compiler/rustc_macros/src/diagnostics/subdiagnostic.rs

   1 #![deny(unused_must_use)]
   2
   3 use crate::diagnostics::error::{
   4     invalid_attr, span_err, throw_invalid_attr, throw_invalid_nested_attr, throw_span_err,
   5     DiagnosticDeriveError,
   6 };
   7 use crate::diagnostics::utils::{
   8     build_field_mapping, is_doc_comment, new_code_ident,
   9     report_error_if_not_applied_to_applicability, report_error_if_not_applied_to_span, FieldInfo,
  10     FieldInnerTy, FieldMap, HasFieldMap, SetOnce, SpannedOption, SubdiagnosticKind,
  11 };
  12 use proc_macro2::TokenStream;
  13 use quote::{format_ident, quote};
  14 use syn::{spanned::Spanned, Attribute, Meta, MetaList, NestedMeta, Path};
  15 use synstructure::{BindingInfo, Structure, VariantInfo};
  16
  17 use super::utils::{build_suggestion_code, AllowMultipleAlternatives};
  18
  19 /// The central struct for constructing the `add_to_diagnostic` method from an annotated struct.
  20 pub(crate) struct SubdiagnosticDeriveBuilder {
  21     diag: syn::Ident,
  22     f: syn::Ident,
  23 }
  24
  25 impl SubdiagnosticDeriveBuilder {
  26     pub(crate) fn new() -> Self {
  27         let diag = format_ident!("diag");
  28         let f = format_ident!("f");
  29         Self { diag, f }
  30     }
  31
  32     pub(crate) fn into_tokens(self, mut structure: Structure<'_>) -> TokenStream {
  33         let implementation = {
  34             let ast = structure.ast();
  35             let span = ast.span().unwrap();
  36             match ast.data {
  37                 syn::Data::Struct(..) | syn::Data::Enum(..) => (),
  38                 syn::Data::Union(..) => {
  39                     span_err(
  40                         span,
  41                         "`#[derive(Subdiagnostic)]` can only be used on structs and enums",
  42                     );
  43                 }
  44             }
  45
  46             let is_enum = matches!(ast.data, syn::Data::Enum(..));
  47             if is_enum {
  48                 for attr in &ast.attrs {
  49                     // Always allow documentation comments.
  50                     if is_doc_comment(attr) {
  51                         continue;
  52                     }
  53
  54                     span_err(
  55                         attr.span().unwrap(),
  56                         "unsupported type attribute for subdiagnostic enum",
  57                     )
  58                     .emit();
  59                 }
  60             }
  61
  62             structure.bind_with(|_| synstructure::BindStyle::Move);
  63             let variants_ = structure.each_variant(|variant| {
  64                 let mut builder = SubdiagnosticDeriveVariantBuilder {
  65                     parent: &self,
  66                     variant,
  67                     span,
  68                     formatting_init: TokenStream::new(),
  69                     fields: build_field_mapping(variant),
  70                     span_field: None,
  71                     applicability: None,
  72                     has_suggestion_parts: false,
  73                     is_enum,
  74                 };
  75                 builder.into_tokens().unwrap_or_else(|v| v.to_compile_error())
  76             });
  77
  78             quote! {
  79                 match self {
  80                     #variants_
  81                 }
  82             }
  83         };
  84
  85         let diag = &self.diag;
  86         let f = &self.f;
  87         let ret = structure.gen_impl(quote! {
  88             gen impl rustc_errors::AddToDiagnostic for @Self {
  89                 fn add_to_diagnostic_with<__F>(self, #diag: &mut rustc_errors::Diagnostic, #f: __F)
  90                 where
  91                     __F: core::ops::Fn(
  92                         &mut rustc_errors::Diagnostic,
  93                         rustc_errors::SubdiagnosticMessage
  94                     ) -> rustc_errors::SubdiagnosticMessage,
  95                 {
  96                     use rustc_errors::{Applicability, IntoDiagnosticArg};
  97                     #implementation
  98                 }
  99             }
 100         });
 101         ret
 102     }
 103 }
 104
 105 /// Tracks persistent information required for building up the call to add to the diagnostic
 106 /// for the final generated method. This is a separate struct to `SubdiagnosticDerive`
 107 /// only to be able to destructure and split `self.builder` and the `self.structure` up to avoid a
 108 /// double mut borrow later on.
 109 struct SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
 110     /// The identifier to use for the generated `DiagnosticBuilder` instance.
