Add structopt dependency in version 0.3.7

This patch series replaces argparse with structopt in the argument
handling code. As a first step, we need structopt as a dependency.

Import subrepo structopt/:structopt at efbdda4753592e27bc430fb01f7b9650b2f3174d
Import subrepo bitflags/:bitflags at 30668016aca6bd3b02c766e8347e0b4080d4c296
Import subrepo clap/:clap at 784524f7eb193e35f81082cc69454c8c21b948f7
Import subrepo heck/:heck at 093d56fbf001e1506e56dbfa38631d99b1066df1
Import subrepo proc-macro-error/:proc-macro-error at 6c4cfe79a622c5de8ae68557993542be46eacae2
Import subrepo proc-macro2/:proc-macro2 at d5d48eddca4566e5438e8a2cbed4a74e049544de
Import subrepo quote/:quote at 727436c6c137b20f0f34dde5d8fda2679b9747ad
Import subrepo rustversion/:rustversion at 0c5663313516263059ce9059ef81fc7a1cf655ca
Import subrepo syn-mid/:syn-mid at 5d3d85414a9e6674e1857ec22a87b96e04a6851a
Import subrepo syn/:syn at e87c27e87f6f4ef8919d0372bdb056d53ef0d8f3
Import subrepo textwrap/:textwrap at abcd618beae3f74841032aa5b53c1086b0a57ca2
Import subrepo unicode-segmentation/:unicode-segmentation at 637c9874c4fe0c205ff27787faf150a40295c6c3
Import subrepo unicode-width/:unicode-width at 3033826f8bf05e82724140a981d5941e48fce393
Import subrepo unicode-xid/:unicode-xid at 4baae9fffb156ba229665b972a9cd5991787ceb7

2 files changed, 24 insertions, 0 deletions

diff --git a/syn/examples/trace-var/example/Cargo.toml b/syn/examples/trace-var/example/Cargo.toml
new file mode 100644
index 0000000..d2ad650
--- /dev/null
+++ b/syn/examples/trace-var/example/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "example"
+version = "0.0.0"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+edition = "2018"
+publish = false
+
+[dependencies]
+trace-var = { path = "../trace-var" }
diff --git a/syn/examples/trace-var/example/src/main.rs b/syn/examples/trace-var/example/src/main.rs
new file mode 100644
index 0000000..da2c10b
--- /dev/null
+++ b/syn/examples/trace-var/example/src/main.rs
@@ -0,0 +1,15 @@
+use trace_var::trace_var;
+
+fn main() {
+    println!("{}", factorial(8));
+}
+
+#[trace_var(p, n)]
+fn factorial(mut n: u64) -> u64 {
+    let mut p = 1;
+    while n > 1 {
+        p *= n;
+        n -= 1;
+    }
+    p
+}