librustc: Always parse `macro!()`/`macro![]` as expressions if not

followed by a semicolon.

This allows code like `vec![1i, 2, 3].len();` to work.

This breaks code that uses macros as statements without putting
semicolons after them, such as:

    fn main() {
        ...
        assert!(a == b)
        assert!(c == d)
        println(...);
    }

It also breaks code that uses macros as items without semicolons:

    local_data_key!(foo)

    fn main() {
        println("hello world")
    }

Add semicolons to fix this code. Those two examples can be fixed as
follows:

    fn main() {
        ...
        assert!(a == b);
        assert!(c == d);
        println(...);
    }

    local_data_key!(foo);

    fn main() {
        println("hello world")
    }

RFC #378.

Closes #18635.

[breaking-change]

1 files changed, 10 insertions, 6 deletions

diff --git a/src/libsyntax/diagnostics/plugin.rs b/src/libsyntax/diagnostics/plugin.rs
index cb2a1f8acd8..bcce5538314 100644
--- a/src/libsyntax/diagnostics/plugin.rs
+++ b/src/libsyntax/diagnostics/plugin.rs
@@ -18,12 +18,16 @@ use ext::build::AstBuilder;
 use parse::token;
 use ptr::P;
 
-thread_local!(static REGISTERED_DIAGNOSTICS: RefCell<HashMap<Name, Option<Name>>> = {
-    RefCell::new(HashMap::new())
-})
-thread_local!(static USED_DIAGNOSTICS: RefCell<HashMap<Name, Span>> = {
-    RefCell::new(HashMap::new())
-})
+thread_local! {
+    static REGISTERED_DIAGNOSTICS: RefCell<HashMap<Name, Option<Name>>> = {
+        RefCell::new(HashMap::new())
+    }
+}
+thread_local! {
+    static USED_DIAGNOSTICS: RefCell<HashMap<Name, Span>> = {
+        RefCell::new(HashMap::new())
+    }
+}
 
 fn with_registered_diagnostics<T, F>(f: F) -> T where
     F: FnOnce(&mut HashMap<Name, Option<Name>>) -> T,