tests: added extra parens compile test

gcc/testsuite/rust/compile/issue-4148.rs

@@ -0,0 +1,26 @@
+// { dg-excess-errors "warnings" }
+
+// TODO: all `xfail` conditions should be changed to `target` once the ICE in #4148 is resolved
+
+pub fn ret_parens(x: i32) -> i32 {
+    // { dg-warning "unnecessary parentheses around block return value" "#4148" { xfail *-*-* } .+1 }
+    ((x+1))
+}
+
+// { dg-warning "unnecessary parentheses around type" "#4148" { xfail *-*-* } .+1 }
+// { dg-warning "unnecessary parentheses around pattern" "#4148" { xfail *-*-* } .+1 }
+pub fn arg_ret_parens((x): (i32)) -> (i32) {
+    // { dg-warning "unnecessary parentheses around block return value" "#4148" { xfail *-*-* } .+1 }
+    ((x+1))
+}
+
+// { dg-warning "unnecessary parentheses around type" "#4148" { xfail *-*-* } .+1 }
+pub fn ret_rpit_parens2(x: i32) -> (i32) {
+    // { dg-warning "unnecessary parentheses around block return value" "#4148" { xfail *-*-* } .+1 }
+    ((x+1))
+}
+
+pub fn ret_parens3(x: i32) -> i32 {
+    // { dg-warning "unnecessary parentheses around block return value" "#4148" { xfail *-*-* } .+1 }
+    ((x+1))
+}