 111     parent: &'parent SubdiagnosticDeriveBuilder,
 112
 113     /// Info for the current variant (or the type if not an enum).
 114     variant: &'a VariantInfo<'a>,
 115     /// Span for the entire type.
 116     span: proc_macro::Span,
 117
 118     /// Initialization of format strings for code suggestions.
 119     formatting_init: TokenStream,
 120
 121     /// Store a map of field name to its corresponding field. This is built on construction of the
 122     /// derive builder.
 123     fields: FieldMap,
 124
 125     /// Identifier for the binding to the `#[primary_span]` field.
 126     span_field: SpannedOption<proc_macro2::Ident>,
 127
 128     /// The binding to the `#[applicability]` field, if present.
 129     applicability: SpannedOption<TokenStream>,
 130
 131     /// Set to true when a `#[suggestion_part]` field is encountered, used to generate an error
 132     /// during finalization if still `false`.
 133     has_suggestion_parts: bool,
 134
 135     /// Set to true when this variant is an enum variant rather than just the body of a struct.
 136     is_enum: bool,
 137 }
 138
 139 impl<'parent, 'a> HasFieldMap for SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
 140     fn get_field_binding(&self, field: &String) -> Option<&TokenStream> {
 141         self.fields.get(field)
 142     }
 143 }
 144
 145 /// Provides frequently-needed information about the diagnostic kinds being derived for this type.
 146 #[derive(Clone, Copy, Debug)]
 147 struct KindsStatistics {
 148     has_multipart_suggestion: bool,
 149     all_multipart_suggestions: bool,
 150     has_normal_suggestion: bool,
 151     all_applicabilities_static: bool,
 152 }
 153
 154 impl<'a> FromIterator<&'a SubdiagnosticKind> for KindsStatistics {
 155     fn from_iter<T: IntoIterator<Item = &'a SubdiagnosticKind>>(kinds: T) -> Self {
 156         let mut ret = Self {
 157             has_multipart_suggestion: false,
 158             all_multipart_suggestions: true,
 159             has_normal_suggestion: false,
 160             all_applicabilities_static: true,
 161         };
 162
 163         for kind in kinds {
 164             if let SubdiagnosticKind::MultipartSuggestion { applicability: None, .. }
 165             | SubdiagnosticKind::Suggestion { applicability: None, .. } = kind
 166             {
 167                 ret.all_applicabilities_static = false;
 168             }
 169             if let SubdiagnosticKind::MultipartSuggestion { .. } = kind {
 170                 ret.has_multipart_suggestion = true;
 171             } else {
 172                 ret.all_multipart_suggestions = false;
 173             }
 174
 175             if let SubdiagnosticKind::Suggestion { .. } = kind {
 176                 ret.has_normal_suggestion = true;
 177             }
 178         }
 179         ret
 180     }
 181 }
 182
 183 impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
 184     fn identify_kind(&mut self) -> Result<Vec<(SubdiagnosticKind, Path)>, DiagnosticDeriveError> {
 185         let mut kind_slugs = vec![];
 186
 187         for attr in self.variant.ast().attrs {
 188             let Some((kind, slug)) = SubdiagnosticKind::from_attr(attr, self)? else {
 189                 // Some attributes aren't errors - like documentation comments - but also aren't
 190                 // subdiagnostics.
 191                 continue;
 192             };
 193
 194             let Some(slug) = slug else {
 195                 let name = attr.path.segments.last().unwrap().ident.to_string();
 196                 let name = name.as_str();
 197
 198                 throw_span_err!(
 199                     attr.span().unwrap(),
 200                     &format!(
 201                         "diagnostic slug must be first argument of a `#[{name}(...)]` attribute"
 202                     )
 203                 );
 204             };
 205
 206             kind_slugs.push((kind, slug));
 207         }
 208
 209         Ok(kind_slugs)
 210     }
 211
 212     /// Generates the code for a field with no attributes.
 213     fn generate_field_set_arg(&mut self, binding: &BindingInfo<'_>) -> TokenStream {
 214         let ast = binding.ast();
 215         assert_eq!(ast.attrs.len(), 0, "field with attribute used as diagnostic arg");
 216
 217         let diag = &self.parent.diag;
 218         let ident = ast.ident.as_ref().unwrap();
 219         // strip `r#` prefix, if present
 220         let ident = format_ident!("{}", ident);
 221
 222         quote! {
 223             #diag.set_arg(
 224                 stringify!(#ident),
 225                 #binding
 226             );
 227         }
 228     }
 229
 230     /// Generates the necessary code for all attributes on a field.
