do not complain about unstable target features on nightly

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -383,8 +383,10 @@ pub fn internal_target_features<'a, const N: usize>(
                         } else {
                             sess.dcx().emit_warn(diag);
                         }
-                    } else if stability.requires_nightly(/* in_cfg */ false).is_some() {
-                        // An unstable feature. Warn about using it. It makes little sense
+                    } else if stability.requires_nightly(/* in_cfg */ false).is_some()
+                        && !sess.is_nightly_build()
+                    {
+                        // An unstable feature. Warn about using it on stable. It makes little sense
                         // to hard-error here since we just warn about fully unknown
                         // features above.
                         let note = if stability.is_cfg_stable_toggle_unstable() {

compiler/rustc_session/src/session.rs

@@ -427,6 +427,10 @@ impl EarlySession {
     pub fn merge_functions(&self) -> MergeFunctions {
         self.opts.unstable_opts.merge_functions.unwrap_or(self.target.merge_functions)
     }
+
+    pub fn is_nightly_build(&self) -> bool {
+        self.opts.unstable_features.is_nightly_build()
+    }
 }
 
 /// Some info about the backend, returned by `CodegenBackend::init` and put into the `Session`.

src/doc/rustc-dev-guide/src/tests/misc.md

@@ -12,15 +12,10 @@ This is a bootstrap/compiler implementation detail, but it can also be useful fo
   This is useful because some behaviors of the compiler (e.g. diagnostics)
   can differ depending on whether the compiler is nightly or not.
 
-In `ui` tests and other test suites that support `//@ rustc-env`, you can specify
-
-```rust,ignore
-// Force unstable features to be usable on stable rustc
-//@ rustc-env:RUSTC_BOOTSTRAP=1
-
-// Or force nightly rustc to pretend it is a stable rustc
-//@ rustc-env:RUSTC_BOOTSTRAP=-1
-```
+Note that setting `RUSTC_BOOTSTRAP` in ui tests (e.g. via `//@ rustc-env`) is pointless since ui
+tests inherit the bootstrap env var from bootstrap (so it's set to `1` by default), and since
+compiletest itself passes `-Z` flags (so `-1` breaks the test). To test stable-only behavior, you
+need to write a `run-make` test instead.
 
 For `run-make`/`run-make-cargo` tests, `//@ rustc-env` is not supported.
 You can do something like the following for individual `rustc` invocations.

tests/run-make/unstable-target-feature/rmake.rs

@@ -0,0 +1,20 @@
+//@ only-x86_64
+// 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};
+
+fn main() {
+    let out = rustc()
+        .env("RUSTC_BOOTSTRAP", "-1")
+        .input("unstable-target-feature.rs")
+        .args(&["-Ctarget-feature=+x87", "--crate-type=rlib"])
+        .run()
+        .assert_stderr_not_contains("help: consider restricting type parameter `T`")
+        .assert_stderr_contains("unstable feature")
+        .stderr_utf8();
+    diff().expected_file("unstable-target-feature.stderr").actual_text("(stable rustc)", &out).run()
+}

tests/run-make/unstable-target-feature/unstable-target-feature.rs

@@ -0,0 +1,2 @@
+/// Tidy is unhappy if we leave the file empty.
+pub fn empty() {}

tests/run-make/unstable-target-feature/unstable-target-feature.stderr

@@ -0,0 +1,8 @@
+warning: unstable feature specified for `-Ctarget-feature`: `x87`
+  |
+  = note: this feature is not stably supported; its behavior can change in the future
+  = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+  = note: for more information, see issue #162235 <https://github.com/rust-lang/rust/issues/162235>
+
+warning: 1 warning emitted
+

