use declarative macro for #[derive(TryFromU32)]

Author: fee1-dead

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -6,7 +6,6 @@ use rustc_abi::Align;
 use rustc_codegen_ssa::traits::{BaseTypeCodegenMethods, ConstCodegenMethods};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_index::IndexVec;
-use rustc_macros::TryFromU32;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::RemapFileNameExt;
 use rustc_session::config::RemapPathScopeComponents;
@@ -16,7 +15,7 @@ use tracing::debug;
 use crate::common::CodegenCx;
 use crate::coverageinfo::llvm_cov;
 use crate::coverageinfo::mapgen::covfun::prepare_covfun_record;
-use crate::llvm;
+use crate::{TryFromU32, llvm};
 
 mod covfun;
 mod spans;

compiler/rustc_codegen_llvm/src/lib.rs

@@ -14,6 +14,7 @@
 #![feature(if_let_guard)]
 #![feature(impl_trait_in_assoc_type)]
 #![feature(iter_intersperse)]
+#![feature(macro_derive)]
 #![feature(rustdoc_internals)]
 #![feature(slice_as_array)]
 #![feature(try_blocks)]
@@ -74,6 +75,25 @@ mod value;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
+// FIXME(fee1-dead) use `macro_attr` feature once that is available in bootstrap beta
+macro_rules! TryFromU32 {
+    derive() ($(#[$meta:meta])* $vis:vis enum $Type:ident {$(
+        $(#[$varmeta:meta])*
+        $Variant:ident $(= $discr:expr)?
+    ),*$(,)?}) => {
+        impl ::core::convert::TryFrom<u32> for $Type {
+            type Error = u32;
+            #[allow(deprecated)] // Don't warn about deprecated variants.
+            fn try_from(value: u32) -> ::core::result::Result<$Type, Self::Error> {
+                $( if value == const { $Type::$Variant as u32 } { return Ok($Type::$Variant) } )*
+                Err(value)
+            }
+        }
+    }
+}
+
+pub(crate) use TryFromU32;
+
 #[derive(Clone)]
 pub struct LlvmCodegenBackend(());
 

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -19,7 +19,6 @@ use std::ptr;
 
 use bitflags::bitflags;
 use libc::{c_char, c_int, c_uchar, c_uint, c_ulonglong, c_void, size_t};
-use rustc_macros::TryFromU32;
 use rustc_target::spec::SymbolVisibility;
 
 use super::RustString;
@@ -28,8 +27,8 @@ use super::debuginfo::{
     DIGlobalVariableExpression, DILocation, DISPFlags, DIScope, DISubprogram,
     DITemplateTypeParameter, DIType, DebugEmissionKind, DebugNameTableKind,
 };
-use crate::llvm;
 use crate::llvm::MetadataKindId;
+use crate::{TryFromU32, llvm};
 
 /// In the LLVM-C API, boolean values are passed as `typedef int LLVMBool`,
 /// which has a different ABI from Rust or C++ `bool`.

compiler/rustc_macros/src/lib.rs

@@ -18,7 +18,6 @@ mod print_attribute;
 mod query;
 mod serialize;
 mod symbols;
-mod try_from;
 mod type_foldable;
 mod type_visitable;
 mod visitable;
@@ -176,14 +175,6 @@ decl_derive!(
         applicability)] => diagnostics::subdiagnostic_derive
 );
 
-decl_derive! {
-    [TryFromU32] =>
-    /// Derives `TryFrom<u32>` for the annotated `enum`, which must have no fields.
-    /// Each variant maps to the value it would produce under an `as u32` cast.
-    ///
-    /// The error type is `u32`.
-    try_from::try_from_u32
-}
 decl_derive! {
     [PrintAttribute] =>
     /// Derives `PrintAttribute` for `AttributeKind`.