
-            Some(FxHashSet::default())
-        } else {
-            None
-        };
+        let mut fake_borrows = if match_has_guard { Some(FxHashSet::default()) } else { None };
 
         // These candidates are kept sorted such that the highest priority
         // candidate comes first in the list. (i.e., same order as in source)
diff --git a/src/librustc_session/options.rs b/src/librustc_session/options.rs
index c90213f09582..38c17bbbde79 100644
--- a/src/librustc_session/options.rs
+++ b/src/librustc_session/options.rs
@@ -872,8 +872,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "choose which RELRO level to use"),
     nll_facts: bool = (false, parse_bool, [UNTRACKED],
                        "dump facts from NLL analysis into side files"),
-    nll_dont_emit_read_for_match: bool = (false, parse_bool, [UNTRACKED],
-        "in match codegen, do not include FakeRead statements (used by mir-borrowck)"),
     dont_buffer_diagnostics: bool = (false, parse_bool, [UNTRACKED],
         "emit diagnostics rather than buffering (breaks NLL error downgrading, sorting)."),
     polonius: bool = (false, parse_bool, [UNTRACKED],