Add test verifying that changing comments recompiles dependents

Author: yaahc

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -436,7 +436,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 assert!(
                     last_pos <= position,
                     "make sure that the calls to `lazy*` \
-                     are in the same order as the metadata fields",
+                    are in the same order as the metadata fields",
                 );
                 position.get() - last_pos.get()
             }
@@ -1711,7 +1711,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
             record_array!(self.tables.module_children_non_reexports[def_id] <-
                 module_children.iter().filter(|child| child.reexport_chain.is_empty())
-                    .map(|child| child.res.def_id().index));
+                .map(|child| child.res.def_id().index));
 
             record_defaulted_array!(self.tables.module_children_reexports[def_id] <-
                 module_children.iter().filter(|child| !child.reexport_chain.is_empty()));
@@ -1760,7 +1760,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             if matches!(rpitit_info, ty::ImplTraitInTraitData::Trait { .. }) {
                 record_array!(
                     self.tables.assumed_wf_types_for_rpitit[def_id]
-                        <- self.tcx.assumed_wf_types_for_rpitit(def_id)
+                    <- self.tcx.assumed_wf_types_for_rpitit(def_id)
                 );
                 self.encode_precise_capturing_args(def_id);
             }
@@ -1843,7 +1843,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             for &local_def_id in tcx.mir_keys(()) {
                 if let DefKind::AssocFn | DefKind::Fn = tcx.def_kind(local_def_id) {
                     record_array!(self.tables.deduced_param_attrs[local_def_id.to_def_id()] <-
-                        self.tcx.deduced_param_attrs(local_def_id.to_def_id()));
+                                self.tcx.deduced_param_attrs(local_def_id.to_def_id()));
                 }
             }
         }

tests/run-make/rdr-ignores-comments/after.rs

@@ -0,0 +1,8 @@
+#![crate_name = "foo"]
+#![crate_type = "lib"]
+// bbb
+pub struct Foo;
+
+impl Foo {
+    pub fn bar(self: Foo) {}
+}

tests/run-make/rdr-ignores-comments/before.rs

@@ -0,0 +1,8 @@
+#![crate_name = "foo"]
+#![crate_type = "lib"]
+// aaa
+pub struct Foo;
+
+impl Foo {
+    pub fn bar(self: Foo) {}
+}

tests/run-make/rdr-ignores-comments/rmake.rs

@@ -0,0 +1,25 @@
+// tests that we can reuse an existing rlib instead of rebuilding
+// when changin a non-doc comments in a file
+use run_make_support::{rfs, rustc};
+use std::path::Path;
+use std::hash::{Hash, Hasher};
+
+fn main() {
+    let before = check_and_hash("before.rs");
+    let after = check_and_hash("after.rs");
+    dbg!(before, after);
+    assert_eq!(before, after);
+}
+
+fn check_and_hash<P>(filename: P) -> u64
+where
+    P: AsRef<Path>,
+{
+    rfs::rename(filename, "foo.rs");
+    rustc().input("foo.rs").emit("metadata").run();
+    // hash the output
+    let bytes = rfs::read("libfoo.rmeta");
+    let mut hasher = std::hash::DefaultHasher::new();
+    bytes.hash(&mut hasher);
+    hasher.finish()
+}