 231     fn generate_field_attr_code(
 232         &mut self,
 233         binding: &BindingInfo<'_>,
 234         kind_stats: KindsStatistics,
 235     ) -> TokenStream {
 236         let ast = binding.ast();
 237         assert!(ast.attrs.len() > 0, "field without attributes generating attr code");
 238
 239         // Abstract over `Vec<T>` and `Option<T>` fields using `FieldInnerTy`, which will
 240         // apply the generated code on each element in the `Vec` or `Option`.
 241         let inner_ty = FieldInnerTy::from_type(&ast.ty);
 242         ast.attrs
 243             .iter()
 244             .map(|attr| {
 245                 // Always allow documentation comments.
 246                 if is_doc_comment(attr) {
 247                     return quote! {};
 248                 }
 249
 250                 let info = FieldInfo {
 251                     binding,
 252                     ty: inner_ty.inner_type().unwrap_or(&ast.ty),
 253                     span: &ast.span(),
 254                 };
 255
 256                 let generated = self
 257                     .generate_field_code_inner(kind_stats, attr, info, inner_ty.will_iterate())
 258                     .unwrap_or_else(|v| v.to_compile_error());
 259
 260                 inner_ty.with(binding, generated)
 261             })
 262             .collect()
 263     }
 264
 265     fn generate_field_code_inner(
 266         &mut self,
 267         kind_stats: KindsStatistics,
 268         attr: &Attribute,
 269         info: FieldInfo<'_>,
 270         clone_suggestion_code: bool,
 271     ) -> Result<TokenStream, DiagnosticDeriveError> {
 272         let meta = attr.parse_meta()?;
 273         match meta {
 274             Meta::Path(path) => self.generate_field_code_inner_path(kind_stats, attr, info, path),
 275             Meta::List(list @ MetaList { .. }) => self.generate_field_code_inner_list(
 276                 kind_stats,
 277                 attr,
 278                 info,
 279                 list,
 280                 clone_suggestion_code,
 281             ),
 282             _ => throw_invalid_attr!(attr, &meta),
 283         }
 284     }
 285
 286     /// Generates the code for a `[Meta::Path]`-like attribute on a field (e.g. `#[primary_span]`).
 287     fn generate_field_code_inner_path(
 288         &mut self,
 289         kind_stats: KindsStatistics,
 290         attr: &Attribute,
 291         info: FieldInfo<'_>,
 292         path: Path,
 293     ) -> Result<TokenStream, DiagnosticDeriveError> {
 294         let span = attr.span().unwrap();
 295         let ident = &path.segments.last().unwrap().ident;
 296         let name = ident.to_string();
 297         let name = name.as_str();
 298
 299         match name {
 300             "skip_arg" => Ok(quote! {}),
 301             "primary_span" => {
 302                 if kind_stats.has_multipart_suggestion {
 303                     invalid_attr(attr, &Meta::Path(path))
 304                         .help(
 305                             "multipart suggestions use one or more `#[suggestion_part]`s rather \
 306                             than one `#[primary_span]`",
 307                         )
 308                         .emit();
 309                 } else {
 310                     report_error_if_not_applied_to_span(attr, &info)?;
 311
 312                     let binding = info.binding.binding.clone();
 313                     // FIXME(#100717): support `Option<Span>` on `primary_span` like in the
 314                     // diagnostic derive
 315                     self.span_field.set_once(binding, span);
 316                 }
 317
 318                 Ok(quote! {})
 319             }
 320             "suggestion_part" => {
 321                 self.has_suggestion_parts = true;
 322
 323                 if kind_stats.has_multipart_suggestion {
 324                     span_err(span, "`#[suggestion_part(...)]` attribute without `code = \"...\"`")
 325                         .emit();
 326                 } else {
 327                     invalid_attr(attr, &Meta::Path(path))
 328                         .help(
 329                             "`#[suggestion_part(...)]` is only valid in multipart suggestions, \
 330                              use `#[primary_span]` instead",
 331                         )
 332                         .emit();
 333                 }
 334
 335                 Ok(quote! {})
 336             }
 337             "applicability" => {
 338                 if kind_stats.has_multipart_suggestion || kind_stats.has_normal_suggestion {
 339                     report_error_if_not_applied_to_applicability(attr, &info)?;
 340
 341                     if kind_stats.all_applicabilities_static {
 342                         span_err(
 343                             span,
 344                             "`#[applicability]` has no effect if all `#[suggestion]`/\
 345                              `#[multipart_suggestion]` attributes have a static \
 346                              `applicability = \"...\"`",
 347                         )
 348                         .emit();
 349                     }
 350                     let binding = info.binding.binding.clone();
 351                     self.applicability.set_once(quote! { #binding }, span);
 352                 } else {
 353                     span_err(span, "`#[applicability]` is only valid on suggestions").emit();
 354                 }
 355
 356                 Ok(quote! {})
 357             }
 358             _ => {
 359                 let mut span_attrs = vec![];
 360                 if kind_stats.has_multipart_suggestion {
 361                     span_attrs.push("suggestion_part");
 362                 }
 363                 if !kind_stats.all_multipart_suggestions {
 364                     span_attrs.push("primary_span")
 365                 }
 366
 367                 invalid_attr(attr, &Meta::Path(path))
 368                     .help(format!(
 369                         "only `{}`, `applicability` and `skip_arg` are valid field attributes",
 370                         span_attrs.join(", ")
 371                     ))
 372                     .emit();
 373
 374                 Ok(quote! {})
 375             }
 376         }
 377     }
 378
 379     /// Generates the code for a `[Meta::List]`-like attribute on a field (e.g.
