Add test for hygiene caching issue

Author: Aaron1011

src/test/incremental/hygiene/auxiliary/cached_hygiene.rs

@@ -0,0 +1,37 @@
+// revisions:rpass1 rpass2
+// compile-flags: -Z query-dep-graph
+
+// We use #[inline(always)] to ensure that the downstream crate
+// will always load the MIR for these functions
+
+#![feature(rustc_attrs)]
+
+#[allow(unused)]
+macro_rules! first_macro {
+    () => {
+        println!("New call!");
+    }
+}
+
+#[rustc_dirty(label="typeck", cfg="rpass2")]
+#[inline(always)]
+pub fn changed_fn() {
+    // This will cause additional hygiene to be generate,
+    // which will cause the SyntaxContext/ExpnId raw ids to be
+    // different when we write out `my_fn` to the crate metadata.
+    #[cfg(rpass2)]
+    first_macro!();
+}
+
+macro_rules! print_loc {
+    () => {
+        println!("Caller loc: {}", std::panic::Location::caller());
+    }
+}
+
+#[rustc_clean(cfg="rpass2")]
+#[inline(always)]
+pub fn unchanged_fn() {
+    print_loc!();
+}
+

src/test/incremental/hygiene/load_cached_hygiene.rs

@@ -0,0 +1,48 @@
+// revisions:rpass1 rpass2
+// compile-flags: -Z query-dep-graph
+// aux-build:cached_hygiene.rs
+
+// This tests the folllowing scenario
+// 1. A foreign crate is compiled with incremental compilation.
+//    This causes hygiene information to be saved to the incr cache.
+// 2. One function is the foreign crate is modified. This causes the
+//    optimized mir for an unmodified function to be loaded from the
+//    incremental cache and written out to the crate metadata.
+// 3. In the process of loading and writing out this function's MIR,
+//    we load hygiene information from the incremental cache and
+//    write it to our metadata.
+// 4. This hygiene information is loaded by another crate (this file)
+
+// Previously, this situation would cause hygiene identifiers
+// (SyntaxContexts and ExpnIds) to get corrupted when we tried to
+// serialize the hygiene information loaded from the incr cache into
+// the metadata. Specifically, we were not resetting `orig_id`
+// for an `EpxnData` generate in the current crate, which would cause
+// us to serialize the `ExpnId` pointing to a garbage location in
+// the metadata.
+
+#![feature(rustc_attrs)]
+
+#![rustc_partition_reused(module="load_cached_hygiene-call_unchanged_function", cfg="rpass2")]
+#![rustc_partition_codegened(module="load_cached_hygiene-call_changed_function", cfg="rpass2")]
+
+
+extern crate cached_hygiene;
+
+pub mod call_unchanged_function {
+
+    pub fn unchanged() {
+        cached_hygiene::unchanged_fn();
+    }
+}
+
+pub mod call_changed_function {
+    pub fn changed() {
+        cached_hygiene::changed_fn();
+    }
+}
+
+pub fn main() {
+    call_unchanged_function::unchanged();
+    call_changed_function::changed();
+}