Rollup merge of #138231 - Sa4dUs:autodiff-ice, r=ZuseZ4

Prevent ICE in autodiff validation by emitting user-friendly errors

This PR moves `valid_ret_activity` and `valid_input_activity` checks to the macro expansion phase in compiler/rustc_builtin_macros/src/autodiff.rs, replacing the following internal compiler error (ICE):
```
error: internal compiler error:
compiler/rustc_codegen_ssa/src/codegen_attrs.rs:935:13:
Invalid input activity Dual for Reverse mode
```
with a more user-friendly message.

The issue specifically affected the test file `tests/ui/autodiff/autodiff_illegal.rs`, impacting the functions `f5` and `f6`.

The ICE can be reproduced by following [Enzyme's Rustbook](https://enzymead.github.io/rustbook/installation.html) installation guide.

Additionally, this PR adds tests for invalid return activity in `autodiff_illegal.rs`, which previously triggered an unnoticed ICE before these fixes.

r? ``@oli-obk``

1 files changed, 1 insertions, 12 deletions

diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 90c53c34768..27b8be1022e 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -1,9 +1,7 @@
 use std::str::FromStr;
 
 use rustc_abi::ExternAbi;
-use rustc_ast::expand::autodiff_attrs::{
-    AutoDiffAttrs, DiffActivity, DiffMode, valid_input_activity, valid_ret_activity,
-};
+use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
 use rustc_ast::{MetaItem, MetaItemInner, attr};
 use rustc_attr_parsing::ReprAttr::ReprAlign;
 use rustc_attr_parsing::{AttributeKind, InlineAttr, InstructionSetAttr, OptimizeAttr};
@@ -874,15 +872,6 @@ fn autodiff_attrs(tcx: TyCtxt<'_>, id: DefId) -> Option<AutoDiffAttrs> {
         }
     }
 
-    for &input in &arg_activities {
-        if !valid_input_activity(mode, input) {
-            span_bug!(attr.span(), "Invalid input activity {} for {} mode", input, mode);
-        }
-    }
-    if !valid_ret_activity(mode, ret_activity) {
-        span_bug!(attr.span(), "Invalid return activity {} for {} mode", ret_activity, mode);
-    }
-
     Some(AutoDiffAttrs { mode, ret_activity, input_activity: arg_activities })
 }