Rollup merge of #98276 - compiler-errors:const-format-macro, r=oli-obk

Mention formatting macros when encountering `ArgumentV1` method in const

Also open to just closing this if it's overkill. There are a lot of other distracting error messages around, so maybe it's not worth fixing just this one.

Fixes #93665

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -10,7 +10,8 @@ use rustc_middle::mir;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
 use rustc_middle::ty::{
-    suggest_constraining_type_param, Adt, Closure, FnDef, FnPtr, Param, TraitPredicate, Ty,
+    suggest_constraining_type_param, Adt, Closure, DefIdTree, FnDef, FnPtr, Param, TraitPredicate,
+    Ty,
 };
 use rustc_middle::ty::{Binder, BoundConstness, ImplPolarity, TraitRef};
 use rustc_session::parse::feature_err;
@@ -300,6 +301,15 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                 diag_trait(&mut err, self_ty, tcx.lang_items().deref_trait().unwrap());
                 err
             }
+            _ if tcx.opt_parent(callee) == tcx.get_diagnostic_item(sym::ArgumentV1Methods) => {
+                struct_span_err!(
+                    ccx.tcx.sess,
+                    span,
+                    E0015,
+                    "cannot call non-const formatting macro in {}s",
+                    ccx.const_kind(),
+                )
+            }
             _ => struct_span_err!(
                 ccx.tcx.sess,
                 span,

compiler/rustc_span/src/symbol.rs

@@ -131,6 +131,7 @@ symbols! {
         Arc,
         Argument,
         ArgumentV1,
+        ArgumentV1Methods,
         Arguments,
         AsMut,
         AsRef,

library/core/src/fmt/mod.rs

@@ -320,6 +320,7 @@ macro_rules! arg_new {
     };
 }
 
+#[rustc_diagnostic_item = "ArgumentV1Methods"]
 impl<'a> ArgumentV1<'a> {
     #[doc(hidden)]
     #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]

src/test/ui/consts/const-eval/format.rs

@@ -0,0 +1,21 @@
+const fn failure() {
+    panic!("{:?}", 0);
+    //~^ ERROR cannot call non-const formatting macro in constant functions
+    //~| ERROR erroneous constant used
+    //~| ERROR erroneous constant used
+    //~| WARN this was previously accepted by the compiler
+    //~| WARN this was previously accepted by the compiler
+}
+
+const fn print() {
+    println!("{:?}", 0);
+    //~^ ERROR cannot call non-const formatting macro in constant functions
+    //~| ERROR `Arguments::<'a>::new_v1` is not yet stable as a const fn
+    //~| ERROR cannot call non-const fn `_print` in constant functions
+    //~| ERROR erroneous constant used
+    //~| ERROR erroneous constant used
+    //~| WARN this was previously accepted by the compiler
+    //~| WARN this was previously accepted by the compiler
+}
+
+fn main() {}

src/test/ui/consts/const-eval/format.stderr

@@ -0,0 +1,78 @@
+error[E0015]: cannot call non-const formatting macro in constant functions
+  --> $DIR/format.rs:2:20
+   |
+LL |     panic!("{:?}", 0);
+   |                    ^
+   |
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+   = note: this error originates in the macro `$crate::const_format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0015]: cannot call non-const formatting macro in constant functions
+  --> $DIR/format.rs:11:22
+   |
+LL |     println!("{:?}", 0);
+   |                      ^
+   |
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: `Arguments::<'a>::new_v1` is not yet stable as a const fn
+  --> $DIR/format.rs:11:5
+   |
+LL |     println!("{:?}", 0);
+   |     ^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(const_fmt_arguments_new)]` to the crate attributes to enable
+   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0015]: cannot call non-const fn `_print` in constant functions
+  --> $DIR/format.rs:11:5
+   |
+LL |     println!("{:?}", 0);
+   |     ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+   = note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: erroneous constant used
+  --> $DIR/format.rs:2:12
+   |
+LL |     panic!("{:?}", 0);
+   |            ^^^^^^ referenced constant has errors
+   |
+   = note: `#[deny(const_err)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
+error: erroneous constant used
+  --> $DIR/format.rs:2:20
+   |
+LL |     panic!("{:?}", 0);
+   |                    ^ referenced constant has errors
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+   = note: this error originates in the macro `$crate::const_format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: erroneous constant used
+  --> $DIR/format.rs:11:14
+   |
+LL |     println!("{:?}", 0);
+   |              ^^^^^^ referenced constant has errors
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
+error: erroneous constant used
+  --> $DIR/format.rs:11:22
+   |
+LL |     println!("{:?}", 0);
+   |                      ^ referenced constant has errors
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 8 previous errors
+
+For more information about this error, try `rustc --explain E0015`.