[gcc/devel/rust/master] lang.opt: Remove overzealous warning initialisation

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:4134055f1855ea5293fa598fc3503e07a11d1d9d

commit 4134055f1855ea5293fa598fc3503e07a11d1d9d
Author: Arthur Cohen <arthur.cohen@embecosm.com>
Date:   Wed Oct 5 10:05:26 2022 +0200

    lang.opt: Remove overzealous warning initialisation
    
    pipeline: Add default warning initialisation
    
    Option initialisations in lang.opt files are applied globally, so the
    test suites of other frontend would fail when the rust language was
    enabled.
    
    This should be reversed once @tschwinge `LangInit` option is merged

Diff:
---
 gcc/rust/lang.opt     | 6 +++---
 gcc/rust/rust-lang.cc | 7 +++++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/gcc/rust/lang.opt b/gcc/rust/lang.opt
index bb3b9983862..40297ad314d 100644
--- a/gcc/rust/lang.opt
+++ b/gcc/rust/lang.opt
@@ -39,7 +39,7 @@ Rust
 ; Documented in c.opt
 
 Wunused-variable
-Rust Var(warn_unused_variable) Init(1) Warning
+Rust Var(warn_unused_variable) Warning
 ; documented in common.opt
 
 Wunused-const-variable
@@ -47,11 +47,11 @@ Rust Warning Alias(Wunused-const-variable=, 2, 0)
 Warn when a const variable is unused.
 
 Wunused-const-variable=
-Rust Joined RejectNegative UInteger Var(warn_unused_const_variable) Init(1) Warning LangEnabledBy(Rust,Wunused-variable, 1, 0) IntegerRange(0, 2)
+Rust Joined RejectNegative UInteger Var(warn_unused_const_variable) Warning LangEnabledBy(Rust,Wunused-variable, 1, 0) IntegerRange(0, 2)
 Warn when a const variable is unused.
 
 Wunused-result
-Rust Var(warn_unused_result) Init(1) Warning
+Rust Var(warn_unused_result) Warning
 Warn if a caller of a function, marked with attribute warn_unused_result, does not use its return value.
 
 frust-crate=
diff --git a/gcc/rust/rust-lang.cc b/gcc/rust/rust-lang.cc
index c9af790f66b..72f3dc09bab 100644
--- a/gcc/rust/rust-lang.cc
+++ b/gcc/rust/rust-lang.cc
@@ -162,6 +162,13 @@ grs_langhook_init_options_struct (struct gcc_options *opts)
    * builtins */
   opts->x_flag_wrapv = 1;
 
+  /* We need to warn on unused variables by default */
+  opts->x_warn_unused_variable = 1;
+  /* For const variables too */
+  opts->x_warn_unused_const_variable = 1;
+  /* And finally unused result for #[must_use] */
+  opts->x_warn_unused_result = 1;
+
   // nothing yet - used by frontends to change specific options for the language
   Rust::Session::get_instance ().init_options ();
 }