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<'a>(self, mut structure: Structure<'a>) -> 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 `#[{}(...)]` attribute",
 202                         name
 203                     )
 204                 );
 205             };
 206
 207             kind_slugs.push((kind, slug));
 208         }
 209
 210         Ok(kind_slugs)
 211     }
 212
 213     /// Generates the code for a field with no attributes.
 214     fn generate_field_set_arg(&mut self, binding: &BindingInfo<'_>) -> TokenStream {
 215         let ast = binding.ast();
 216         assert_eq!(ast.attrs.len(), 0, "field with attribute used as diagnostic arg");
 217
 218         let diag = &self.parent.diag;
 219         let ident = ast.ident.as_ref().unwrap();
 220         // strip `r#` prefix, if present
 221         let ident = format_ident!("{}", ident);
 222
 223         quote! {
 224             #diag.set_arg(
 225                 stringify!(#ident),
 226                 #binding
 227             );
 228         }
 229     }
 230
 231     /// Generates the necessary code for all attributes on a field.
 232     fn generate_field_attr_code(
 233         &mut self,
 234         binding: &BindingInfo<'_>,
 235         kind_stats: KindsStatistics,
 236     ) -> TokenStream {
 237         let ast = binding.ast();
 238         assert!(ast.attrs.len() > 0, "field without attributes generating attr code");
 239
 240         // Abstract over `Vec<T>` and `Option<T>` fields using `FieldInnerTy`, which will
 241         // apply the generated code on each element in the `Vec` or `Option`.
 242         let inner_ty = FieldInnerTy::from_type(&ast.ty);
 243         ast.attrs
 244             .iter()
 245             .map(|attr| {
 246                 // Always allow documentation comments.
 247                 if is_doc_comment(attr) {
 248                     return quote! {};
 249                 }
 250
 251                 let info = FieldInfo {
 252                     binding,
 253                     ty: inner_ty.inner_type().unwrap_or(&ast.ty),
 254                     span: &ast.span(),
 255                 };
 256
 257                 let generated = self
 258                     .generate_field_code_inner(kind_stats, attr, info, inner_ty.will_iterate())
 259                     .unwrap_or_else(|v| v.to_compile_error());
 260
 261                 inner_ty.with(binding, generated)
 262             })
 263             .collect()
 264     }
 265
 266     fn generate_field_code_inner(
 267         &mut self,
 268         kind_stats: KindsStatistics,
 269         attr: &Attribute,
 270         info: FieldInfo<'_>,
 271         clone_suggestion_code: bool,
 272     ) -> Result<TokenStream, DiagnosticDeriveError> {
 273         let meta = attr.parse_meta()?;
 274         match meta {
 275             Meta::Path(path) => self.generate_field_code_inner_path(kind_stats, attr, info, path),
 276             Meta::List(list @ MetaList { .. }) => self.generate_field_code_inner_list(
 277                 kind_stats,
 278                 attr,
 279                 info,
 280                 list,
 281                 clone_suggestion_code,
 282             ),
 283             _ => throw_invalid_attr!(attr, &meta),
 284         }
 285     }
 286
 287     /// Generates the code for a `[Meta::Path]`-like attribute on a field (e.g. `#[primary_span]`).
 288     fn generate_field_code_inner_path(
 289         &mut self,
 290         kind_stats: KindsStatistics,
 291         attr: &Attribute,
 292         info: FieldInfo<'_>,
 293         path: Path,
 294     ) -> Result<TokenStream, DiagnosticDeriveError> {
 295         let span = attr.span().unwrap();
 296         let ident = &path.segments.last().unwrap().ident;
 297         let name = ident.to_string();
 298         let name = name.as_str();
 299
 300         match name {
 301             "skip_arg" => Ok(quote! {}),
 302             "primary_span" => {
 303                 if kind_stats.has_multipart_suggestion {
 304                     invalid_attr(attr, &Meta::Path(path))
 305                         .help(
 306                             "multipart suggestions use one or more `#[suggestion_part]`s rather \
 307                             than one `#[primary_span]`",
 308                         )
 309                         .emit();
 310                 } else {
 311                     report_error_if_not_applied_to_span(attr, &info)?;
 312
 313                     let binding = info.binding.binding.clone();
 314                     // FIXME(#100717): support `Option<Span>` on `primary_span` like in the
 315                     // diagnostic derive
 316                     self.span_field.set_once(binding, span);
 317                 }
 318
 319                 Ok(quote! {})
 320             }
 321             "suggestion_part" => {
 322                 self.has_suggestion_parts = true;
 323
 324                 if kind_stats.has_multipart_suggestion {
 325                     span_err(span, "`#[suggestion_part(...)]` attribute without `code = \"...\"`")
 326                         .emit();
 327                 } else {
 328                     invalid_attr(attr, &Meta::Path(path))
 329                         .help(
 330                             "`#[suggestion_part(...)]` is only valid in multipart suggestions, \
 331                              use `#[primary_span]` instead",
 332                         )
 333                         .emit();
 334                 }
 335
 336                 Ok(quote! {})
 337             }
 338             "applicability" => {
 339                 if kind_stats.has_multipart_suggestion || kind_stats.has_normal_suggestion {
 340                     report_error_if_not_applied_to_applicability(attr, &info)?;
 341
 342                     if kind_stats.all_applicabilities_static {
