1 files changed, 20 insertions, 0 deletions
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index c9b5c659f0f..837c069b599 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -27,6 +27,7 @@ use rustc_middle::middle::resolve_bound_vars::Set1;
 use rustc_middle::{bug, span_bug};
 use rustc_session::config::{CrateType, ResolveDocLinks};
 use rustc_session::lint;
+use rustc_session::parse::feature_err;
 use rustc_span::source_map::{respan, Spanned};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, Span, SyntaxContext};
@@ -4138,6 +4139,25 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                     && PrimTy::from_name(path[0].ident.name).is_some() =>
             {
                 let prim = PrimTy::from_name(path[0].ident.name).unwrap();
+                let tcx = self.r.tcx();
+
+                let gate_err_sym_msg = match prim {
+                    PrimTy::Float(FloatTy::F16) if !tcx.features().f16 => {
+                        Some((sym::f16, "the type `f16` is unstable"))
+                    }
+                    PrimTy::Float(FloatTy::F128) if !tcx.features().f128 => {
+                        Some((sym::f128, "the type `f128` is unstable"))
+                    }
+                    _ => None,
+                };
+
+                if let Some((sym, msg)) = gate_err_sym_msg {
+                    let span = path[0].ident.span;
+                    if !span.allows_unstable(sym) {
+                        feature_err(tcx.sess, sym, span, msg).emit();
+                    }
+                };
+
                 PartialRes::with_unresolved_segments(Res::PrimTy(prim), path.len() - 1)
             }
             PathResult::Module(ModuleOrUniformRoot::Module(module)) => {