New error format for E0512

[rust.git] / COMPILER_TESTS.md

diff --git a/COMPILER_TESTS.md b/COMPILER_TESTS.md
index e2a957e396191150bda46f9610b0a9a44d8f9714..91975c1f9ed9a312f978dcb4478d6b2f977c4efb 100644 (file)
--- a/COMPILER_TESTS.md
+++ b/COMPILER_TESTS.md
@@ -42,3 +42,43 @@ whole, instead of just a few lines inside the test.
 * `ignore-test` always ignores the test
 * `ignore-lldb` and `ignore-gdb` will skip the debuginfo tests
 * `min-{gdb,lldb}-version`
+* `should-fail` indicates that the test should fail; used for "meta testing",
+  where we test the compiletest program itself to check that it will generate
+  errors in appropriate scenarios. This header is ignored for pretty-printer tests.
+
+## Revisions
+
+Certain classes of tests support "revisions" (as of the time of this
+writing, this includes run-pass, compile-fail, run-fail, and
+incremental, though incremental tests are somewhat
+different). Revisions allow a single test file to be used for multiple
+tests. This is done by adding a special header at the top of the file:
+
+```
+// revisions: foo bar baz
+```
+
+This will result in the test being compiled (and tested) three times,
+once with `--cfg foo`, once with `--cfg bar`, and once with `--cfg
+baz`. You can therefore use `#[cfg(foo)]` etc within the test to tweak
+each of these results.
+
+You can also customize headers and expected error messages to a particular
+revision. To do this, add `[foo]` (or `bar`, `baz`, etc) after the `//`
+comment, like so:
+
+```
+// A flag to pass in only for cfg `foo`:
+//[foo]compile-flags: -Z verbose
+
+#[cfg(foo)]
+fn test_foo() {
+    let x: usize = 32_u32; //[foo]~ ERROR mismatched types
+}
+```
+
+Note that not all headers have meaning when customized to a revision.
+For example, the `ignore-test` header (and all "ignore" headers)
+currently only apply to the test as a whole, not to particular
+revisions. The only headers that are intended to really work when
+customized to a revision are error patterns and compiler flags.