add crashes tests for overlapping spans

tests/crashes/146261.rs

@@ -0,0 +1,13 @@
+// This is part of series of regression tests for some diagnostics ICEs encountered in the wild with
+// suggestions having overlapping parts under https://github.com/rust-lang/rust/pull/146121.
+
+//@ needs-rustc-debug-assertions
+//@ known-bug: #146261
+
+enum U {
+    B(),
+}
+
+fn main() {
+    A(U::C)
+}

tests/crashes/146706.rs

@@ -0,0 +1,15 @@
+// This is part of series of regression tests for some diagnostics ICEs encountered in the wild with
+// suggestions having overlapping parts under https://github.com/rust-lang/rust/pull/146121.
+
+//@ needs-rustc-debug-assertions
+//@ known-bug: #146706
+
+type Alias<'a, T> = Foo<T>;
+
+enum Foo<T> {
+    Bar { t: T },
+}
+
+fn main() {
+    Alias::Bar::<u32> { t: 0 };
+}

tests/crashes/147973.rs

@@ -0,0 +1,14 @@
+// This is part of series of regression tests for some diagnostics ICEs encountered in the wild with
+// suggestions having overlapping parts under https://github.com/rust-lang/rust/pull/146121.
+// This is one MCVE from the beta crater run regressions from issue 147973.
+
+//@ needs-rustc-debug-assertions
+//@ known-bug: #147973
+
+//@ aux-build: overlapping_spans_helper.rs
+extern crate overlapping_spans_helper;
+
+fn main() {
+    let _name = Some(1);
+    overlapping_spans_helper::do_loop!(_name);
+}

tests/crashes/auxiliary/overlapping_spans_helper.rs

@@ -0,0 +1,15 @@
+// Auxiliary lib for the issue 147973 regression test with ICEs due to overlapping spans.
+
+#[macro_export]
+macro_rules! identity {
+    ($x:ident) => {
+        $x
+    };
+}
+
+#[macro_export]
+macro_rules! do_loop {
+    ($x:ident) => {
+        for $crate::identity!($x) in $x {}
+    };
+}