Rust: Add pattern match type inference test

Author: paldepind

rust/ql/test/library-tests/type-inference/CONSISTENCY/TypeInferenceConsistency.expected

@@ -0,0 +1,9 @@
+nonUniqueCertainType
+| pattern_matching.rs:487:9:487:18 | ref_tuple1 |  |
+| pattern_matching.rs:487:9:487:18 | ref_tuple1 |  |
+| pattern_matching.rs:488:12:488:17 | TuplePat |  |
+| pattern_matching.rs:488:21:488:30 | ref_tuple1 |  |
+| pattern_matching.rs:494:9:494:18 | ref_tuple2 |  |
+| pattern_matching.rs:494:9:494:18 | ref_tuple2 |  |
+| pattern_matching.rs:495:9:495:14 | TuplePat |  |
+| pattern_matching.rs:495:18:495:27 | ref_tuple2 |  |

rust/ql/test/library-tests/type-inference/pattern_matching.rs

@@ -482,6 +482,19 @@ pub fn tuple_patterns() {
             println!("Single element tuple: {}", single_elem);
         }
     }
+
+    // Tuple pattern on reference to tuple in `let` expression
+    let ref_tuple1: &(i32, i32) = &(1, 2);
+    if let (n, m) = ref_tuple1 {
+        println!("n: {}", n);
+        println!("m: {}", m);
+    }
+
+    // Tuple pattern on reference to tuple in `let` statement
+    let ref_tuple2: &(i32, i32) = &(1, 2);
+    let (n, m) = ref_tuple2;
+    println!("n: {}", n);
+    println!("m: {}", m);
 }
 
 pub fn parenthesized_patterns() {