Don't auto-inline const fn

Author: oli-obk

src/librustc/ty/instance.rs

@@ -173,10 +173,7 @@ impl<'tcx> InstanceDef<'tcx> {
             // available to normal end-users.
             return true
         }
-        let codegen_fn_attrs = tcx.codegen_fn_attrs(self.def_id());
-        // need to use `is_const_fn_raw` since we don't really care if the user can use it as a
-        // const fn, just whether the function should be inlined
-        codegen_fn_attrs.requests_inline() || tcx.is_const_fn_raw(self.def_id())
+        tcx.codegen_fn_attrs(self.def_id()).requests_inline()
     }
 }
 

src/test/codegen-units/item-collection/unreferenced-const-fn.rs

@@ -11,11 +11,10 @@
 // ignore-tidy-linelength
 // compile-flags:-Zprint-mono-items=lazy
 
-// NB: We do not expect *any* monomorphization to be generated here.
-
 #![deny(dead_code)]
 #![crate_type = "rlib"]
 
+//~ MONO_ITEM fn unreferenced_const_fn::foo[0] @@ unreferenced_const_fn-cgu.0[External]
 pub const fn foo(x: u32) -> u32 {
     x + 0xf00
 }

src/test/ui/consts/auxiliary/const_fn_lib.rs

@@ -10,6 +10,24 @@
 
 // Crate that exports a const fn. Used for testing cross-crate.
 
+#![feature(const_fn)]
 #![crate_type="rlib"]
 
-pub const fn foo() -> usize { 22 } //~ ERROR const fn is unstable
+pub const fn foo() -> usize { 22 }
+
+pub const fn bar() -> fn() {
+    fn x() {}
+    x
+}
+
+#[inline]
+pub const fn bar_inlined() -> fn() {
+    fn x() {}
+    x
+}
+
+#[inline(always)]
+pub const fn bar_inlined_always() -> fn() {
+    fn x() {}
+    x
+}

src/test/ui/consts/const_fn_return_nested_fn_ptr.rs

@@ -0,0 +1,10 @@
+// compile-pass
+// aux-build:const_fn_lib.rs
+
+extern crate const_fn_lib;
+
+fn main() {
+    const_fn_lib::bar()();
+    const_fn_lib::bar_inlined()();
+    const_fn_lib::bar_inlined_always()();
+}