Add stable_bare_rustc helper in run-make-support

src/tools/run-make-support/src/external_deps/rustc.rs

@@ -22,6 +22,15 @@ pub fn bare_rustc() -> Rustc {
     Rustc::bare()
 }
 
+/// Construct a plain `rustc` invocation with no flags set that behaves like a stable compiler,
+/// i.e. rejects unstable flags.
+/// Note that [`set_host_compiler_dylib_path`] still presets the environment variable
+/// `HOST_RUSTC_DYLIB_PATH` by default.
+#[track_caller]
+pub fn stable_bare_rustc() -> Rustc {
+    Rustc::bare_stable()
+}
+
 /// Construct a `rustc` invocation for building `minicore`.
 ///
 /// This function:
@@ -76,9 +85,6 @@ pub fn rustc_path() -> String {
 fn setup_common() -> Command {
     let mut cmd = Command::new(rustc_path());
     set_host_compiler_dylib_path(&mut cmd);
-    if let Ok(codegen_backend) = std::env::var("RUSTC_CODEGEN_BACKEND") {
-        cmd.arg(format!("-Zcodegen-backend={codegen_backend}"));
-    }
     cmd
 }
 
@@ -100,6 +106,10 @@ impl Rustc {
             cmd.arg("-Ctarget-feature=-crt-static");
         }
 
+        if let Ok(codegen_backend) = std::env::var("RUSTC_CODEGEN_BACKEND") {
+            cmd.arg(format!("-Zcodegen-backend={codegen_backend}"));
+        }
+
         // Automatically default to cross-compilation
         Self { cmd, target: Some(target()) }
     }
@@ -111,6 +121,14 @@ impl Rustc {
         Self { cmd, target: None }
     }
 
+    /// Construct a bare `rustc` invocation with no flags set that acts like a stable compiler.
+    #[track_caller]
+    pub fn bare_stable() -> Self {
+        let mut cmd = setup_common();
+        cmd.env("RUSTC_BOOTSTRAP", "-1");
+        Self { cmd, target: None }
+    }
+
     // Argument provider methods
 
     /// Configure the compilation environment.

src/tools/run-make-support/src/lib.rs

@@ -79,7 +79,9 @@ pub use crate::external_deps::llvm::{
     llvm_readobj,
 };
 pub use crate::external_deps::python::python_command;
-pub use crate::external_deps::rustc::{self, Rustc, bare_rustc, rustc, rustc_minicore, rustc_path};
+pub use crate::external_deps::rustc::{
+    self, Rustc, bare_rustc, rustc, rustc_minicore, rustc_path, stable_bare_rustc,
+};
 pub use crate::external_deps::rustdoc::{Rustdoc, bare_rustdoc, rustdoc};
 // Path-related helpers.
 pub use crate::path_helpers::{

tests/run-make/const-destruct-stable-toolchain/rmake.rs

@@ -1,17 +1,15 @@
 //@ needs-target-std
-// FIXME: Once GCC backend is fixed, remove this `ignore-backends`.
 //@ ignore-backends: gcc
 
 // Test that the suggestion to constrain a type parameter that is dropped in a const
 // function with a `[const] Destruct` bound is only offered on nightly, since the bound
 // requires an unstable feature.
 
-use run_make_support::{diff, rustc};
+use run_make_support::{diff, rustc, stable_bare_rustc};
 
 fn main() {
-    let out = rustc()
+    let out = stable_bare_rustc()
         .input("const-drop.rs")
-        .env("RUSTC_BOOTSTRAP", "-1")
         .run_fail()
         .assert_stderr_not_contains("consider restricting type parameter `T`")
         .stderr_utf8();

tests/run-make/const-trait-stable-toolchain/rmake.rs

@@ -1,16 +1,14 @@
 //@ needs-target-std
-// FIXME: Once GCC backend is fixed, remove this `ignore-backends`.
 //@ ignore-backends: gcc
 
 // Test output of const super trait errors in both stable and nightly.
 // We don't want to provide suggestions on stable that only make sense in nightly.
 
