Add test for trimming with tabs (rust-lang#78438)

src/test/ui/terminal-width/tabs-trimming.rs

@@ -0,0 +1,13 @@
+// Test for #78438: ensure underline alignment with many tabs on the left, long line on the right
+
+// ignore-tidy-linelength
+// ignore-tidy-tab
+
+					fn main() {
+						let money = 42i32;
+						match money {
+							v @ 1 | 2 | 3 => panic!("You gave me too little money {}", v), // Long text here: TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT
+							//~^ ERROR variable `v` is not bound in all patterns
+							v => println!("Enough money {}", v),
+						}
+					}

src/test/ui/terminal-width/tabs-trimming.stderr

@@ -0,0 +1,12 @@
+error[E0408]: variable `v` is not bound in all patterns
+  --> $DIR/tabs-trimming.rs:9:16
+   |
+LL | ...   v @ 1 | 2 | 3 => panic!("You gave me too little money {}", v), // Long text here: TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT...
+   |       -       ^   ^ pattern doesn't bind `v`
+   |       |       |
+   |       |       pattern doesn't bind `v`
+   |       variable not in all patterns
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0408`.