Add a callback that allows compiler consumers to override queries.

src/librustc_driver/lib.rs

@@ -181,6 +181,7 @@ pub fn run_compiler(
             crate_name: None,
             lint_caps: Default::default(),
             register_lints: None,
+            override_queries: None,
         };
         callbacks.config(&mut config);
         config
@@ -259,6 +260,7 @@ pub fn run_compiler(
         crate_name: None,
         lint_caps: Default::default(),
         register_lints: None,
+        override_queries: None,
     };
 
     callbacks.config(&mut config);

src/librustc_interface/interface.rs

@@ -12,6 +12,7 @@
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
 use rustc_parse::new_parser_from_source_str;
+use rustc::ty;
 use std::path::PathBuf;
 use std::result;
 use std::sync::{Arc, Mutex};
@@ -38,6 +39,8 @@ pub struct Compiler {
     pub(crate) queries: Queries,
     pub(crate) crate_name: Option<String>,
     pub(crate) register_lints: Option<Box<dyn Fn(&Session, &mut lint::LintStore) + Send + Sync>>,
+    pub(crate) override_queries:
+        Option<fn(&Session, &mut ty::query::Providers<'_>, &mut ty::query::Providers<'_>)>,
 }
 
 impl Compiler {
@@ -131,6 +134,13 @@ pub struct Config {
     /// Note that if you find a Some here you probably want to call that function in the new
     /// function being registered.
     pub register_lints: Option<Box<dyn Fn(&Session, &mut lint::LintStore) + Send + Sync>>,
+
+    /// This is a callback from the driver that is called just after we have populated
+    /// the list of queries.
+    ///
+    /// The second parameter is local providers and the third parameter is external providers.
+    pub override_queries:
+        Option<fn(&Session, &mut ty::query::Providers<'_>, &mut ty::query::Providers<'_>)>,
 }
 
 pub fn run_compiler_in_existing_thread_pool<F, R>(config: Config, f: F) -> R
@@ -157,6 +167,7 @@ pub fn run_compiler_in_existing_thread_pool<F, R>(config: Config, f: F) -> R
         queries: Default::default(),
         crate_name: config.crate_name,
         register_lints: config.register_lints,
+        override_queries: config.override_queries,
     };
 
     let _sess_abort_error = OnDrop(|| {

src/librustc_interface/passes.rs

@@ -786,6 +786,7 @@ pub fn create_global_ctxt(
     let codegen_backend = compiler.codegen_backend().clone();
     let crate_name = crate_name.to_string();
     let defs = mem::take(&mut resolver_outputs.definitions);
+    let override_queries = compiler.override_queries;
 
     let ((), result) = BoxedGlobalCtxt::new(static move || {
         let sess = &*sess;
@@ -810,6 +811,10 @@ pub fn create_global_ctxt(
         default_provide_extern(&mut extern_providers);
         codegen_backend.provide_extern(&mut extern_providers);
 
+        if let Some(callback) = override_queries {
+            callback(sess, &mut local_providers, &mut extern_providers);
+        }
+
         let gcx = TyCtxt::create_global_ctxt(
             sess,
             lint_store,

src/librustdoc/core.rs

@@ -335,6 +335,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
         crate_name,
         lint_caps,
         register_lints: None,
+        override_queries: None,
     };
 
     interface::run_compiler_in_existing_thread_pool(config, |compiler| {

src/librustdoc/test.rs

@@ -79,6 +79,7 @@ pub fn run(options: Options) -> i32 {
         crate_name: options.crate_name.clone(),
         lint_caps: Default::default(),
         register_lints: None,
+        override_queries: None,
     };
 
     let mut test_args = options.test_args.clone();

src/test/run-make-fulldeps/issue-19371/foo.rs

@@ -60,6 +60,7 @@ fn compile(code: String, output: PathBuf, sysroot: PathBuf) {
         crate_name: None,
         lint_caps: Default::default(),
         register_lints: None,
+        override_queries: None,
     };
 
     interface::run_compiler(config, |compiler| {