tests/ui/abi/riscv-discoverability-guidance.riscv32.stderr

@@ -1,11 +1,5 @@
-warning: unstable feature specified for `-Ctarget-feature`: `unaligned-scalar-mem`
-   |
-   = note: this feature is not stably supported; its behavior can change in the future
-   = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #162235 <https://github.com/rust-lang/rust/issues/162235>
-
 error[E0703]: invalid ABI: found `riscv-interrupt`
-  --> $DIR/riscv-discoverability-guidance.rs:21:8
+  --> $DIR/riscv-discoverability-guidance.rs:16:8
    |
 LL | extern "riscv-interrupt" fn isr() {}
    |        ^^^^^^^^^^^^^^^^^ invalid ABI
@@ -17,7 +11,7 @@ LL | extern "riscv-interrupt-m" fn isr() {}
    |                        ++
 
 error[E0703]: invalid ABI: found `riscv-interrupt-u`
-  --> $DIR/riscv-discoverability-guidance.rs:26:8
+  --> $DIR/riscv-discoverability-guidance.rs:21:8
    |
 LL | extern "riscv-interrupt-u" fn isr_U() {}
    |        ^^^^^^^^^^^^^^^^^^^ invalid ABI
@@ -29,6 +23,6 @@ LL - extern "riscv-interrupt-u" fn isr_U() {}
 LL + extern "riscv-interrupt-m" fn isr_U() {}
    |
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0703`.

tests/ui/abi/riscv-discoverability-guidance.riscv64.stderr

@@ -1,11 +1,5 @@
-warning: unstable feature specified for `-Ctarget-feature`: `unaligned-scalar-mem`
-   |
-   = note: this feature is not stably supported; its behavior can change in the future
-   = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #162235 <https://github.com/rust-lang/rust/issues/162235>
-
 error[E0703]: invalid ABI: found `riscv-interrupt`
-  --> $DIR/riscv-discoverability-guidance.rs:21:8
+  --> $DIR/riscv-discoverability-guidance.rs:16:8
    |
 LL | extern "riscv-interrupt" fn isr() {}
    |        ^^^^^^^^^^^^^^^^^ invalid ABI
@@ -17,7 +11,7 @@ LL | extern "riscv-interrupt-m" fn isr() {}
    |                        ++
 
 error[E0703]: invalid ABI: found `riscv-interrupt-u`
-  --> $DIR/riscv-discoverability-guidance.rs:26:8
+  --> $DIR/riscv-discoverability-guidance.rs:21:8
    |
 LL | extern "riscv-interrupt-u" fn isr_U() {}
    |        ^^^^^^^^^^^^^^^^^^^ invalid ABI
@@ -29,6 +23,6 @@ LL - extern "riscv-interrupt-u" fn isr_U() {}
 LL + extern "riscv-interrupt-m" fn isr_U() {}
    |
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0703`.

tests/ui/abi/riscv-discoverability-guidance.rs

@@ -10,11 +10,6 @@
 #![no_core]
 #![feature(no_core, lang_items, abi_riscv_interrupt)]
 
-//~? WARN unstable feature specified for `-Ctarget-feature`
-//~? NOTE this feature is not stably supported; its behavior can change in the future
-//~? NOTE previously accepted
-//~? NOTE for more information, see issue
-
 extern crate minicore;
 use minicore::*;
 

tests/ui/abi/sparcv8plus.rs

@@ -12,7 +12,6 @@
 //@[sparc_cpu_v9_feature_v8plus] needs-llvm-components: sparc
 //@ ignore-backends: gcc
 
-//[sparc_feature_v8plus,sparc_cpu_v9_feature_v8plus]~? WARN unstable feature specified for `-Ctarget-feature`
 //[sparc_feature_v8plus,sparc_cpu_v9_feature_v8plus]~? WARN `v8plus` must be disabled
 
 #![crate_type = "rlib"]

tests/ui/abi/sparcv8plus.sparc.stderr

@@ -1,5 +1,5 @@
 error: -v8plus,-v9
-  --> $DIR/sparcv8plus.rs:31:1
+  --> $DIR/sparcv8plus.rs:30:1
    |
 LL | compile_error!("-v8plus,-v9");
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/abi/sparcv8plus.sparc_cpu_v9.stderr

@@ -1,5 +1,5 @@
 error: -v8plus,+v9
-  --> $DIR/sparcv8plus.rs:44:1
+  --> $DIR/sparcv8plus.rs:43:1
    |
 LL | compile_error!("-v8plus,+v9");
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/abi/sparcv8plus.sparc_cpu_v9_feature_v8plus.stderr

