Produce an error when #[inline] and #[rust_force_inline] are used together

compiler/rustc_attr_parsing/src/attributes/inline.rs

@@ -1,12 +1,10 @@
-// FIXME(jdonszelmann): merge these two parsers and error when both attributes are present here.
-//                      note: need to model better how duplicate attr errors work when not using
-//                      SingleAttributeParser which is what we have two of here.
-
 use rustc_feature::AttributeStability;
 use rustc_hir::attrs::{AttributeKind, InlineAttr};
+use rustc_hir::find_attr;
 use rustc_session::lint::builtin::ILL_FORMED_ATTRIBUTE_INPUT;
 
 use super::prelude::*;
+use crate::session_diagnostics::InlineForceInlineConflict;
 
 pub(crate) struct InlineParser;
 
@@ -94,4 +92,16 @@ impl SingleAttributeParser for RustcForceInlineParser {
             cx.attr_span,
         ))
     }
+
+    fn finalize_check(cx: &FinalizeCheckContext<'_, '_>, attr_span: Span) {
+        let Some(inline_span) = find_attr!(cx.parsed_attrs, Inline(attr, span) if !matches!(attr, InlineAttr::Force { .. }) => span)
+        else {
+            return;
+        };
+
+        cx.emit_err(InlineForceInlineConflict {
+            inline_span: *inline_span,
+            force_inline_span: attr_span,
+        });
+    }
 }

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -13,6 +13,15 @@ use rustc_target::spec::TargetTuple;
 use crate::AttributeTemplate;
 use crate::context::Suggestion;
 
+#[derive(Diagnostic)]
+#[diag("`#[rustc_force_inline]` and `#[inline]` cannot be used together")]
+pub(crate) struct InlineForceInlineConflict {
+    #[primary_span]
+    pub force_inline_span: Span,
+    #[label("the inline attribute is specified here")]
+    pub inline_span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag("`#[ffi_const]` function cannot be `#[ffi_pure]`", code = E0757)]
 pub(crate) struct BothFfiConstAndPure {

tests/ui/attributes/inline/rustc-force-inline-conflict-with-inline.rs

@@ -0,0 +1,11 @@
+#![feature(rustc_attrs)]
+
+#[inline] //~ NOTE: the inline attribute is specified here
+#[rustc_force_inline] //~ ERROR: cannot be used together
+fn foo() {}
+
+#[rustc_force_inline] //~ ERROR: cannot be used together
+#[inline] //~ NOTE: the inline attribute is specified here
+fn bar() {}
+
+fn main() {}

tests/ui/attributes/inline/rustc-force-inline-conflict-with-inline.stderr

@@ -0,0 +1,18 @@
+error: `#[rustc_force_inline]` and `#[inline]` cannot be used together
+  --> $DIR/rustc-force-inline-conflict-with-inline.rs:4:1
+   |
+LL | #[inline]
+   | --------- the inline attribute is specified here
+LL | #[rustc_force_inline]
+   | ^^^^^^^^^^^^^^^^^^^^^
+
+error: `#[rustc_force_inline]` and `#[inline]` cannot be used together
+  --> $DIR/rustc-force-inline-conflict-with-inline.rs:7:1
+   |
+LL | #[rustc_force_inline]
+   | ^^^^^^^^^^^^^^^^^^^^^
+LL | #[inline]
+   | --------- the inline attribute is specified here
+
+error: aborting due to 2 previous errors
+