Add mir-opt pattern type tests

Author: oli-obk

tests/mir-opt/pattern_types.main.PreCodegen.after.mir

@@ -0,0 +1,15 @@
+// MIR for `main` after PreCodegen
+
+fn main() -> () {
+    let mut _0: ();
+    scope 1 {
+        debug x => const {transmute(0x00000002): (u32) is 1..=};
+        scope 2 {
+            debug y => const {transmute(0x00000000): (u32) is 1..=};
+        }
+    }
+
+    bb0: {
+        return;
+    }
+}

tests/mir-opt/pattern_types.rs

@@ -0,0 +1,12 @@
+#![feature(pattern_types)]
+#![feature(pattern_type_macro)]
+
+use std::pat::pattern_type;
+
+// EMIT_MIR pattern_types.main.PreCodegen.after.mir
+fn main() {
+    // CHECK: debug x => const {transmute(0x00000002): (u32) is 1..=}
+    let x: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(2) };
+    // CHECK: debug y => const {transmute(0x00000000): (u32) is 1..=}
+    let y: pattern_type!(u32 is 1..) = unsafe { std::mem::transmute(0) };
+}