Add a UI test with code that only works with homogeneous try

Author: scottmcm

tests/ui/try-block/try-block-homogeneous.rs

@@ -0,0 +1,36 @@
+//@ check-pass
+//@ edition: 2018
+
+#![feature(try_blocks)]
+#![crate_type = "lib"]
+
+// A few examples of code that only works with homogeneous `try`
+
+pub fn index_or_zero(x: &[i32], i: usize, j: usize) -> i32 {
+    // With heterogeneous `try` this fails because
+    // it tries to call a method on a type variable.
+    try { x.get(i)? + x.get(j)? }.unwrap_or(0)
+}
+
+pub fn do_nothing_on_errors(a: &str, b: &str) {
+    // With heterogeneous `try` this fails because
+    // an underscore pattern doesn't constrain the output type.
+    let _ = try {
+        let a = a.parse::<i32>()?;
+        let b = b.parse::<u32>()?;
+        println!("{a} {b}");
+    };
+}
+
+pub fn print_error_once(a: &str, b: &str) {
+    match try {
+        let a = a.parse::<i32>()?;
+        let b = b.parse::<u32>()?;
+        (a, b)
+    } {
+        Ok(_pair) => {}
+        // With heterogeneous `try` this fails because
+        // nothing constrains the error type in `e`.
+        Err(e) => eprintln!("{e}"),
+    }
+}