fn must be const if marked with stability attribut

remove trailing newline

fix: test with attribute but missing const

Update compiler/rustc_passes/src/stability.rs

Co-authored-by: Léo Lanteri Thauvin <leseulartichaut@gmail.com>

Add test for extern functions

fix: using span_help instead of span_suggestion

add test for some ABIs + fmt fix

Update compiler/rustc_passes/src/stability.rs

Co-authored-by: Léo Lanteri Thauvin <leseulartichaut@gmail.com>

Refractor and add test for `impl const`

Add test to make sure no output + cleanup condition

-----------------------------

remove stdcall test, failing CI test

C abi is already tested in this, so it is not that useful to test another one.
The tested code is blind to which specific ABI for now, as long as it's not an intrinsic one

compiler/rustc_error_codes/src/error_codes/E0542.md

@@ -10,7 +10,7 @@ Erroneous code example:
 fn _stable_fn() {}
 
 #[rustc_const_stable(feature = "_stable_const_fn")] // invalid
-fn _stable_const_fn() {}
+const fn _stable_const_fn() {}
 
 #[stable(feature = "_deprecated_fn", since = "0.1.0")]
 #[rustc_deprecated(
@@ -29,7 +29,7 @@ To fix this issue, you need to provide the `since` field. Example:
 fn _stable_fn() {}
 
 #[rustc_const_stable(feature = "_stable_const_fn", since = "1.0.0")] // ok!
-fn _stable_const_fn() {}
+const fn _stable_const_fn() {}
 
 #[stable(feature = "_deprecated_fn", since = "0.1.0")]
 #[rustc_deprecated(

compiler/rustc_error_codes/src/error_codes/E0545.md

@@ -10,7 +10,7 @@ Erroneous code example:
 fn _unstable_fn() {}
 
 #[rustc_const_unstable(feature = "_unstable_const_fn", issue = "0")] // invalid
-fn _unstable_const_fn() {}
+const fn _unstable_const_fn() {}
 ```
 
 To fix this issue, you need to provide a correct value in the `issue` field.
@@ -24,7 +24,7 @@ Example:
 fn _unstable_fn() {}
 
 #[rustc_const_unstable(feature = "_unstable_const_fn", issue = "1")] // ok!
-fn _unstable_const_fn() {}
+const fn _unstable_const_fn() {}
 ```
 
 See the [How Rust is Made and “Nightly Rust”][how-rust-made-nightly] appendix

compiler/rustc_error_codes/src/error_codes/E0547.md

@@ -10,7 +10,7 @@ Erroneous code example:
 fn _unstable_fn() {}
 
 #[rustc_const_unstable(feature = "_unstable_const_fn")] // invalid
-fn _unstable_const_fn() {}
+const fn _unstable_const_fn() {}
 ```
 
 To fix this issue, you need to provide the `issue` field. Example:
@@ -26,7 +26,7 @@ fn _unstable_fn() {}
     feature = "_unstable_const_fn",
     issue = "none"
 )] // ok!
-fn _unstable_const_fn() {}
+const fn _unstable_const_fn() {}
 ```
 
 See the [How Rust is Made and “Nightly Rust”][how-rust-made-nightly] appendix

compiler/rustc_passes/src/stability.rs

@@ -20,6 +20,7 @@ use rustc_session::parse::feature_err;
 use rustc_session::Session;
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
+use rustc_target::spec::abi::Abi;
 
 use std::cmp::Ordering;
 use std::iter;
@@ -95,10 +96,12 @@ struct Annotator<'a, 'tcx> {
 impl<'a, 'tcx> Annotator<'a, 'tcx> {
     // Determine the stability for a node based on its attributes and inherited
     // stability. The stability is recorded in the index and used as the parent.
+    // If the node is a function, `fn_sig` is its signature
     fn annotate<F>(
         &mut self,
         hir_id: HirId,
         item_sp: Span,
+        fn_sig: Option<&'tcx hir::FnSig<'tcx>>,
         kind: AnnotationKind,
         inherit_deprecation: InheritDeprecation,
         inherit_const_stability: InheritConstStability,
@@ -163,13 +166,30 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
         }
 
         let (stab, const_stab) = attr::find_stability(&self.tcx.sess, attrs, item_sp);
+        let mut const_span = None;
 
-        let const_stab = const_stab.map(|(const_stab, _)| {
+        let const_stab = const_stab.map(|(const_stab, const_span_node)| {
             let const_stab = self.tcx.intern_const_stability(const_stab);
             self.index.const_stab_map.insert(hir_id, const_stab);
+            const_span = Some(const_span_node);
             const_stab
         });
 
