compiler/rustc_macros/src/query.rs

   1 use proc_macro::TokenStream;
   2 use proc_macro2::{Delimiter, TokenTree};
   3 use quote::quote;
   4 use syn::parse::{Parse, ParseStream, Result};
   5 use syn::punctuated::Punctuated;
   6 use syn::spanned::Spanned;
   7 use syn::{
   8     braced, parenthesized, parse_macro_input, AttrStyle, Attribute, Block, Error, Expr, Ident,
   9     ReturnType, Token, Type,
  10 };
  11
  12 mod kw {
  13     syn::custom_keyword!(query);
  14 }
  15
  16 /// Ident or a wildcard `_`.
  17 struct IdentOrWild(Ident);
  18
  19 impl Parse for IdentOrWild {
  20     fn parse(input: ParseStream<'_>) -> Result<Self> {
  21         Ok(if input.peek(Token![_]) {
  22             let underscore = input.parse::<Token![_]>()?;
  23             IdentOrWild(Ident::new("_", underscore.span()))
  24         } else {
  25             IdentOrWild(input.parse()?)
  26         })
  27     }
  28 }
  29
  30 /// A modifier for a query
  31 enum QueryModifier {
  32     /// The description of the query.
  33     Desc(Option<Ident>, Punctuated<Expr, Token![,]>),
  34
  35     /// Use this type for the in-memory cache.
  36     Storage(Type),
  37
  38     /// Cache the query to disk if the `Expr` returns true.
  39     Cache(Option<(IdentOrWild, IdentOrWild)>, Block),
  40
  41     /// Custom code to load the query from disk.
  42     LoadCached(Ident, Ident, Block),
  43
  44     /// A cycle error for this query aborting the compilation with a fatal error.
  45     FatalCycle,
  46
  47     /// A cycle error results in a delay_bug call
  48     CycleDelayBug,
  49
  50     /// Don't hash the result, instead just mark a query red if it runs
  51     NoHash,
  52
  53     /// Generate a dep node based on the dependencies of the query
  54     Anon,
  55
  56     /// Always evaluate the query, ignoring its dependencies
  57     EvalAlways,
  58 }
  59
  60 impl Parse for QueryModifier {
  61     fn parse(input: ParseStream<'_>) -> Result<Self> {
  62         let modifier: Ident = input.parse()?;
  63         if modifier == "desc" {
  64             // Parse a description modifier like:
  65             // `desc { |tcx| "foo {}", tcx.item_path(key) }`
  66             let attr_content;
  67             braced!(attr_content in input);
  68             let tcx = if attr_content.peek(Token![|]) {
  69                 attr_content.parse::<Token![|]>()?;
  70                 let tcx = attr_content.parse()?;
  71                 attr_content.parse::<Token![|]>()?;
  72                 Some(tcx)
  73             } else {
  74                 None
  75             };
  76             let desc = attr_content.parse_terminated(Expr::parse)?;
  77             Ok(QueryModifier::Desc(tcx, desc))
  78         } else if modifier == "cache_on_disk_if" {
  79             // Parse a cache modifier like:
  80             // `cache(tcx, value) { |tcx| key.is_local() }`
  81             let has_args = if let TokenTree::Group(group) = input.fork().parse()? {
  82                 group.delimiter() == Delimiter::Parenthesis
  83             } else {
  84                 false
  85             };
  86             let args = if has_args {
  87                 let args;
  88                 parenthesized!(args in input);
  89                 let tcx = args.parse()?;
  90                 args.parse::<Token![,]>()?;
  91                 let value = args.parse()?;
  92                 Some((tcx, value))
  93             } else {
  94                 None
  95             };
  96             let block = input.parse()?;
  97             Ok(QueryModifier::Cache(args, block))
  98         } else if modifier == "load_cached" {
  99             // Parse a load_cached modifier like:
 100             // `load_cached(tcx, id) { tcx.queries.on_disk_cache.try_load_query_result(tcx, id) }`
 101             let args;
 102             parenthesized!(args in input);
 103             let tcx = args.parse()?;
 104             args.parse::<Token![,]>()?;
 105             let id = args.parse()?;
 106             let block = input.parse()?;
 107             Ok(QueryModifier::LoadCached(tcx, id, block))
 108         } else if modifier == "storage" {
