compiletest: Test --pretty expanded

After testing `--pretty normal`, it tries to run `--pretty expanded` and
typecheck output.
Here we don't check convergence since it really diverges: for every
iteration, some extra lines (e.g.`extern crate std`) are inserted.

Some tests are `ignore-pretty`-ed since they cause various issues
with `--pretty expanded`.

src/test/run-fail/run-unexported-tests.rs

@@ -11,6 +11,7 @@
 // error-pattern:runned an unexported test
 // compile-flags:--test
 // check-stdout
+// ignore-pretty: does not work well with `--test`
 
 mod m {
     pub fn exported() { }

src/test/run-fail/test-fail.rs

@@ -11,6 +11,7 @@
 // check-stdout
 // error-pattern:task 'test_foo' failed at
 // compile-flags: --test
+// ignore-pretty: does not work well with `--test`
 
 #[test]
 fn test_foo() {

src/test/run-fail/test-tasks-invalid-value.rs

@@ -14,6 +14,7 @@
 // error-pattern:should be a positive integer
 // compile-flags: --test
 // exec-env:RUST_TEST_TASKS=foo
+// ignore-pretty: does not work well with `--test`
 
 #[test]
 fn do_nothing() {}

src/test/run-pass-fulldeps/quote-unused-sp-no-warning.rs

@@ -9,6 +9,8 @@
 // except according to those terms.
 
 // ignore-android
+// ignore-pretty: does not work well with `--test`
+
 #![feature(quote)]
 #![deny(unused_variable)]
 

src/test/run-pass/hygienic-labels-in-let.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-pretty: pprust doesn't print hygiene output
+
 #![feature(macro_rules)]
 
 macro_rules! loop_x {

src/test/run-pass/ifmt.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-pretty: `--pretty expand` creates unnecessary `unsafe` block
 
 #![feature(macro_rules, managed_boxes)]
 #![deny(warnings)]

src/test/run-pass/shebang.rs

@@ -9,6 +9,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// pp-exact
+// ignore-pretty: `expand` addes some preludes before shebang
 
 pub fn main() { println!("Hello World"); }

src/test/run-pass/test-ignore-cfg.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // compile-flags: --test --cfg ignorecfg
+// ignore-pretty: does not work well with `--test`
 
 #[test]
 #[ignore(cfg(ignorecfg))]

src/test/run-pass/test-runner-hides-main.rs

@@ -10,6 +10,7 @@
 
 // compile-flags:--test
 // ignore-win32 #10872
+// ignore-pretty: does not work well with `--test`
 
 // Building as a test runner means that a synthetic main will be run,
 // not ours