-use run_make_support::{diff, rustc};
+use run_make_support::{diff, rustc, stable_bare_rustc};
 
 fn main() {
-    let out = rustc()
+    let out = stable_bare_rustc()
         .input("const-super-trait.rs")
-        .env("RUSTC_BOOTSTRAP", "-1")
         .cfg("feature_enabled")
         .run_fail()
         .assert_stderr_not_contains("as `const` to allow it to have `const` implementations")
@@ -35,9 +33,8 @@ fn main() {
         .expected_file("const-super-trait-nightly-enabled.stderr")
         .actual_text("(rustc)", &out)
         .run();
-    let out = rustc()
+    let out = stable_bare_rustc()
         .input("const-super-trait.rs")
-        .env("RUSTC_BOOTSTRAP", "-1")
         .run_fail()
         .assert_stderr_not_contains("enable `#![feature(const_trait_impl)]` in your crate and mark")
         .assert_stderr_not_contains("as `const` to allow it to have `const` implementations")

tests/run-make/issue-149402-suggest-unresolve/rmake.rs

@@ -4,18 +4,12 @@
 //!
 //@ only-nightly
 //@ needs-target-std
-// FIXME: Once GCC backend is fixed, remove this `ignore-backends`.
 //@ ignore-backends: gcc
 
-use run_make_support::{diff, rustc, similar};
+use run_make_support::{diff, rustc, similar, stable_bare_rustc};
 
 fn main() {
-    let stable_like = rustc()
-        .env("RUSTC_BOOTSTRAP", "-1")
-        .edition("2024")
-        .input("foo.rs")
-        .run_fail()
-        .stderr_utf8();
+    let stable_like = stable_bare_rustc().edition("2024").input("foo.rs").run_fail().stderr_utf8();
 
     assert!(!stable_like.contains("CoroutineState::Complete"));
     diff().expected_file("stable.err").actual_text("stable_like", &stable_like).run();

tests/run-make/missing-unstable-trait-bound/rmake.rs

@@ -2,17 +2,15 @@
 //@ ignore-wasm32
 //@ ignore-wasm64
 // ignore-tidy-linelength
-// FIXME: Once GCC backend is fixed, remove this `ignore-backends`.
 //@ ignore-backends: gcc
 
 // Ensure that on stable we don't suggest restricting with an unsafe trait and we continue
 // mentioning the rest of the obligation chain.
 
-use run_make_support::{diff, rustc};
+use run_make_support::{diff, stable_bare_rustc};
 
 fn main() {
-    let out = rustc()
-        .env("RUSTC_BOOTSTRAP", "-1")
+    let out = stable_bare_rustc()
         .input("missing-bound.rs")
         .run_fail()
         .assert_stderr_not_contains("help: consider restricting type parameter `T`")

tests/run-make/print-request-help-stable-unstable/rmake.rs

@@ -2,18 +2,13 @@
 //!
 //! Issue: <https://github.com/rust-lang/rust/issues/138698>
 
-// FIXME: Once GCC backend is fixed, remove this `ignore-backends`.
 //@ ignore-backends: gcc
 
-use run_make_support::{diff, rustc, similar};
+use run_make_support::{diff, rustc, similar, stable_bare_rustc};
 
 fn main() {
-    let stable_invalid_print_request_help = rustc()
-        .env("RUSTC_BOOTSTRAP", "-1")
-        .cfg("force_stable")
-        .print("xxx")
-        .run_fail()
-        .stderr_utf8();
+    let stable_invalid_print_request_help =
+        stable_bare_rustc().print("xxx").run_fail().stderr_utf8();
     assert!(!stable_invalid_print_request_help.contains("all-target-specs-json"));
     diff()
         .expected_file("stable-invalid-print-request-help.err")