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

5 files changed, 97 insertions, 0 deletions

diff --git a/syn-mid/examples/const_fn/Cargo.toml b/syn-mid/examples/const_fn/Cargo.toml
new file mode 100644
index 0000000..d823e76
--- /dev/null
+++ b/syn-mid/examples/const_fn/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "const_fn"
+version = "0.0.0"
+authors = ["Taiki Endo <te316e89@gmail.com>"]
+edition = "2018"
+publish = false
+
+[lib]
+proc-macro = true
+path = "lib.rs"
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = "1.0"
+syn-mid = { version = "0.4", path = "../..", features = ["clone-impls"] }
diff --git a/syn-mid/examples/const_fn/lib.rs b/syn-mid/examples/const_fn/lib.rs
new file mode 100644
index 0000000..29255f2
--- /dev/null
+++ b/syn-mid/examples/const_fn/lib.rs
@@ -0,0 +1,31 @@
+#![warn(rust_2018_idioms)]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use proc_macro2::TokenStream as TokenStream2;
+use quote::quote;
+use syn_mid::ItemFn;
+
+/// An attribute for easy generation of a const function with conditional compilations.
+#[proc_macro_attribute]
+pub fn const_fn(args: TokenStream, function: TokenStream) -> TokenStream {
+    assert!(!args.is_empty(), "requires an argument");
+
+    let mut function = syn::parse_macro_input!(function as ItemFn);
+    let mut const_function = function.clone();
+
+    if function.constness.is_some() {
+        function.constness = None;
+    } else {
+        const_function.constness = Some(Default::default());
+    }
+
+    let args = TokenStream2::from(args);
+    TokenStream::from(quote! {
+        #[cfg(not(#args))]
+        #function
+        #[cfg(#args)]
+        #const_function
+    })
+}
diff --git a/syn-mid/examples/const_fn_test/Cargo.toml b/syn-mid/examples/const_fn_test/Cargo.toml
new file mode 100644
index 0000000..b3e2807
--- /dev/null
+++ b/syn-mid/examples/const_fn_test/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "const_fn_test"
+version = "0.0.0"
+authors = ["Taiki Endo <te316e89@gmail.com>"]
+edition = "2018"
+publish = false
+
+[dependencies]
+const_fn = { path = "../const_fn" }
diff --git a/syn-mid/examples/const_fn_test/build.rs b/syn-mid/examples/const_fn_test/build.rs
new file mode 100644
index 0000000..bebf234
--- /dev/null
+++ b/syn-mid/examples/const_fn_test/build.rs
@@ -0,0 +1,16 @@
+use std::{env, process::Command};
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+
+    if is_nightly() {
+        println!("cargo:rustc-cfg=nightly");
+    }
+}
+
+fn is_nightly() -> bool {
+    env::var_os("RUSTC")
+        .and_then(|rustc| Command::new(rustc).arg("--version").output().ok())
+        .and_then(|output| String::from_utf8(output.stdout).ok())
+        .map_or(false, |version| version.contains("nightly"))
+}
diff --git a/syn-mid/examples/const_fn_test/tests/test.rs b/syn-mid/examples/const_fn_test/tests/test.rs
new file mode 100644
index 0000000..1b2c742
--- /dev/null
+++ b/syn-mid/examples/const_fn_test/tests/test.rs
@@ -0,0 +1,25 @@
+#![cfg_attr(nightly, feature(const_fn, const_vec_new))]
+#![warn(rust_2018_idioms)]
+#![allow(dead_code)]
+
+use const_fn::const_fn;
+
+#[const_fn(nightly)]
+fn const_vec_new<T>() -> Vec<T> {
+    let vec = Vec::new();
+    vec
+}
+
+#[test]
+fn test_stable() {
+    assert_eq!(const_vec_new::<u8>(), Vec::new());
+}
+
+#[cfg(nightly)]
+const CONST_UNSTABLE: Vec<u8> = const_vec_new();
+
+#[cfg(nightly)]
+#[test]
+fn test_unstable() {
+    assert_eq!(CONST_UNSTABLE, Vec::new());
+}