tests: add a revision to macro_backtrace without -Zmacro-backtrace.

Author: eddyb

src/test/ui/macro_backtrace/main.stderr renamed to src/test/ui/macro_backtrace/main.-Zmacro-backtrace.stderr

@@ -1,5 +1,5 @@
 error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `error`
-  --> $DIR/main.rs:9:20
+  --> $DIR/main.rs:10:20
    |
 LL | / macro_rules! pong {
 LL | |     () => { syntax error };
@@ -11,7 +11,7 @@ LL |       pong!();
    |       -------- in this macro invocation
 
 error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `error`
-  --> $DIR/main.rs:9:20
+  --> $DIR/main.rs:10:20
    |
 LL | / macro_rules! pong {
 LL | |     () => { syntax error };
@@ -31,7 +31,7 @@ LL |   () => { pong ! () ; }
    |   in this expansion of `ping!`
 
 error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `error`
-  --> $DIR/main.rs:9:20
+  --> $DIR/main.rs:10:20
    |
 LL | / macro_rules! pong {
 LL | |     () => { syntax error };

src/test/ui/macro_backtrace/main.default.stderr

@@ -0,0 +1,35 @@
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `error`
+  --> $DIR/main.rs:10:20
+   |
+LL |     () => { syntax error };
+   |                    ^^^^^ expected one of 8 possible tokens
+...
+LL |     pong!();
+   |     -------- in this macro invocation
+   |
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `error`
+  --> $DIR/main.rs:10:20
+   |
+LL |     () => { syntax error };
+   |                    ^^^^^ expected one of 8 possible tokens
+...
+LL |     ping!();
+   |     -------- in this macro invocation
+   |
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `error`
+  --> $DIR/main.rs:10:20
+   |
+LL |     () => { syntax error };
+   |                    ^^^^^ expected one of 8 possible tokens
+...
+LL |     deep!();
+   |     -------- in this macro invocation
+   |
+   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 3 previous errors
+

src/test/ui/macro_backtrace/main.rs

@@ -1,6 +1,7 @@
 // Test that the macro backtrace facility works
 // aux-build:ping.rs
-// compile-flags: -Z macro-backtrace
+// revisions: default -Zmacro-backtrace
+//[-Zmacro-backtrace] compile-flags: -Z macro-backtrace
 
 #[macro_use] extern crate ping;