Permit . after macro invocations at the starts of statements

This fixes the most commonly-encountered case of #5941.

Author: ftxqxd

src/libsyntax/parse/parser.rs

@@ -2810,8 +2810,12 @@ impl<'a> Parser<'a> {
     /// actually, this seems to be the main entry point for
     /// parsing an arbitrary expression.
     pub fn parse_assign_expr(&mut self) -> P<Expr> {
-        let lo = self.span.lo;
         let lhs = self.parse_binops();
+        self.parse_more_assign_expr(lhs)
+    }
+
+    pub fn parse_more_assign_expr(&mut self, lhs: P<Expr>) -> P<Expr> {
+        let lo = self.span.lo;
         let restrictions = self.restrictions & RestrictionNoStructLiteral;
         match self.token {
           token::EQ => {
@@ -3557,8 +3561,17 @@ impl<'a> Parser<'a> {
             let hi = self.span.hi;
 
             if id.name == token::special_idents::invalid.name {
-                P(spanned(lo, hi, StmtMac(
-                    spanned(lo, hi, MacInvocTT(pth, tts, EMPTY_CTXT)), false)))
+                if self.token == token::DOT {
+                    let b = self.mk_mac_expr(lo,
+                                             hi,
+                                             MacInvocTT(pth, tts, EMPTY_CTXT));
+                    let d = self.parse_dot_or_call_expr_with(b);
+                    let e = self.parse_more_assign_expr(d);
+                    P(spanned(lo, e.span.hi, StmtExpr(e, ast::DUMMY_NODE_ID)))
+                } else {
+                    P(spanned(lo, hi, StmtMac(
+                        spanned(lo, hi, MacInvocTT(pth, tts, EMPTY_CTXT)), false)))
+                }
             } else {
                 // if it has a special ident, it's definitely an item
                 P(spanned(lo, hi, StmtDecl(

src/test/run-pass/macro-followed-by-dot.rs

@@ -0,0 +1,40 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(macro_rules, tuple_indexing)]
+
+struct Foo(bool);
+
+impl Foo {
+    fn frob(&mut self) {
+        self.0 = true;
+    }
+}
+
+impl Drop for Foo {
+    fn drop(&mut self) {
+        if !self.0 {
+            fail!("frob() was not run!")
+        }
+    }
+}
+
+macro_rules! foo {
+    ($x: ident) => {{ $x = Foo(false); $x }}
+}
+
+fn main() {
+    let mut x;
+    // This both tests that it is parsed properly AND that it actually runs the method
+    foo!(x).frob();
+    // Test that other operators can follow the macro invocation
+    let mut y;
+    foo!(y).0 = true;
+}