avoid blessing cargo deps's source code in ui tests

Cargo.lock

@@ -662,6 +662,7 @@ dependencies = [
  "diff",
  "getopts",
  "glob",
+ "home",
  "lazycell",
  "libc",
  "miow",
@@ -1597,6 +1598,15 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
+[[package]]
+name = "home"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5444c27eef6923071f7ebcc33e3444508466a76f7a2b93da00ed6e19f30c1ddb"
+dependencies = [
+ "windows-sys 0.48.0",
+]
+
 [[package]]
 name = "html-checker"
 version = "0.1.0"

src/tools/compiletest/Cargo.toml

@@ -24,6 +24,7 @@ walkdir = "2"
 glob = "0.3.0"
 lazycell = "1.3.0"
 anyhow = "1"
+home = "0.5.5"
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"

src/tools/compiletest/src/runtest.rs

@@ -2335,6 +2335,15 @@ impl<'test> TestCx<'test> {
         rustc.arg("-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX");
         rustc.arg("-Ztranslate-remapped-path-to-local-path=no");
 
+        // Hide Cargo dependency sources from ui tests to make sure the error message doesn't
+        // change depending on whether $CARGO_HOME is remapped or not. If this is not present,
+        // when $CARGO_HOME is remapped the source won't be shown, and when it's not remapped the
+        // source will be shown, causing a blessing hell.
+        rustc.arg("-Z").arg(format!(
+            "ignore-directory-in-diagnostics-source-blocks={}",
+            home::cargo_home().expect("failed to find cargo home").to_str().unwrap()
+        ));
+
         // Optionally prevent default --sysroot if specified in test compile-flags.
         if !self.props.compile_flags.iter().any(|flag| flag.starts_with("--sysroot"))
             && !self.config.host_rustcflags.iter().any(|flag| flag == "--sysroot")

tests/ui/issues/issue-21763.stderr

@@ -9,9 +9,6 @@ LL |     foo::<HashMap<Rc<()>, Rc<()>>>();
    = note: required for `hashbrown::raw::RawTable<(Rc<()>, Rc<()>)>` to implement `Send`
 note: required because it appears within the type `HashMap<Rc<()>, Rc<()>, RandomState>`
   --> $HASHBROWN_SRC_LOCATION
-   |
-LL | pub struct HashMap<K, V, S = DefaultHashBuilder, A: Allocator + Clone = Global> {
-   |            ^^^^^^^
 note: required because it appears within the type `HashMap<Rc<()>, Rc<()>>`
   --> $SRC_DIR/std/src/collections/hash/map.rs:LL:COL
 note: required by a bound in `foo`