 343                         span_err(
 344                             span,
 345                             "`#[applicability]` has no effect if all `#[suggestion]`/\
 346                              `#[multipart_suggestion]` attributes have a static \
 347                              `applicability = \"...\"`",
 348                         )
 349                         .emit();
 350                     }
 351                     let binding = info.binding.binding.clone();
 352                     self.applicability.set_once(quote! { #binding }, span);
 353                 } else {
 354                     span_err(span, "`#[applicability]` is only valid on suggestions").emit();
 355                 }
 356
 357                 Ok(quote! {})
 358             }
 359             _ => {
 360                 let mut span_attrs = vec![];
 361                 if kind_stats.has_multipart_suggestion {
 362                     span_attrs.push("suggestion_part");
 363                 }
 364                 if !kind_stats.all_multipart_suggestions {
 365                     span_attrs.push("primary_span")
 366                 }
 367
 368                 invalid_attr(attr, &Meta::Path(path))
 369                     .help(format!(
 370                         "only `{}`, `applicability` and `skip_arg` are valid field attributes",
 371                         span_attrs.join(", ")
 372                     ))
 373                     .emit();
 374
 375                 Ok(quote! {})
 376             }
 377         }
 378     }
 379
 380     /// Generates the code for a `[Meta::List]`-like attribute on a field (e.g.
 381     /// `#[suggestion_part(code = "...")]`).
 382     fn generate_field_code_inner_list(
 383         &mut self,
 384         kind_stats: KindsStatistics,
 385         attr: &Attribute,
 386         info: FieldInfo<'_>,
 387         list: MetaList,
 388         clone_suggestion_code: bool,
 389     ) -> Result<TokenStream, DiagnosticDeriveError> {
 390         let span = attr.span().unwrap();
 391         let ident = &list.path.segments.last().unwrap().ident;
 392         let name = ident.to_string();
 393         let name = name.as_str();
 394
 395         match name {
 396             "suggestion_part" => {
 397                 if !kind_stats.has_multipart_suggestion {
 398                     throw_invalid_attr!(attr, &Meta::List(list), |diag| {
 399                         diag.help(
 400                             "`#[suggestion_part(...)]` is only valid in multipart suggestions",
 401                         )
 402                     })
 403                 }
 404
 405                 self.has_suggestion_parts = true;
 406
 407                 report_error_if_not_applied_to_span(attr, &info)?;
 408
 409                 let mut code = None;
 410                 for nested_attr in list.nested.iter() {
 411                     let NestedMeta::Meta(ref meta) = nested_attr else {
 412                         throw_invalid_nested_attr!(attr, nested_attr);
 413                     };
 414
 415                     let span = meta.span().unwrap();
 416                     let nested_name = meta.path().segments.last().unwrap().ident.to_string();
 417                     let nested_name = nested_name.as_str();
 418
 419                     match nested_name {
 420                         "code" => {
 421                             let code_field = new_code_ident();
 422                             let formatting_init = build_suggestion_code(
 423                                 &code_field,
 424                                 meta,
 425                                 self,
 426                                 AllowMultipleAlternatives::No,
 427                             );
 428                             code.set_once((code_field, formatting_init), span);
 429                         }
 430                         _ => throw_invalid_nested_attr!(attr, nested_attr, |diag| {
 431                             diag.help("`code` is the only valid nested attribute")
 432                         }),
 433                     }
 434                 }
 435
 436                 let Some((code_field, formatting_init)) = code.value() else {
 437                     span_err(span, "`#[suggestion_part(...)]` attribute without `code = \"...\"`")
 438                         .emit();
 439                     return Ok(quote! {});
 440                 };
 441                 let binding = info.binding;
 442
 443                 self.formatting_init.extend(formatting_init);
 444                 let code_field = if clone_suggestion_code {
 445                     quote! { #code_field.clone() }
 446                 } else {
 447                     quote! { #code_field }
 448                 };
 449                 Ok(quote! { suggestions.push((#binding, #code_field)); })
 450             }
 451             _ => throw_invalid_attr!(attr, &Meta::List(list), |diag| {
 452                 let mut span_attrs = vec![];
 453                 if kind_stats.has_multipart_suggestion {
 454                     span_attrs.push("suggestion_part");
 455                 }
 456                 if !kind_stats.all_multipart_suggestions {
 457                     span_attrs.push("primary_span")
 458                 }
 459                 diag.help(format!(
 460                     "only `{}`, `applicability` and `skip_arg` are valid field attributes",
 461                     span_attrs.join(", ")
 462                 ))
 463             }),
 464         }
 465     }
 466
 467     pub fn into_tokens(&mut self) -> Result<TokenStream, DiagnosticDeriveError> {
 468         let kind_slugs = self.identify_kind()?;
 469         if kind_slugs.is_empty() {
 470             if self.is_enum {
 471                 // It's okay for a variant to not be a subdiagnostic at all..