 109             let args;
 110             parenthesized!(args in input);
 111             let ty = args.parse()?;
 112             Ok(QueryModifier::Storage(ty))
 113         } else if modifier == "fatal_cycle" {
 114             Ok(QueryModifier::FatalCycle)
 115         } else if modifier == "cycle_delay_bug" {
 116             Ok(QueryModifier::CycleDelayBug)
 117         } else if modifier == "no_hash" {
 118             Ok(QueryModifier::NoHash)
 119         } else if modifier == "anon" {
 120             Ok(QueryModifier::Anon)
 121         } else if modifier == "eval_always" {
 122             Ok(QueryModifier::EvalAlways)
 123         } else {
 124             Err(Error::new(modifier.span(), "unknown query modifier"))
 125         }
 126     }
 127 }
 128
 129 /// Ensures only doc comment attributes are used
 130 fn check_attributes(attrs: Vec<Attribute>) -> Result<Vec<Attribute>> {
 131     let inner = |attr: Attribute| {
 132         if !attr.path.is_ident("doc") {
 133             Err(Error::new(attr.span(), "attributes not supported on queries"))
 134         } else if attr.style != AttrStyle::Outer {
 135             Err(Error::new(
 136                 attr.span(),
 137                 "attributes must be outer attributes (`///`), not inner attributes",
 138             ))
 139         } else {
 140             Ok(attr)
 141         }
 142     };
 143     attrs.into_iter().map(inner).collect()
 144 }
 145
 146 /// A compiler query. `query ... { ... }`
 147 struct Query {
 148     doc_comments: Vec<Attribute>,
 149     modifiers: List<QueryModifier>,
 150     name: Ident,
 151     key: IdentOrWild,
 152     arg: Type,
 153     result: ReturnType,
 154 }
 155
 156 impl Parse for Query {
 157     fn parse(input: ParseStream<'_>) -> Result<Self> {
 158         let doc_comments = check_attributes(input.call(Attribute::parse_outer)?)?;
 159
 160         // Parse the query declaration. Like `query type_of(key: DefId) -> Ty<'tcx>`
 161         input.parse::<kw::query>()?;
 162         let name: Ident = input.parse()?;
 163         let arg_content;
 164         parenthesized!(arg_content in input);
 165         let key = arg_content.parse()?;
 166         arg_content.parse::<Token![:]>()?;
 167         let arg = arg_content.parse()?;
 168         let result = input.parse()?;
 169
 170         // Parse the query modifiers
 171         let content;
 172         braced!(content in input);
 173         let modifiers = content.parse()?;
 174
 175         Ok(Query { doc_comments, modifiers, name, key, arg, result })
 176     }
 177 }
 178
 179 /// A type used to greedily parse another type until the input is empty.
 180 struct List<T>(Vec<T>);
 181
 182 impl<T: Parse> Parse for List<T> {
 183     fn parse(input: ParseStream<'_>) -> Result<Self> {
 184         let mut list = Vec::new();
 185         while !input.is_empty() {
 186             list.push(input.parse()?);
 187         }
 188         Ok(List(list))
 189     }
 190 }
 191
 192 /// A named group containing queries.
 193 ///
 194 /// For now, the name is not used any more, but the capability remains interesting for future
 195 /// developments of the query system.
 196 struct Group {
 197     #[allow(unused)]
 198     name: Ident,
 199     queries: List<Query>,
 200 }
 201
 202 impl Parse for Group {
 203     fn parse(input: ParseStream<'_>) -> Result<Self> {
 204         let name: Ident = input.parse()?;
 205         let content;
 206         braced!(content in input);
 207         Ok(Group { name, queries: content.parse()? })
 208     }
 209 }
 210
 211 struct QueryModifiers {
 212     /// The description of the query.
 213     desc: (Option<Ident>, Punctuated<Expr, Token![,]>),
 214
 215     /// Use this type for the in-memory cache.
 216     storage: Option<Type>,
 217
 218     /// Cache the query to disk if the `Block` returns true.
 219     cache: Option<(Option<(IdentOrWild, IdentOrWild)>, Block)>,
 220
 221     /// Custom code to load the query from disk.
 222     load_cached: Option<(Ident, Ident, Block)>,
 223
 224     /// A cycle error for this query aborting the compilation with a fatal error.
