forbid #[track_caller] on main

src/test/ui/rfc-2091-track-caller/error-with-main.rs

@@ -0,0 +1,4 @@
+#[track_caller] //~ ERROR `main` function is not allowed to be
+fn main() {
+    panic!("{}: oh no", std::panic::Location::caller());
+}

src/test/ui/rfc-2091-track-caller/error-with-main.stderr

@@ -0,0 +1,12 @@
+error: `main` function is not allowed to be `#[track_caller]`
+  --> $DIR/error-with-main.rs:1:1
+   |
+LL |   #[track_caller]
+   |   ^^^^^^^^^^^^^^^
+LL | / fn main() {
+LL | |     panic!("{}: oh no", std::panic::Location::caller());
+LL | | }
+   | |_- `main` function is not allowed to be `#[track_caller]`
+
+error: aborting due to previous error
+

src/test/ui/rfc-2091-track-caller/error-with-start.rs

@@ -0,0 +1,7 @@
+#![feature(start)]
+
+#[start]
+#[track_caller] //~ ERROR start is not allowed to be `#[track_caller]`
+fn start(_argc: isize, _argv: *const *const u8) -> isize {
+    panic!("{}: oh no", std::panic::Location::caller());
+}

src/test/ui/rfc-2091-track-caller/error-with-start.stderr

@@ -0,0 +1,12 @@
+error: start is not allowed to be `#[track_caller]`
+  --> $DIR/error-with-start.rs:4:1
+   |
+LL |   #[track_caller]
+   |   ^^^^^^^^^^^^^^^
+LL | / fn start(_argc: isize, _argv: *const *const u8) -> isize {
+LL | |     panic!("{}: oh no", std::panic::Location::caller());
+LL | | }
+   | |_- start is not allowed to be `#[track_caller]`
+
+error: aborting due to previous error
+