@@ -1,19 +1,13 @@
-warning: unstable feature specified for `-Ctarget-feature`: `v8plus`
-   |
-   = note: this feature is not stably supported; its behavior can change in the future
-   = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #162235 <https://github.com/rust-lang/rust/issues/162235>
-
 warning: target feature `v8plus` must be disabled to ensure that the ABI of the current target can be implemented correctly
    |
    = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #162235 <https://github.com/rust-lang/rust/issues/162235>
 
 error: +v8plus,+v9
-  --> $DIR/sparcv8plus.rs:35:1
+  --> $DIR/sparcv8plus.rs:34:1
    |
 LL | compile_error!("+v8plus,+v9");
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error; 2 warnings emitted
+error: aborting due to 1 previous error; 1 warning emitted
 

tests/ui/abi/sparcv8plus.sparc_feature_v8plus.stderr

@@ -1,19 +1,13 @@
-warning: unstable feature specified for `-Ctarget-feature`: `v8plus`
-   |
-   = note: this feature is not stably supported; its behavior can change in the future
-   = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #162235 <https://github.com/rust-lang/rust/issues/162235>
-
 warning: target feature `v8plus` must be disabled to ensure that the ABI of the current target can be implemented correctly
    |
    = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #162235 <https://github.com/rust-lang/rust/issues/162235>
 
 error: +v8plus,-v9 (FIXME)
-  --> $DIR/sparcv8plus.rs:40:1
+  --> $DIR/sparcv8plus.rs:39:1
    |
 LL | compile_error!("+v8plus,-v9 (FIXME)");
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error; 2 warnings emitted
+error: aborting due to 1 previous error; 1 warning emitted
 

tests/ui/abi/sparcv8plus.sparcv8plus.stderr

@@ -1,5 +1,5 @@
 error: +v8plus,+v9
-  --> $DIR/sparcv8plus.rs:35:1
+  --> $DIR/sparcv8plus.rs:34:1
    |
 LL | compile_error!("+v8plus,+v9");
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/asm/hexagon-register-pairs.rs

@@ -7,8 +7,6 @@
 #![crate_type = "lib"]
 #![no_core]
 
-//~? WARN unstable feature specified for `-Ctarget-feature`: `hvx-length128b`
-
 extern crate minicore;
 use minicore::*;
 

tests/ui/asm/hexagon-register-pairs.stderr

@@ -1,11 +1,5 @@
-warning: unstable feature specified for `-Ctarget-feature`: `hvx-length128b`
-   |
-   = note: this feature is not stably supported; its behavior can change in the future
-   = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #162235 <https://github.com/rust-lang/rust/issues/162235>
-
 error: avoid using named labels in inline assembly
-  --> $DIR/hexagon-register-pairs.rs:32:15
+  --> $DIR/hexagon-register-pairs.rs:30:15
    |
 LL |         asm!("label1: r7:6 = combine(#2, #3)");
    |               ^^^^^^
@@ -15,13 +9,13 @@ LL |         asm!("label1: r7:6 = combine(#2, #3)");
    = note: `#[deny(named_asm_labels)]` on by default
 
 error: avoid using named labels in inline assembly
-  --> $DIR/hexagon-register-pairs.rs:35:15
+  --> $DIR/hexagon-register-pairs.rs:33:15
    |
 LL |         asm!("hexagon_label: nop");
    |               ^^^^^^^^^^^^^
    |
    = help: only local labels of the form `<number>:` should be used in inline asm
    = note: see the asm section of Rust By Example <https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels> for more information
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 

tests/ui/asm/hexagon/bad-reg.rs

@@ -3,8 +3,6 @@
 //@ needs-llvm-components: hexagon
 //@ ignore-backends: gcc
 
-//~? WARN unstable feature specified for `-Ctarget-feature`: `hvx-length128b`
-
 #![crate_type = "lib"]
 #![feature(no_core, asm_experimental_arch)]
 #![no_core]