Add tests for newly introduced syntax

Also add some (regression) tests for discovered parser oddities

src/test/compile-fail/placement-expr-unsafe.rs

@@ -17,8 +17,8 @@ fn main() {
     use std::boxed::HEAP;
 
     let p: *const i32 = &42;
-    let _ = in HEAP { *p }; //~ ERROR requires unsafe
+    let _ = HEAP <- *p; //~ ERROR requires unsafe
 
     let p: *const _ = &HEAP;
-    let _ = in *p { 42 }; //~ ERROR requires unsafe
+    let _ = *p <- 42; //~ ERROR requires unsafe
 }

src/test/compile-fail/placement-expr-unstable.rs

@@ -18,7 +18,7 @@ extern crate core;
 fn main() {
     use std::boxed::HEAP; //~ ERROR use of unstable library feature
 
-    let _ = in HEAP { //~ ERROR use of unstable library feature
+    let _ = HEAP <- { //~ ERROR use of unstable library feature
         ::core::raw::Slice { //~ ERROR use of unstable library feature
             data: &42, //~ ERROR use of unstable library feature
             len: 1 //~ ERROR use of unstable library feature

src/test/parse-fail/assoc-oddities-1.rs

@@ -0,0 +1,22 @@
+// Copyright 2015 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.
+
+// compile-flags: -Z parse-only
+
+fn that_odd_parse() {
+    // following lines below parse and must not fail
+    x = if c { a } else { b }();
+    x <- if c { a } else { b }[n];
+    x = if true { 1 } else { 0 } as *mut _;
+    // however this does not parse and probably should fail to retain compat?
+    // NB: `..` here is arbitrary, failure happens/should happen ∀ops that aren’t `=` or `<-`
+    // see assoc-oddities-2 and assoc-oddities-3
+    ..if c { a } else { b }[n]; //~ ERROR expected one of
+}

src/test/parse-fail/assoc-oddities-2.rs

@@ -0,0 +1,16 @@
+// Copyright 2015 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.
+
+// compile-flags: -Z parse-only
+
+fn that_odd_parse() {
+    // see assoc-oddities-1 for explanation
+    x..if c { a } else { b }[n]; //~ ERROR expected one of
+}

src/test/parse-fail/assoc-oddities-3.rs

@@ -0,0 +1,16 @@
+// Copyright 2015 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.
+
+// compile-flags: -Z parse-only
+
+fn that_odd_parse() {
+    // see assoc-oddities-1 for explanation
+    x + if c { a } else { b }[n]; //~ ERROR expected one of
+}