Add test for incorrect macro span replacement

Author: estebank

tests/ui/span/macro-span-caller-replacement.rs

@@ -0,0 +1,16 @@
+macro_rules! macro_with_format { () => {
+    fn check_5(arg : usize) -> String {
+        let s : &str;
+        if arg < 5 {
+            s = format!("{arg}");
+        } else {
+            s = String::new(); //~ ERROR mismatched types
+        }
+        String::from(s)
+    }
+}}
+
+fn main() {
+    macro_with_format!(); //~ ERROR mismatched types
+    println!( "{}", check_5(6) ); 
+}

tests/ui/span/macro-span-caller-replacement.stderr

@@ -0,0 +1,29 @@
+error[E0308]: mismatched types
+  --> $DIR/macro-span-caller-replacement.rs:5:17
+   |
+LL |     macro_with_format!();
+   |     ^^^^^^^^^^^^^^^^^^^^ expected `&str`, found `String`
+   |
+   = note: this error originates in the macro `format` which comes from the expansion of the macro `macro_with_format` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0308]: mismatched types
+  --> $DIR/macro-span-caller-replacement.rs:7:17
+   |
+LL |         let s : &str;
+   |                 ---- expected due to this type
+...
+LL |             s = String::new();
+   |                 ^^^^^^^^^^^^^ expected `&str`, found `String`
+...
+LL |     macro_with_format!();
+   |     -------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `macro_with_format` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider borrowing here
+   |
+LL |             s = &String::new();
+   |                 +
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.