Change query proc macro to be more rust-analyzer friendly

compiler/rustc_macros/src/query.rs

@@ -1,4 +1,5 @@
 use proc_macro::TokenStream;
+use proc_macro2::Span;
 use quote::{quote, quote_spanned};
 use syn::parse::{Parse, ParseStream, Result};
 use syn::punctuated::Punctuated;
@@ -62,7 +63,7 @@ impl Parse for Query {
         // If there are no doc-comments, give at least some idea of what
         // it does by showing the query description.
         if doc_comments.is_empty() {
-            doc_comments.push(doc_comment_from_desc(&modifiers.desc.1)?);
+            doc_comments.push(doc_comment_from_desc(&modifiers.desc.expr_list)?);
         }
 
         Ok(Query { doc_comments, modifiers, name, key, arg, result })
@@ -82,15 +83,27 @@ impl<T: Parse> Parse for List<T> {
     }
 }
 
+struct Desc {
+    modifier: Ident,
+    tcx_binding: Option<Ident>,
+    expr_list: Punctuated<Expr, Token![,]>,
+}
+
+struct CacheOnDiskIf {
+    modifier: Ident,
+    tcx_binding: Option<Pat>,
+    block: Block,
+}
+
 struct QueryModifiers {
     /// The description of the query.
-    desc: (Option<Ident>, Punctuated<Expr, Token![,]>),
+    desc: Desc,
 
     /// Use this type for the in-memory cache.
     arena_cache: Option<Ident>,
 
     /// Cache the query to disk if the `Block` returns true.
-    cache_on_disk_if: Option<(Option<Pat>, Block)>,
+    cache_on_disk_if: Option<CacheOnDiskIf>,
 
     /// A cycle error for this query aborting the compilation with a fatal error.
     cycle_fatal: Option<Ident>,
@@ -164,23 +177,23 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
             // `desc { |tcx| "foo {}", tcx.item_path(key) }`
             let attr_content;
             braced!(attr_content in input);
-            let tcx = if attr_content.peek(Token![|]) {
+            let tcx_binding = if attr_content.peek(Token![|]) {
                 attr_content.parse::<Token![|]>()?;
                 let tcx = attr_content.parse()?;
                 attr_content.parse::<Token![|]>()?;
                 Some(tcx)
             } else {
                 None
             };
-            let list = attr_content.parse_terminated(Expr::parse, Token![,])?;
-            try_insert!(desc = (tcx, list));
+            let expr_list = attr_content.parse_terminated(Expr::parse, Token![,])?;
+            try_insert!(desc = Desc { modifier, tcx_binding, expr_list });
         } else if modifier == "cache_on_disk_if" {
             // Parse a cache-on-disk modifier like:
             //
             // `cache_on_disk_if { true }`
             // `cache_on_disk_if { key.is_local() }`
             // `cache_on_disk_if(tcx) { tcx.is_typeck_child(key.to_def_id()) }`
-            let args = if input.peek(token::Paren) {
+            let tcx_binding = if input.peek(token::Paren) {
                 let args;
                 parenthesized!(args in input);
                 let tcx = Pat::parse_single(&args)?;
@@ -189,7 +202,7 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
                 None
             };
             let block = input.parse()?;
-            try_insert!(cache_on_disk_if = (args, block));
+            try_insert!(cache_on_disk_if = CacheOnDiskIf { modifier, tcx_binding, block });
         } else if modifier == "arena_cache" {
             try_insert!(arena_cache = modifier);
         } else if modifier == "cycle_fatal" {
@@ -275,44 +288,32 @@ struct HelperTokenStreams {
 }
 
 fn make_helpers_for_query(query: &Query, streams: &mut HelperTokenStreams) {
-    let Query { name, key, modifiers, .. } = &query;
+    let Query { name, key, modifiers, arg, .. } = &query;
 
-    // This dead code exists to instruct rust-analyzer about the link between the `rustc_queries`
-    // query names and the corresponding produced provider. The issue is that by nature of this
-    // macro producing a higher order macro that has all its token in the macro declaration we lose
-    // any meaningful spans, resulting in rust-analyzer being unable to make the connection between
-    // the query name and the corresponding providers field. The trick to fix this is to have
-    // `rustc_queries` emit a field access with the given name's span which allows it to successfully
-    // show references / go to definition to the corresponding provider assignment which is usually
-    // the more interesting place.
-    let ra_hint = quote! {
-        let crate::query::Providers { #name: _, .. };
-    };
+    // Replace span for `name` to make rust-analyzer ignore it.
+    let mut erased_name = name.clone();
+    erased_name.set_span(Span::call_site());
 