 225     fatal_cycle: bool,
 226
 227     /// A cycle error results in a delay_bug call
 228     cycle_delay_bug: bool,
 229
 230     /// Don't hash the result, instead just mark a query red if it runs
 231     no_hash: bool,
 232
 233     /// Generate a dep node based on the dependencies of the query
 234     anon: bool,
 235
 236     // Always evaluate the query, ignoring its dependencies
 237     eval_always: bool,
 238 }
 239
 240 /// Process query modifiers into a struct, erroring on duplicates
 241 fn process_modifiers(query: &mut Query) -> QueryModifiers {
 242     let mut load_cached = None;
 243     let mut storage = None;
 244     let mut cache = None;
 245     let mut desc = None;
 246     let mut fatal_cycle = false;
 247     let mut cycle_delay_bug = false;
 248     let mut no_hash = false;
 249     let mut anon = false;
 250     let mut eval_always = false;
 251     for modifier in query.modifiers.0.drain(..) {
 252         match modifier {
 253             QueryModifier::LoadCached(tcx, id, block) => {
 254                 if load_cached.is_some() {
 255                     panic!("duplicate modifier `load_cached` for query `{}`", query.name);
 256                 }
 257                 load_cached = Some((tcx, id, block));
 258             }
 259             QueryModifier::Storage(ty) => {
 260                 if storage.is_some() {
 261                     panic!("duplicate modifier `storage` for query `{}`", query.name);
 262                 }
 263                 storage = Some(ty);
 264             }
 265             QueryModifier::Cache(args, expr) => {
 266                 if cache.is_some() {
 267                     panic!("duplicate modifier `cache` for query `{}`", query.name);
 268                 }
 269                 cache = Some((args, expr));
 270             }
 271             QueryModifier::Desc(tcx, list) => {
 272                 if desc.is_some() {
 273                     panic!("duplicate modifier `desc` for query `{}`", query.name);
 274                 }
 275                 desc = Some((tcx, list));
 276             }
 277             QueryModifier::FatalCycle => {
 278                 if fatal_cycle {
 279                     panic!("duplicate modifier `fatal_cycle` for query `{}`", query.name);
 280                 }
 281                 fatal_cycle = true;
 282             }
 283             QueryModifier::CycleDelayBug => {
 284                 if cycle_delay_bug {
 285                     panic!("duplicate modifier `cycle_delay_bug` for query `{}`", query.name);
 286                 }
 287                 cycle_delay_bug = true;
 288             }
 289             QueryModifier::NoHash => {
 290                 if no_hash {
 291                     panic!("duplicate modifier `no_hash` for query `{}`", query.name);
 292                 }
 293                 no_hash = true;
 294             }
 295             QueryModifier::Anon => {
 296                 if anon {
 297                     panic!("duplicate modifier `anon` for query `{}`", query.name);
 298                 }
 299                 anon = true;
 300             }
 301             QueryModifier::EvalAlways => {
 302                 if eval_always {
 303                     panic!("duplicate modifier `eval_always` for query `{}`", query.name);
 304                 }
 305                 eval_always = true;
 306             }
 307         }
 308     }
 309     let desc = desc.unwrap_or_else(|| {
 310         panic!("no description provided for query `{}`", query.name);
 311     });
 312     QueryModifiers {
 313         load_cached,
 314         storage,
 315         cache,
 316         desc,
 317         fatal_cycle,
 318         cycle_delay_bug,
 319         no_hash,
 320         anon,
 321         eval_always,
 322     }
 323 }
 324
 325 /// Add the impl of QueryDescription for the query to `impls` if one is requested
 326 fn add_query_description_impl(
 327     query: &Query,
 328     modifiers: QueryModifiers,
 329     impls: &mut proc_macro2::TokenStream,
 330 ) {
 331     let name = &query.name;
 332     let arg = &query.arg;
 333     let key = &query.key.0;
 334
 335     // Find out if we should cache the query on disk
 336     let cache = if let Some((args, expr)) = modifiers.cache.as_ref() {
 337         let try_load_from_disk = if let Some((tcx, id, block)) = modifiers.load_cached.as_ref() {
 338             // Use custom code to load the query from disk
 339             quote! {
 340                 #[inline]
 341                 fn try_load_from_disk(
 342                     #tcx: TyCtxt<'tcx>,
 343                     #id: SerializedDepNodeIndex
 344                 ) -> Option<Self::Value> {
 345                     #block
 346                 }
 347             }
 348         } else {
 349             // Use the default code to load the query from disk
 350             quote! {
 351                 #[inline]
 352                 fn try_load_from_disk(
 353                     tcx: TyCtxt<'tcx>,
 354                     id: SerializedDepNodeIndex
 355                 ) -> Option<Self::Value> {
 356                     tcx.queries.on_disk_cache.as_ref().and_then(|c| c.try_load_query_result(tcx, id))
 357                 }
 358             }
 359         };
 360
 361         let tcx = args
 362             .as_ref()
 363             .map(|t| {
 364                 let t = &(t.0).0;
 365                 quote! { #t }
 366             })
 367             .unwrap_or(quote! { _ });
 368         let value = args
 369             .as_ref()
 370             .map(|t| {
 371                 let t = &(t.1).0;
 372                 quote! { #t }
 373             })
 374             .unwrap_or(quote! { _ });
 375         // expr is a `Block`, meaning that `{ #expr }` gets expanded
 376         // to `{ { stmts... } }`, which triggers the `unused_braces` lint.