 380     /// `#[suggestion_part(code = "...")]`).
 381     fn generate_field_code_inner_list(
 382         &mut self,
 383         kind_stats: KindsStatistics,
 384         attr: &Attribute,
 385         info: FieldInfo<'_>,
 386         list: MetaList,
 387         clone_suggestion_code: bool,
 388     ) -> Result<TokenStream, DiagnosticDeriveError> {
 389         let span = attr.span().unwrap();
 390         let ident = &list.path.segments.last().unwrap().ident;
 391         let name = ident.to_string();
 392         let name = name.as_str();
 393
 394         match name {
 395             "suggestion_part" => {
 396                 if !kind_stats.has_multipart_suggestion {
 397                     throw_invalid_attr!(attr, &Meta::List(list), |diag| {
 398                         diag.help(
 399                             "`#[suggestion_part(...)]` is only valid in multipart suggestions",
 400                         )
 401                     })
 402                 }
 403
 404                 self.has_suggestion_parts = true;
 405
 406                 report_error_if_not_applied_to_span(attr, &info)?;
 407
 408                 let mut code = None;
 409                 for nested_attr in list.nested.iter() {
 410                     let NestedMeta::Meta(ref meta) = nested_attr else {
 411                         throw_invalid_nested_attr!(attr, nested_attr);
 412                     };
 413
 414                     let span = meta.span().unwrap();
 415                     let nested_name = meta.path().segments.last().unwrap().ident.to_string();
 416                     let nested_name = nested_name.as_str();
 417
 418                     match nested_name {
 419                         "code" => {
 420                             let code_field = new_code_ident();
 421                             let formatting_init = build_suggestion_code(
 422                                 &code_field,
 423                                 meta,
 424                                 self,
 425                                 AllowMultipleAlternatives::No,
 426                             );
 427                             code.set_once((code_field, formatting_init), span);
 428                         }
 429                         _ => throw_invalid_nested_attr!(attr, nested_attr, |diag| {
 430                             diag.help("`code` is the only valid nested attribute")
 431                         }),
 432                     }
 433                 }
 434
 435                 let Some((code_field, formatting_init)) = code.value() else {
 436                     span_err(span, "`#[suggestion_part(...)]` attribute without `code = \"...\"`")
 437                         .emit();
 438                     return Ok(quote! {});
 439                 };
 440                 let binding = info.binding;
 441
 442                 self.formatting_init.extend(formatting_init);
 443                 let code_field = if clone_suggestion_code {
 444                     quote! { #code_field.clone() }
 445                 } else {
 446                     quote! { #code_field }
 447                 };
 448                 Ok(quote! { suggestions.push((#binding, #code_field)); })
 449             }
 450             _ => throw_invalid_attr!(attr, &Meta::List(list), |diag| {
 451                 let mut span_attrs = vec![];
 452                 if kind_stats.has_multipart_suggestion {
 453                     span_attrs.push("suggestion_part");
 454                 }
 455                 if !kind_stats.all_multipart_suggestions {
 456                     span_attrs.push("primary_span")
 457                 }
 458                 diag.help(format!(
 459                     "only `{}`, `applicability` and `skip_arg` are valid field attributes",
 460                     span_attrs.join(", ")
 461                 ))
 462             }),
 463         }
 464     }
 465
 466     pub fn into_tokens(&mut self) -> Result<TokenStream, DiagnosticDeriveError> {
 467         let kind_slugs = self.identify_kind()?;
 468         if kind_slugs.is_empty() {
 469             if self.is_enum {
 470                 // It's okay for a variant to not be a subdiagnostic at all..