+        // If the current node is a function, has const stability attributes and if it doesn not have an intrinsic ABI,
+        // check if the function/method is const or the parent impl block is const
+        if let (Some(const_span), Some(fn_sig)) = (const_span, fn_sig) {
+            if fn_sig.header.abi != Abi::RustIntrinsic
+                && fn_sig.header.abi != Abi::PlatformIntrinsic
+                && !fn_sig.header.is_const()
+            {
+                if !self.in_trait_impl
+                    || (self.in_trait_impl && !self.tcx.is_const_fn_raw(hir_id.owner.to_def_id()))
+                {
+                    missing_const_err(&self.tcx.sess, fn_sig.span, const_span);
+                }
+            }
+        }
+
         // `impl const Trait for Type` items forward their const stability to their
         // immediate children.
         if const_stab.is_none() {
@@ -367,6 +387,8 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
         let orig_in_trait_impl = self.in_trait_impl;
         let mut kind = AnnotationKind::Required;
         let mut const_stab_inherit = InheritConstStability::No;
+        let mut fn_sig = None;
+
         match i.kind {
             // Inherent impls and foreign modules serve only as containers for other items,
             // they don't have their own stability. They still can be annotated as unstable
@@ -387,6 +409,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
                     self.annotate(
                         ctor_hir_id,
                         i.span,
+                        None,
                         AnnotationKind::Required,
                         InheritDeprecation::Yes,
                         InheritConstStability::No,
@@ -395,12 +418,16 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
                     )
                 }
             }
+            hir::ItemKind::Fn(ref item_fn_sig, _, _) => {
+                fn_sig = Some(item_fn_sig);
+            }
             _ => {}
         }
 
         self.annotate(
             i.hir_id(),
             i.span,
+            fn_sig,
             kind,
             InheritDeprecation::Yes,
             const_stab_inherit,
@@ -411,9 +438,15 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
     }
 
     fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) {
+        let fn_sig = match ti.kind {
+            hir::TraitItemKind::Fn(ref fn_sig, _) => Some(fn_sig),
+            _ => None,
+        };
+
         self.annotate(
             ti.hir_id(),
             ti.span,
+            fn_sig,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -427,9 +460,16 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
     fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) {
         let kind =
             if self.in_trait_impl { AnnotationKind::Prohibited } else { AnnotationKind::Required };
+
+        let fn_sig = match ii.kind {
+            hir::ImplItemKind::Fn(ref fn_sig, _) => Some(fn_sig),
+            _ => None,
+        };
+
         self.annotate(
             ii.hir_id(),
             ii.span,
+            fn_sig,
             kind,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -444,6 +484,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
         self.annotate(
             var.id,
             var.span,
+            None,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -453,6 +494,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
                     v.annotate(
                         ctor_hir_id,
                         var.span,
+                        None,
                         AnnotationKind::Required,
                         InheritDeprecation::Yes,
                         InheritConstStability::No,
@@ -470,6 +512,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
         self.annotate(
             s.hir_id,
             s.span,
+            None,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -484,6 +527,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
         self.annotate(
             i.hir_id(),
             i.span,
+            None,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -498,6 +542,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
         self.annotate(
             md.hir_id(),
             md.span,
+            None,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -517,6 +562,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
         self.annotate(
             p.hir_id,
             p.span,
+            None,
             kind,
             InheritDeprecation::No,
             InheritConstStability::No,
@@ -687,6 +733,7 @@ fn stability_index(tcx: TyCtxt<'tcx>, (): ()) -> Index<'tcx> {
         annotator.annotate(
             hir::CRATE_HIR_ID,
             krate.item.inner,
+            None,
             AnnotationKind::Required,
             InheritDeprecation::Yes,
             InheritConstStability::No,
@@ -969,3 +1016,15 @@ fn duplicate_feature_err(sess: &Session, span: Span, feature: Symbol) {
     struct_span_err!(sess, span, E0636, "the feature `{}` has already been declared", feature)
         .emit();
 }
+
+fn missing_const_err(session: &Session, fn_sig_span: Span, const_span: Span) {
+    const ERROR_MSG: &'static str = "attributes `#[rustc_const_unstable]` \
+         and `#[rustc_const_stable]` require \
+         the function or method to be `const`";
+
+    session
+        .struct_span_err(fn_sig_span, ERROR_MSG)
+        .span_help(fn_sig_span, "make the function or method const")
+        .span_label(const_span, "attribute specified here")
+        .emit();
+}

