fix compile_fail doctests with post-mono errors

Author: RalfJung

cargo-miri/src/phases.rs

@@ -364,7 +364,7 @@ pub fn phase_rustc(mut args: impl Iterator<Item = String>, phase: RustcPhase) {
             let out_filename = out_filename.expect("rustdoc must pass `-o`");
 
             cmd.args(&args);
-            cmd.env("MIRI_BE_RUSTC", "target");
+            cmd.env("MIRI_BE_RUSTC", "rustdoc");
 
             if verbose > 0 {
                 eprintln!(

src/bin/miri.rs

@@ -123,14 +123,31 @@ impl rustc_driver::Callbacks for MiriCompilerCalls {
     }
 }
 
+#[derive(Copy, Clone, Debug, PartialEq)]
+enum MiriBeRustcMode {
+    Target,
+    Host,
+    Rustdoc,
+}
+
+impl MiriBeRustcMode {
+    fn target_crate(self) -> bool {
+        use MiriBeRustcMode::*;
+        match self {
+            Target | Rustdoc => true,
+            Host => false,
+        }
+    }
+}
+
 struct MiriBeRustCompilerCalls {
-    target_crate: bool,
+    mode: MiriBeRustcMode,
 }
 
 impl rustc_driver::Callbacks for MiriBeRustCompilerCalls {
     #[allow(rustc::potential_query_instability)] // rustc_codegen_ssa (where this code is copied from) also allows this lint
     fn config(&mut self, config: &mut Config) {
-        if config.opts.prints.is_empty() && self.target_crate {
+        if config.opts.prints.is_empty() && self.mode == MiriBeRustcMode::Target {
             // Queries overridden here affect the data stored in `rmeta` files of dependencies,
             // which will be used later in non-`MIRI_BE_RUSTC` mode.
             config.override_queries = Some(|_, local_providers| {
@@ -179,6 +196,21 @@ impl rustc_driver::Callbacks for MiriBeRustCompilerCalls {
             });
         }
     }
+
+    fn after_analysis<'tcx>(
+        &mut self,
+        _: &rustc_interface::interface::Compiler,
+        queries: &'tcx rustc_interface::Queries<'tcx>,
+    ) -> Compilation {
+        queries.global_ctxt().unwrap().enter(|tcx| {
+            // Make sure compile_fail tests with post-monomorphization const-eval errors work as
+            // intended in rustdoc mode.
+            if self.mode == MiriBeRustcMode::Rustdoc {
+                let _ = tcx.collect_and_partition_mono_items(());
+            }
+        });
+        Compilation::Continue
+    }
 }
 
 fn show_error(msg: &impl std::fmt::Display) -> ! {
@@ -351,19 +383,18 @@ fn main() {
             rustc_driver::install_ice_hook(rustc_driver::DEFAULT_BUG_REPORT_URL, |_| ());
         rustc_driver::init_rustc_env_logger(&early_dcx);
 
-        let target_crate = if crate_kind == "target" {
-            true
-        } else if crate_kind == "host" {
-            false
-        } else {
-            panic!("invalid `MIRI_BE_RUSTC` value: {crate_kind:?}")
+        let mode = match crate_kind.to_str().unwrap_or_default() {
+            "target" => MiriBeRustcMode::Target,
+            "rustdoc" => MiriBeRustcMode::Rustdoc,
+            "host" => MiriBeRustcMode::Host,
+            _ => panic!("invalid `MIRI_BE_RUSTC` value: {crate_kind:?}"),
         };
 
         // We cannot use `rustc_driver::main` as we need to adjust the CLI arguments.
         run_compiler(
             args,
-            target_crate,
-            &mut MiriBeRustCompilerCalls { target_crate },
+            mode.target_crate(),
+            &mut MiriBeRustCompilerCalls { mode },
             using_internal_features,
         )
     }

test-cargo-miri/src/lib.rs

@@ -1,13 +1,31 @@
 /// Doc-test test
+///
 /// ```rust
 /// assert!(cargo_miri_test::make_true());
 /// ```
+///
+/// `no_run` test:
+///
 /// ```rust,no_run
 /// assert!(!cargo_miri_test::make_true());
 /// ```
+///
+/// `compile_fail` test:
+///
 /// ```rust,compile_fail
 /// assert!(cargo_miri_test::make_true() == 5);
 /// ```
+///
+/// Post-monomorphization error in `compile_fail` test:
+///
+/// ```rust,compile_fail
+/// struct Fail<T>(T);
+/// impl<T> Fail<T> {
+///     const C: () = panic!();
+/// }
+///
+/// let _val = Fail::<i32>::C;
+/// ```
 #[no_mangle]
 pub fn make_true() -> bool {
     issue_1567::use_the_dependency();

test-cargo-miri/test.default.stdout.ref

@@ -10,7 +10,7 @@ running 6 tests
 test result: ok. 5 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out
 
 
-running 4 tests
-....
-test result: ok. 4 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+running 5 tests
+.....
+test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
 

test-cargo-miri/test.filter.stdout.ref

@@ -13,5 +13,5 @@ test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 5 filtered out
 
 running 0 tests
 
-test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 4 filtered out; finished in $TIME
+test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 5 filtered out; finished in $TIME