rustfmt destroys json! (and other?) macro calls

[chaaz]

I use the json! macro from serde_json (https://docs.serde.rs/serde_json/macro.json.html) quite a bit, but since version 0.3.4, rustfmt has been eating everything! This is not good.

$ git log -1
commit 6714a447d063b079de8fb2884ded2c8c3e96bc1d (HEAD, tag: 0.3.4)
Author: Seiichi Uchida <[email protected]>
Date:   Sat Dec 23 12:25:42 2017 +0900

    0.3.4
$ rustup run nightly cargo install --force --path .
  Installing rustfmt-nightly v0.3.4 (file:///.../rustfmt)
   Compiling rustfmt-nightly v0.3.4 (file:///.../rustfmt)
    Finished release [optimized] target(s) in 30.76 secs
   Replacing /.../.cargo/bin/rustfmt
   Replacing /.../.cargo/bin/cargo-fmt
   Replacing /.../.cargo/bin/rustfmt-format-diff
   Replacing /.../.cargo/bin/git-fmt

$ rustup run nightly rustfmt --write-mode=diff testme.rs
Diff in /Users/charlieozinga/Documents/Projects/gits/g2c/testme.rs at line 1:
 fn main() {⏎
-  let value = json!({⏎
-    "hello": "this is text",⏎
-    "goodbye": 123.4⏎
-  });⏎
+  let value = json!({});⏎
 }⏎
 ⏎

[chaaz]

Hmm.. looks like there's already a test for this (sort of) that's failing? Maybe it's the latest rust toolchain that's the culprit?

$ rustc --version
rustc 1.25.0-nightly (ee220daca 2018-01-07)
$ cargo test
...
Mismatch at tests/target/macros.rs:213:
 ⏎
 // #1577⏎
 fn issue1577() {⏎
-    let json = json!({⏎
-        "foo": "bar",⏎
-    });⏎
+    let json =⏎
+        json!({});⏎

[nrc]

dup of #2338