     // Generate a function to check whether we should cache the query to disk, for some key.
-    if let Some((args, expr)) = modifiers.cache_on_disk_if.as_ref() {
-        let tcx = args.as_ref().map(|t| quote! { #t }).unwrap_or_else(|| quote! { _ });
-        // expr is a `Block`, meaning that `{ #expr }` gets expanded
-        // to `{ { stmts... } }`, which triggers the `unused_braces` lint.
+    if let Some(CacheOnDiskIf { tcx_binding, block, .. }) = modifiers.cache_on_disk_if.as_ref() {
+        let tcx = tcx_binding.as_ref().map(|t| quote! { #t }).unwrap_or_else(|| quote! { _ });
         // we're taking `key` by reference, but some rustc types usually prefer being passed by value
         streams.cache_on_disk_if_fns_stream.extend(quote! {
-            #[allow(unused_variables, unused_braces, rustc::pass_by_value)]
+            #[allow(unused_variables, rustc::pass_by_value)]
             #[inline]
-            pub fn #name<'tcx>(#tcx: TyCtxt<'tcx>, #key: &crate::queries::#name::Key<'tcx>) -> bool {
-                #ra_hint
-                #expr
-            }
+            pub fn #erased_name<'tcx>(#tcx: TyCtxt<'tcx>, #key: &crate::queries::#name::Key<'tcx>) -> bool
+            #block
         });
     }
 
-    let (tcx, desc) = &modifiers.desc;
-    let tcx = tcx.as_ref().map_or_else(|| quote! { _ }, |t| quote! { #t });
+    let Desc { tcx_binding, expr_list, .. } = &modifiers.desc;
+    let tcx = tcx_binding.as_ref().map_or_else(|| quote! { _ }, |t| quote! { #t });
 
     let desc = quote! {
         #[allow(unused_variables)]
-        pub fn #name<'tcx>(tcx: TyCtxt<'tcx>, key: crate::queries::#name::Key<'tcx>) -> String {
+        pub fn #erased_name<'tcx>(tcx: TyCtxt<'tcx>, key: #arg) -> String {
             let (#tcx, #key) = (tcx, key);
-            format!(#desc)
+            format!(#expr_list)
         }
     };
 
@@ -321,12 +322,88 @@ fn make_helpers_for_query(query: &Query, streams: &mut HelperTokenStreams) {
     });
 }
 
+/// Add hints for rust-analyzer
+fn add_to_analyzer_stream(query: &Query, analyzer_stream: &mut proc_macro2::TokenStream) {
+    // Add links to relevant modifiers
+
+    let modifiers = &query.modifiers;
+
+    let mut modifiers_stream = quote! {};
+
+    let name = &modifiers.desc.modifier;
+    modifiers_stream.extend(quote! {
+        crate::query::modifiers::#name;
+    });
+
+    if let Some(CacheOnDiskIf { modifier, .. }) = &modifiers.cache_on_disk_if {
+        modifiers_stream.extend(quote! {
+            crate::query::modifiers::#modifier;
+        });
+    }
+
+    macro_rules! doc_link {
+        ( $( $modifier:ident ),+ $(,)? ) => {
+            $(
+                if let Some(name) = &modifiers.$modifier {
+                    modifiers_stream.extend(quote! {
+                        crate::query::modifiers::#name;
+                    });
+                }
+            )+
+        }
+    }
+
+    doc_link!(
+        arena_cache,
+        cycle_fatal,
+        cycle_delay_bug,
+        cycle_stash,
+        no_hash,
+        anon,
+        eval_always,
+        depth_limit,
+        separate_provide_extern,
+        feedable,
+        return_result_from_ensure_ok,
+    );
+
+    let name = &query.name;
+
+    // Replace span for `name` to make rust-analyzer ignore it.
+    let mut erased_name = name.clone();
+    erased_name.set_span(Span::call_site());
+
+    let result = &query.result;
+
+    // This dead code exists to instruct rust-analyzer about the link between the `rustc_queries`
+    // query names and the corresponding produced provider. The issue is that by nature of this
+    // macro producing a higher order macro that has all its token in the macro declaration we lose
+    // any meaningful spans, resulting in rust-analyzer being unable to make the connection between
+    // the query name and the corresponding providers field. The trick to fix this is to have
+    // `rustc_queries` emit a field access with the given name's span which allows it to successfully
+    // show references / go to definition to the corresponding provider assignment which is usually
+    // the more interesting place.
+    let ra_hint = quote! {
+        let crate::query::Providers { #name: _, .. };
+    };
+
+    analyzer_stream.extend(quote! {
+        #[inline(always)]
+        fn #erased_name<'tcx>() #result {
+            #ra_hint
+            #modifiers_stream
+            loop {}
+        }
+    });
+}
+
 pub(super) fn rustc_queries(input: TokenStream) -> TokenStream {
     let queries = parse_macro_input!(input as List<Query>);
 
     let mut query_stream = quote! {};
     let mut helpers = HelperTokenStreams::default();
     let mut feedable_queries = quote! {};
+    let mut analyzer_stream = quote! {};
     let mut errors = quote! {};
 
     macro_rules! assert {
@@ -409,6 +486,7 @@ pub(super) fn rustc_queries(input: TokenStream) -> TokenStream {
             });
         }
 