 377         quote! {
 378             #[inline]
 379             #[allow(unused_variables, unused_braces)]
 380             fn cache_on_disk(
 381                 #tcx: TyCtxt<'tcx>,
 382                 #key: &Self::Key,
 383                 #value: Option<&Self::Value>
 384             ) -> bool {
 385                 #expr
 386             }
 387
 388             #try_load_from_disk
 389         }
 390     } else {
 391         if modifiers.load_cached.is_some() {
 392             panic!("load_cached modifier on query `{}` without a cache modifier", name);
 393         }
 394         quote! {}
 395     };
 396
 397     let (tcx, desc) = modifiers.desc;
 398     let tcx = tcx.as_ref().map(|t| quote! { #t }).unwrap_or(quote! { _ });
 399
 400     let desc = quote! {
 401         #[allow(unused_variables)]
 402         fn describe(
 403             #tcx: TyCtxt<'tcx>,
 404             #key: #arg,
 405         ) -> Cow<'static, str> {
 406             ::rustc_middle::ty::print::with_no_trimmed_paths(|| format!(#desc).into())
 407         }
 408     };
 409
 410     impls.extend(quote! {
 411         impl<'tcx> QueryDescription<TyCtxt<'tcx>> for queries::#name<'tcx> {
 412             #desc
 413             #cache
 414         }
 415     });
 416 }
 417
 418 pub fn rustc_queries(input: TokenStream) -> TokenStream {
 419     let groups = parse_macro_input!(input as List<Group>);
 420
 421     let mut query_stream = quote! {};
 422     let mut query_description_stream = quote! {};
 423     let mut dep_node_def_stream = quote! {};
 424     let mut cached_queries = quote! {};
 425
 426     for group in groups.0 {
 427         for mut query in group.queries.0 {
 428             let modifiers = process_modifiers(&mut query);
 429             let name = &query.name;
 430             let arg = &query.arg;
 431             let result_full = &query.result;
 432             let result = match query.result {
 433                 ReturnType::Default => quote! { -> () },
 434                 _ => quote! { #result_full },
 435             };
 436
 437             if modifiers.cache.is_some() {
 438                 cached_queries.extend(quote! {
 439                     #name,
 440                 });
 441             }
 442
 443             let mut attributes = Vec::new();
 444
 445             // Pass on the fatal_cycle modifier
 446             if modifiers.fatal_cycle {
 447                 attributes.push(quote! { fatal_cycle });
 448             };
 449             // Pass on the storage modifier
 450             if let Some(ref ty) = modifiers.storage {
 451                 attributes.push(quote! { storage(#ty) });
 452             };
 453             // Pass on the cycle_delay_bug modifier
 454             if modifiers.cycle_delay_bug {
 455                 attributes.push(quote! { cycle_delay_bug });
 456             };
 457             // Pass on the no_hash modifier
 458             if modifiers.no_hash {
 459                 attributes.push(quote! { no_hash });
 460             };
 461             // Pass on the anon modifier
 462             if modifiers.anon {
 463                 attributes.push(quote! { anon });
 464             };
 465             // Pass on the eval_always modifier
 466             if modifiers.eval_always {
 467                 attributes.push(quote! { eval_always });
 468             };
 469
 470             let attribute_stream = quote! {#(#attributes),*};
 471             let doc_comments = query.doc_comments.iter();
 472             // Add the query to the group
 473             query_stream.extend(quote! {
 474                 #(#doc_comments)*
 475                 [#attribute_stream] fn #name(#arg) #result,
 476             });
 477
 478             // Create a dep node for the query
 479             dep_node_def_stream.extend(quote! {
 480                 [#attribute_stream] #name(#arg),
 481             });
 482
 483             add_query_description_impl(&query, modifiers, &mut query_description_stream);
 484         }
 485     }
 486
 487     TokenStream::from(quote! {
 488         macro_rules! rustc_query_append {
 489             ([$($macro:tt)*][$($other:tt)*]) => {
 490                 $($macro)* {
 491                     $($other)*
 492
 493                     #query_stream
 494
 495                 }
 496             }
 497         }
 498         macro_rules! rustc_dep_node_append {
 499             ([$($macro:tt)*][$($other:tt)*]) => {
 500                 $($macro)*(
 501                     $($other)*
 502
 503                     #dep_node_def_stream
 504                 );
 505             }
 506         }
 507         macro_rules! rustc_cached_queries {
 508             ($($macro:tt)*) => {
 509                 $($macro)*(#cached_queries);
 510             }
 511         }
 512
 513         #query_description_stream
 514     })
 515 }