 471                 return Ok(quote! {});
 472             } else {
 473                 // ..but structs should always be _something_.
 474                 throw_span_err!(
 475                     self.variant.ast().ident.span().unwrap(),
 476                     "subdiagnostic kind not specified"
 477                 );
 478             }
 479         };
 480
 481         let kind_stats: KindsStatistics = kind_slugs.iter().map(|(kind, _slug)| kind).collect();
 482
 483         let init = if kind_stats.has_multipart_suggestion {
 484             quote! { let mut suggestions = Vec::new(); }
 485         } else {
 486             quote! {}
 487         };
 488
 489         let attr_args: TokenStream = self
 490             .variant
 491             .bindings()
 492             .iter()
 493             .filter(|binding| !binding.ast().attrs.is_empty())
 494             .map(|binding| self.generate_field_attr_code(binding, kind_stats))
 495             .collect();
 496
 497         let span_field = self.span_field.value_ref();
 498
 499         let diag = &self.parent.diag;
 500         let f = &self.parent.f;
 501         let mut calls = TokenStream::new();
 502         for (kind, slug) in kind_slugs {
 503             let message = format_ident!("__message");
 504             calls.extend(quote! { let #message = #f(#diag, rustc_errors::fluent::#slug.into()); });
 505
 506             let name = format_ident!("{}{}", if span_field.is_some() { "span_" } else { "" }, kind);
 507             let call = match kind {
 508                 SubdiagnosticKind::Suggestion {
 509                     suggestion_kind,
 510                     applicability,
 511                     code_init,
 512                     code_field,
 513                 } => {
 514                     self.formatting_init.extend(code_init);
 515
 516                     let applicability = applicability
 517                         .value()
 518                         .map(|a| quote! { #a })
 519                         .or_else(|| self.applicability.take().value())
 520                         .unwrap_or_else(|| quote! { rustc_errors::Applicability::Unspecified });
 521
 522                     if let Some(span) = span_field {
 523                         let style = suggestion_kind.to_suggestion_style();
 524                         quote! { #diag.#name(#span, #message, #code_field, #applicability, #style); }
 525                     } else {
 526                         span_err(self.span, "suggestion without `#[primary_span]` field").emit();
 527                         quote! { unreachable!(); }
 528                     }
 529                 }
 530                 SubdiagnosticKind::MultipartSuggestion { suggestion_kind, applicability } => {
 531                     let applicability = applicability
 532                         .value()
 533                         .map(|a| quote! { #a })
 534                         .or_else(|| self.applicability.take().value())
 535                         .unwrap_or_else(|| quote! { rustc_errors::Applicability::Unspecified });
 536
 537                     if !self.has_suggestion_parts {
 538                         span_err(
 539                             self.span,
 540                             "multipart suggestion without any `#[suggestion_part(...)]` fields",
 541                         )
 542                         .emit();
 543                     }
 544
 545                     let style = suggestion_kind.to_suggestion_style();
 546
 547                     quote! { #diag.#name(#message, suggestions, #applicability, #style); }
 548                 }
 549                 SubdiagnosticKind::Label => {
 550                     if let Some(span) = span_field {
 551                         quote! { #diag.#name(#span, #message); }
 552                     } else {
 553                         span_err(self.span, "label without `#[primary_span]` field").emit();
 554                         quote! { unreachable!(); }
 555                     }
 556                 }
 557                 _ => {
 558                     if let Some(span) = span_field {
 559                         quote! { #diag.#name(#span, #message); }
 560                     } else {
 561                         quote! { #diag.#name(#message); }
 562                     }
 563                 }
 564             };
 565
 566             calls.extend(call);
 567         }
 568
 569         let plain_args: TokenStream = self
 570             .variant
 571             .bindings()
 572             .iter()
 573             .filter(|binding| binding.ast().attrs.is_empty())
 574             .map(|binding| self.generate_field_set_arg(binding))
 575             .collect();
 576
 577         let formatting_init = &self.formatting_init;
 578         Ok(quote! {
 579             #init
 580             #formatting_init
 581             #attr_args
 582             #plain_args
 583             #calls
 584         })
 585     }
 586 }