Disable version_check::supports_feature on nightly

Author: oli-obk

compiler/rustc_mir_build/src/build/mod.rs

@@ -1,5 +1,6 @@
 use crate::build::expr::as_place::PlaceBuilder;
 use crate::build::scope::DropKind;
+use hir::def_id::LOCAL_CRATE;
 use itertools::Itertools;
 use rustc_apfloat::ieee::{Double, Half, Quad, Single};
 use rustc_apfloat::Float;
@@ -21,9 +22,9 @@ use rustc_middle::query::TyCtxtAt;
 use rustc_middle::thir::{self, ExprId, LintLevel, LocalVarId, Param, ParamId, PatKind, Thir};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::symbol::sym;
-use rustc_span::Span;
 use rustc_span::Symbol;
-use rustc_target::abi::FieldIdx;
+use rustc_span::{Span, DUMMY_SP};
+use rustc_target::abi::{FieldIdx, VariantIdx};
 use rustc_target::spec::abi::Abi;
 
 use super::lints;
@@ -510,6 +511,33 @@ fn construct_fn<'tcx>(
         coroutine,
     );
 
+    if tcx.sess.is_nightly_build()
+        && tcx.crate_name(LOCAL_CRATE).as_str() == "version_check"
+        && tcx.item_name(fn_def.into()).as_str() == "supports_feature"
+        && fn_sig.inputs().len() == 1
+        && let Some(ref_arg) = fn_sig.inputs()[0].builtin_deref(false)
+        && ref_arg.ty.is_str()
+        && let ty::Adt(adt, args) = return_ty.kind()
+        && tcx.lang_items().option_type() == Some(adt.did())
+        && args[0].expect_ty().is_bool()
+    {
+        let block = START_BLOCK;
+        let source_info = builder.source_info(DUMMY_SP);
+
+        builder.local_decls.push(LocalDecl::with_source_info(fn_sig.inputs()[0], source_info));
+        builder.cfg.push_assign(
+            block,
+            source_info,
+            Place::return_place(),
+            Rvalue::Aggregate(
+                Box::new(AggregateKind::Adt(adt.did(), VariantIdx::ZERO, args, None, None)),
+                Default::default(),
+            ),
+        );
+        builder.cfg.terminate(block, source_info, TerminatorKind::Return);
+        return builder.finish();
+    }
+
     let call_site_scope =
         region::Scope { id: body_id.hir_id.local_id, data: region::ScopeData::CallSite };
     let arg_scope =

tests/ui/feature-gates/version_check.rs

@@ -5,5 +5,5 @@ fn supports_feature(_: &str) -> Option<bool> {
 }
 
 fn main() {
-    assert_ne!(supports_feature("foobar"), None);
+    assert_eq!(supports_feature("foobar"), None);
 }