Allow comptime fns to call other comptime fns

Author: oli-obk

compiler/rustc_middle/src/hir/map.rs

@@ -319,7 +319,11 @@ impl<'tcx> TyCtxt<'tcx> {
 
             BodyOwnerKind::Fn if self.is_constructor(def_id) => return None,
             BodyOwnerKind::Fn | BodyOwnerKind::Closure if self.is_const_fn(def_id) => {
-                ConstContext::ConstFn
+                if self.constness(def_id) == rustc_hir::Constness::Comptime {
+                    ConstContext::Const { inline: true }
+                } else {
+                    ConstContext::ConstFn
+                }
             }
             BodyOwnerKind::Fn if self.is_const_default_method(def_id) => ConstContext::ConstFn,
             BodyOwnerKind::Fn | BodyOwnerKind::Closure | BodyOwnerKind::GlobalAsm => return None,

tests/ui/comptime/not_callable.rs

@@ -19,7 +19,6 @@ const fn bar() {
 
 #[rustc_comptime]
 fn baz() {
-    // Should be allowed
+    // Ok
     foo();
-    //~^ ERROR: comptime fns can only be called at compile time
 }

tests/ui/comptime/not_callable.stderr

@@ -10,11 +10,5 @@ error: comptime fns can only be called at compile time
 LL |     foo();
    |     ^^^^^
 
-error: comptime fns can only be called at compile time
-  --> $DIR/not_callable.rs:23:5
-   |
-LL |     foo();
-   |     ^^^^^
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors