diff --git a/src/test/ui/consts/issue-63952.rs b/src/test/ui/consts/issue-63952.rs
new file mode 100644
index 0000000000000..35cbc7003f095
--- /dev/null
+++ b/src/test/ui/consts/issue-63952.rs
@@ -0,0 +1,28 @@
+// Regression test for #63952, shouldn't hang.
+
+use std::usize;
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+struct SliceRepr {
+    ptr: *const u8,
+    len: usize,
+}
+
+union SliceTransmute {
+    repr: SliceRepr,
+    slice: &'static [u8],
+}
+
+// bad slice: length too big to even exist anywhere
+const SLICE_WAY_TOO_LONG: &[u8] = unsafe { //~ ERROR: it is undefined behavior to use this value
+    SliceTransmute {
+        repr: SliceRepr {
+            ptr: &42,
+            len: usize::MAX,
+        },
+    }
+    .slice
+};
+
+fn main() {}
diff --git a/src/test/ui/consts/issue-63952.stderr b/src/test/ui/consts/issue-63952.stderr
new file mode 100644
index 0000000000000..d5ed970fc3533
--- /dev/null
+++ b/src/test/ui/consts/issue-63952.stderr
@@ -0,0 +1,17 @@
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/issue-63952.rs:18:1
+   |
+LL | / const SLICE_WAY_TOO_LONG: &[u8] = unsafe {
+LL | |     SliceTransmute {
+LL | |         repr: SliceRepr {
+LL | |             ptr: &42,
+...  |
+LL | |     .slice
+LL | | };
+   | |__^ invalid slice: total size is bigger than largest supported object
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0080`.
diff --git a/src/test/ui/generic-associated-types/issue-68653.rs b/src/test/ui/generic-associated-types/issue-68653.rs
new file mode 100644
index 0000000000000..01f4c95639d19
--- /dev/null
+++ b/src/test/ui/generic-associated-types/issue-68653.rs
@@ -0,0 +1,16 @@
+// A regression test for #68653, which was fixed by #68938.
+
+// check-pass
+
+#![allow(incomplete_features)]
+#![feature(generic_associated_types)]
+
+trait Fun {
+    type F<'a: 'a>;
+}
+
+impl <T> Fun for T {
+    type F<'a> = Self;
+}
+
+fn main() {}
diff --git a/src/test/ui/issues/auxiliary/issue-51798.rs b/src/test/ui/issues/auxiliary/issue-51798.rs
new file mode 100644
index 0000000000000..fef5213db9f7a
--- /dev/null
+++ b/src/test/ui/issues/auxiliary/issue-51798.rs
@@ -0,0 +1,3 @@
+#![crate_type = "lib"]
+
+pub fn vec() -> Vec<u8> { vec![] }
diff --git a/src/test/ui/issues/issue-51798.rs b/src/test/ui/issues/issue-51798.rs
new file mode 100644
index 0000000000000..b075809e93ac2
--- /dev/null
+++ b/src/test/ui/issues/issue-51798.rs
@@ -0,0 +1,14 @@
+// edition:2018
+// aux-build:issue-51798.rs
+// check-pass
+
+extern crate issue_51798;
+
+mod server {
+    fn f() {
+        let mut v = issue_51798::vec();
+        v.clear();
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/parser/issue-62894.rs b/src/test/ui/parser/issue-62894.rs
new file mode 100644
index 0000000000000..b9c0bf834ddb2
--- /dev/null
+++ b/src/test/ui/parser/issue-62894.rs
@@ -0,0 +1,7 @@
+// Regression test for #62894, shouldn't crash.
+// error-pattern: this file contains an unclosed delimiter
+// error-pattern: expected one of `(`, `[`, or `{`, found keyword `fn`
+
+fn f() { assert_eq!(f(), (), assert_eq!(assert_eq!
+
+fn main() {}
diff --git a/src/test/ui/parser/issue-62894.stderr b/src/test/ui/parser/issue-62894.stderr
new file mode 100644
index 0000000000000..6db380f7a7fe2
--- /dev/null
+++ b/src/test/ui/parser/issue-62894.stderr
@@ -0,0 +1,47 @@
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-62894.rs:7:14
+   |
+LL | fn f() { assert_eq!(f(), (), assert_eq!(assert_eq!
+   |        -           -                   - unclosed delimiter
+   |        |           |
+   |        |           unclosed delimiter
+   |        unclosed delimiter
+LL | 
+LL | fn main() {}
+   |              ^
+
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-62894.rs:7:14
+   |
+LL | fn f() { assert_eq!(f(), (), assert_eq!(assert_eq!
+   |        -           -                   - unclosed delimiter
+   |        |           |
+   |        |           unclosed delimiter
+   |        unclosed delimiter
+LL | 
+LL | fn main() {}
+   |              ^
+
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-62894.rs:7:14
+   |
+LL | fn f() { assert_eq!(f(), (), assert_eq!(assert_eq!
+   |        -           -                   - unclosed delimiter
+   |        |           |
+   |        |           unclosed delimiter
+   |        unclosed delimiter
+LL | 
+LL | fn main() {}
+   |              ^
+
+error: expected one of `(`, `[`, or `{`, found keyword `fn`
+  --> $DIR/issue-62894.rs:7:1
+   |
+LL | fn f() { assert_eq!(f(), (), assert_eq!(assert_eq!
+   |                                                   - expected one of `(`, `[`, or `{`
+LL | 
+LL | fn main() {}
+   | ^^ unexpected token
+
+error: aborting due to 4 previous errors
+
diff --git a/src/test/ui/specialization/issue-39618.rs b/src/test/ui/specialization/issue-39618.rs
new file mode 100644
index 0000000000000..20e81e4359bac
--- /dev/null
+++ b/src/test/ui/specialization/issue-39618.rs
@@ -0,0 +1,27 @@
+// Regression test for #39618, shouldn't crash.
+// FIXME(JohnTitor): Centril pointed out this looks suspicions, we should revisit here.
+// More context: https://github.com/rust-lang/rust/pull/69192#discussion_r379846796
+
+// check-pass
+
+#![feature(specialization)]
+
+trait Foo {
+    fn foo(&self);
+}
+
+trait Bar {
+    fn bar(&self);
+}
+
+impl<T> Bar for T where T: Foo {
+    fn bar(&self) {}
+}
+
+impl<T> Foo for T where T: Bar {
+    fn foo(&self) {}
+}
+
+impl Foo for u64 {}
+
+fn main() {}