Rollup merge of #136239 - folkertdev:show-supported-register-classes, r=SparrowLii,jieyouxu

show supported register classes in error message

a simple diagnostic change that shows the supported register classes when an invalid one is found.

This information can be hard to find (especially for unstable targets), and this message now gives at least something to try or search for. I've followed the pattern for invalid clobber ABIs.

`@rustbot` label +A-inline-assembly

compiler/rustc_ast_lowering/messages.ftl

@@ -112,7 +112,8 @@ ast_lowering_invalid_register =
     invalid register `{$reg}`: {$error}
 
 ast_lowering_invalid_register_class =
-    invalid register class `{$reg_class}`: {$error}
+    invalid register class `{$reg_class}`: unknown register class
+    .note = the following register classes are supported on this target: {$supported_register_classes}
 
 ast_lowering_match_arm_with_no_body =
     `match` arm with no body

compiler/rustc_ast_lowering/src/asm.rs

@@ -152,11 +152,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     InlineAsmRegOrRegClass::RegClass(reg_class) => {
                         asm::InlineAsmRegOrRegClass::RegClass(if let Some(asm_arch) = asm_arch {
                             asm::InlineAsmRegClass::parse(asm_arch, reg_class).unwrap_or_else(
-                                |error| {
+                                |supported_register_classes| {
+                                    let mut register_classes =
+                                        format!("`{}`", supported_register_classes[0]);
+                                    for m in &supported_register_classes[1..] {
+                                        let _ = write!(register_classes, ", `{m}`");
+                                    }
                                     self.dcx().emit_err(InvalidRegisterClass {
                                         op_span: *op_sp,
                                         reg_class,
-                                        error,
+                                        supported_register_classes: register_classes,
                                     });
                                     asm::InlineAsmRegClass::Err
                                 },

compiler/rustc_ast_lowering/src/errors.rs

@@ -197,12 +197,13 @@ pub(crate) struct InvalidRegister<'a> {
 }
 
 #[derive(Diagnostic)]
+#[note]
 #[diag(ast_lowering_invalid_register_class)]
-pub(crate) struct InvalidRegisterClass<'a> {
+pub(crate) struct InvalidRegisterClass {
     #[primary_span]
     pub op_span: Span,
     pub reg_class: Symbol,
-    pub error: &'a str,
+    pub supported_register_classes: String,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_target/src/asm/mod.rs

@@ -39,12 +39,12 @@ macro_rules! def_reg_class {
                 }
             }
 
-            pub fn parse(name: rustc_span::Symbol) -> Result<Self, &'static str> {
+            pub fn parse(name: rustc_span::Symbol) -> Result<Self, &'static [rustc_span::Symbol]> {
                 match name {
                     $(
                         rustc_span::sym::$class => Ok(Self::$class),
                     )*
-                    _ => Err("unknown register class"),
+                    _ => Err(&[$(rustc_span::sym::$class),*]),
                 }
             }
         }
@@ -635,7 +635,7 @@ impl InlineAsmRegClass {
         }
     }
 
-    pub fn parse(arch: InlineAsmArch, name: Symbol) -> Result<Self, &'static str> {
+    pub fn parse(arch: InlineAsmArch, name: Symbol) -> Result<Self, &'static [rustc_span::Symbol]> {
         Ok(match arch {
             InlineAsmArch::X86 | InlineAsmArch::X86_64 => {
                 Self::X86(X86InlineAsmRegClass::parse(name)?)