+        add_to_analyzer_stream(&query, &mut analyzer_stream);
         make_helpers_for_query(&query, &mut helpers);
     }
 
@@ -442,6 +520,12 @@ pub(super) fn rustc_queries(input: TokenStream) -> TokenStream {
             }
         }
 
+        // Add hints for rust-analyzer
+        mod _analyzer_hints {
+            use super::*;
+            #analyzer_stream
+        }
+
         /// Functions that format a human-readable description of each query
         /// and its key, as specified by the `desc` query modifier.
         ///

compiler/rustc_middle/src/query/mod.rs

@@ -13,6 +13,7 @@ mod keys;
 pub mod on_disk_cache;
 #[macro_use]
 pub mod plumbing;
+pub(crate) mod modifiers;
 
 pub fn describe_as_module(def_id: impl Into<LocalDefId>, tcx: TyCtxt<'_>) -> String {
     let def_id = def_id.into();

compiler/rustc_middle/src/query/modifiers.rs

@@ -0,0 +1,77 @@
+//! This contains documentation which is linked from query modifiers used in the `rustc_queries!` proc macro.
+#![allow(unused, non_camel_case_types)]
+// FIXME: Update and clarify documentation for these modifiers.
+
+/// # `desc` query modifier
+///
+/// The description of the query. This modifier is required on every query.
+pub struct desc;
+
+/// # `arena_cache` query modifier
+///
+/// Use this type for the in-memory cache.
+pub struct arena_cache;
+
+/// # `cache_on_disk_if` query modifier
+///
+/// Cache the query to disk if the `Block` returns true.
+pub struct cache_on_disk_if;
+
+/// # `cycle_fatal` query modifier
+///
+/// A cycle error for this query aborting the compilation with a fatal error.
+pub struct cycle_fatal;
+
+/// # `cycle_delay_bug` query modifier
+///
+/// A cycle error results in a delay_bug call
+pub struct cycle_delay_bug;
+
+/// # `cycle_stash` query modifier
+///
+/// A cycle error results in a stashed cycle error that can be unstashed and canceled later
+pub struct cycle_stash;
+
+/// # `no_hash` query modifier
+///
+/// Don't hash the result, instead just mark a query red if it runs
+pub struct no_hash;
+
+/// # `anon` query modifier
+///
+/// Generate a dep node based on the dependencies of the query
+pub struct anon;
+
+/// # `eval_always` query modifier
+///
+/// Always evaluate the query, ignoring its dependencies
+pub struct eval_always;
+
+/// # `depth_limit` query modifier
+///
+/// Whether the query has a call depth limit
+pub struct depth_limit;
+
+/// # `separate_provide_extern` query modifier
+///
+/// Use a separate query provider for local and extern crates
+pub struct separate_provide_extern;
+
+/// # `feedable` query modifier
+///
+/// Generate a `feed` method to set the query's value from another query.
+pub struct feedable;
+
+/// # `return_result_from_ensure_ok` query modifier
+///
+/// When this query is called via `tcx.ensure_ok()`, it returns
+/// `Result<(), ErrorGuaranteed>` instead of `()`. If the query needs to
+/// be executed, and that execution returns an error, the error result is
+/// returned to the caller.
+///
+/// If execution is skipped, a synthetic `Ok(())` is returned, on the
+/// assumption that a query with all-green inputs must have succeeded.
+///
+/// Can only be applied to queries with a return value of
+/// `Result<_, ErrorGuaranteed>`.
+pub struct return_result_from_ensure_ok;

compiler/rustc_middle/src/query/plumbing.rs

@@ -462,10 +462,14 @@ macro_rules! define_callbacks {
         }
 
         pub struct Providers {
-            $(pub $name: for<'tcx> fn(
-                TyCtxt<'tcx>,
-                $name::LocalKey<'tcx>,
-            ) -> $name::ProvidedValue<'tcx>,)*
+            $(
+                /// This is the provider for the query. Use `Find references` on this to
+                /// navigate between the provider assignment and the query definition.
+                pub $name: for<'tcx> fn(
+                    TyCtxt<'tcx>,
+                    $name::LocalKey<'tcx>,
+                ) -> $name::ProvidedValue<'tcx>,
+            )*
         }
 
         pub struct ExternProviders {