 472                 return Ok(quote! {});
 473             } else {
 474                 // ..but structs should always be _something_.
 475                 throw_span_err!(
 476                     self.variant.ast().ident.span().unwrap(),
 477                     "subdiagnostic kind not specified"
 478                 );
 479             }
 480         };
 481
 482         let kind_stats: KindsStatistics = kind_slugs.iter().map(|(kind, _slug)| kind).collect();
 483
 484         let init = if kind_stats.has_multipart_suggestion {
 485             quote! { let mut suggestions = Vec::new(); }
 486         } else {
 487             quote! {}
 488         };
 489
 490         let attr_args: TokenStream = self
 491             .variant
 492             .bindings()
 493             .iter()
 494             .filter(|binding| !binding.ast().attrs.is_empty())
 495             .map(|binding| self.generate_field_attr_code(binding, kind_stats))
 496             .collect();
 497
 498         let span_field = self.span_field.value_ref();
 499
 500         let diag = &self.parent.diag;
 501         let f = &self.parent.f;
 502         let mut calls = TokenStream::new();
 503         for (kind, slug) in kind_slugs {
 504             let message = format_ident!("__message");
 505             calls.extend(quote! { let #message = #f(#diag, rustc_errors::fluent::#slug.into()); });
 506
 507             let name = format_ident!("{}{}", if span_field.is_some() { "span_" } else { "" }, kind);
 508             let call = match kind {
 509                 SubdiagnosticKind::Suggestion {
 510                     suggestion_kind,
 511                     applicability,
 512                     code_init,
 513                     code_field,
 514                 } => {
 515                     self.formatting_init.extend(code_init);
 516
 517                     let applicability = applicability
 518                         .value()
 519                         .map(|a| quote! { #a })
 520                         .or_else(|| self.applicability.take().value())
 521                         .unwrap_or_else(|| quote! { rustc_errors::Applicability::Unspecified });
 522
 523                     if let Some(span) = span_field {
 524                         let style = suggestion_kind.to_suggestion_style();
 525                         quote! { #diag.#name(#span, #message, #code_field, #applicability, #style); }
 526                     } else {
 527                         span_err(self.span, "suggestion without `#[primary_span]` field").emit();
 528                         quote! { unreachable!(); }
 529                     }
 530                 }
 531                 SubdiagnosticKind::MultipartSuggestion { suggestion_kind, applicability } => {
 532                     let applicability = applicability
 533                         .value()
 534                         .map(|a| quote! { #a })
 535                         .or_else(|| self.applicability.take().value())
 536                         .unwrap_or_else(|| quote! { rustc_errors::Applicability::Unspecified });
 537
 538                     if !self.has_suggestion_parts {
 539                         span_err(
 540                             self.span,
 541                             "multipart suggestion without any `#[suggestion_part(...)]` fields",
 542                         )
 543                         .emit();
 544                     }
 545
 546                     let style = suggestion_kind.to_suggestion_style();
 547
 548                     quote! { #diag.#name(#message, suggestions, #applicability, #style); }
 549                 }
 550                 SubdiagnosticKind::Label => {
 551                     if let Some(span) = span_field {
 552                         quote! { #diag.#name(#span, #message); }
 553                     } else {
 554                         span_err(self.span, "label without `#[primary_span]` field").emit();
 555                         quote! { unreachable!(); }
 556                     }
 557                 }
 558                 _ => {
 559                     if let Some(span) = span_field {
 560                         quote! { #diag.#name(#span, #message); }
 561                     } else {
 562                         quote! { #diag.#name(#message); }
 563                     }
 564                 }
 565             };
 566
 567             calls.extend(call);
 568         }
 569
 570         let plain_args: TokenStream = self
 571             .variant
 572             .bindings()
 573             .iter()
 574             .filter(|binding| binding.ast().attrs.is_empty())
 575             .map(|binding| self.generate_field_set_arg(binding))
 576             .collect();
 577
 578         let formatting_init = &self.formatting_init;
 579         Ok(quote! {
 580             #init
 581             #formatting_init
 582             #attr_args
 583             #plain_args
 584             #calls
 585         })
 586     }
 587 }