src/test/ui/consts/rustc-const-stability-require-const.rs

@@ -0,0 +1,47 @@
+#![crate_type = "lib"]
+#![feature(staged_api)]
+#![stable(feature = "foo", since = "1.0.0")]
+
+#[stable(feature = "foo", since = "1.0.0")]
+#[rustc_const_unstable(feature = "const_foo", issue = "none")]
+pub fn foo() {}
+//~^ ERROR attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+
+#[stable(feature = "bar", since = "1.0.0")]
+#[rustc_const_stable(feature = "const_bar", since = "1.0.0")]
+pub fn bar() {}
+//~^ ERROR attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+
+#[stable(feature = "potato", since = "1.0.0")]
+pub struct Potato;
+
+impl Potato {
+    #[stable(feature = "salad", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_salad", issue = "none")]
+    pub fn salad(&self) -> &'static str { "mmmmmm" }
+    //~^ ERROR attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+
+    #[stable(feature = "roasted", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_roasted", issue = "none")]
+    pub fn roasted(&self) -> &'static str { "mmmmmmmmmm" }
+    //~^ ERROR attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+}
+
+#[stable(feature = "bar", since = "1.0.0")]
+#[rustc_const_stable(feature = "const_bar", since = "1.0.0")]
+pub extern "C" fn bar_c() {}
+//~^ ERROR attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+
+#[stable(feature = "foo", since = "1.0.0")]
+#[rustc_const_unstable(feature = "const_foo", issue = "none")]
+pub extern "C" fn foo_c() {}
+//~^ ERROR attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+
+
+#[stable(feature = "foobar", since = "1.0.0")]
+#[rustc_const_unstable(feature = "foobar_const", issue = "none")]
+pub const fn foobar() {}
+
+#[stable(feature = "barfoo", since = "1.0.0")]
+#[rustc_const_stable(feature = "barfoo_const", since = "1.0.0")]
+pub const fn barfoo() {}

src/test/ui/consts/rustc-const-stability-require-const.stderr

@@ -0,0 +1,86 @@
+error: attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+  --> $DIR/rustc-const-stability-require-const.rs:7:1
+   |
+LL | #[rustc_const_unstable(feature = "const_foo", issue = "none")]
+   | -------------------------------------------------------------- attribute specified here
+LL | pub fn foo() {}
+   | ^^^^^^^^^^^^
+   |
+help: make the function or method const
+  --> $DIR/rustc-const-stability-require-const.rs:7:1
+   |
+LL | pub fn foo() {}
+   | ^^^^^^^^^^^^
+
+error: attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+  --> $DIR/rustc-const-stability-require-const.rs:12:1
+   |
+LL | #[rustc_const_stable(feature = "const_bar", since = "1.0.0")]
+   | ------------------------------------------------------------- attribute specified here
+LL | pub fn bar() {}
+   | ^^^^^^^^^^^^
+   |
+help: make the function or method const
+  --> $DIR/rustc-const-stability-require-const.rs:12:1
+   |
+LL | pub fn bar() {}
+   | ^^^^^^^^^^^^
+
+error: attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+  --> $DIR/rustc-const-stability-require-const.rs:21:5
+   |
+LL |     #[rustc_const_unstable(feature = "const_salad", issue = "none")]
+   |     ---------------------------------------------------------------- attribute specified here
+LL |     pub fn salad(&self) -> &'static str { "mmmmmm" }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function or method const
+  --> $DIR/rustc-const-stability-require-const.rs:21:5
+   |
+LL |     pub fn salad(&self) -> &'static str { "mmmmmm" }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+  --> $DIR/rustc-const-stability-require-const.rs:26:5
+   |
+LL |     #[rustc_const_unstable(feature = "const_roasted", issue = "none")]
+   |     ------------------------------------------------------------------ attribute specified here
+LL |     pub fn roasted(&self) -> &'static str { "mmmmmmmmmm" }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function or method const
+  --> $DIR/rustc-const-stability-require-const.rs:26:5
+   |
+LL |     pub fn roasted(&self) -> &'static str { "mmmmmmmmmm" }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+  --> $DIR/rustc-const-stability-require-const.rs:32:1
+   |
+LL | #[rustc_const_stable(feature = "const_bar", since = "1.0.0")]
+   | ------------------------------------------------------------- attribute specified here
+LL | pub extern "C" fn bar_c() {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function or method const
+  --> $DIR/rustc-const-stability-require-const.rs:32:1
+   |
+LL | pub extern "C" fn bar_c() {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
+  --> $DIR/rustc-const-stability-require-const.rs:37:1
+   |
+LL | #[rustc_const_unstable(feature = "const_foo", issue = "none")]
+   | -------------------------------------------------------------- attribute specified here
+LL | pub extern "C" fn foo_c() {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function or method const
+  --> $DIR/rustc-const-stability-require-const.rs:37:1
+   |
+LL | pub extern "C" fn foo_c() {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 6 previous errors
+

src/test/ui/consts/rustc-impl-const-stability.rs

@@ -0,0 +1,21 @@
+// build-pass
+
+#![crate_type = "lib"]
+#![allow(incomplete_features)]
+#![feature(staged_api)]
+#![feature(const_trait_impl)]
+#![stable(feature = "foo", since = "1.0.0")]
+
+
+#[stable(feature = "potato", since = "1.27.0")]
+pub struct Data {
+    _data: u128
+}
+
+#[stable(feature = "potato", since = "1.27.0")]
+impl const Default for Data {
+    #[rustc_const_unstable(feature = "data_foo", issue = "none")]
+    fn default() -> Data {
+        Data { _data: 42 }
+    }
+}