Drop Rust 2018 compatibility

.appveyor.yml

@@ -1,11 +1,6 @@
 environment:
   matrix:
   - TOOLCHAIN: stable
-  - TOOLCHAIN: nightly
-
-matrix:
-  allow_failures:
-    - TOOLCHAIN: nightly
 
 install:
   - appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe

.travis.yml

@@ -1,7 +1,6 @@
 language: rust
 
 rust:
-  - 1.31.0 # Rust 2018
   - stable
   - nightly
 

Cargo.toml

@@ -21,16 +21,11 @@ appveyor = { repository = "mgeisler/version-sync" }
 codecov = { repository = "mgeisler/version-sync" }
 
 [dependencies]
-# This crate is compatible with Rust 2018, i.e., Rustc version 1.31.0.
-# Version requirements of dependencies can be bumped as long as the
-# dependencies compile with that compiler version. Some versions
-# requirements below an upper limit to indicate when the dependency
-# stops compiling with a Rust 2018 compatible compiler.
-pulldown-cmark = { version = "0.4, <0.5", default-features = false }
+pulldown-cmark = { version = "0.7", default-features = false }
 semver-parser = "0.9"
 syn = { version = "1.0", features = ["full"] }
 proc-macro2 = { version = "1.0", features = ["span-locations"] }
 toml = "0.5"
-url = "1.0, <2.0"
-itertools = "0.8"
+url = "2.0"
+itertools = "0.9"
 regex = "1.1"

README.md

@@ -2,7 +2,6 @@
 
 [![](https://img.shields.io/crates/v/version-sync.svg)][crates-io]
 [![](https://docs.rs/version-sync/badge.svg)][api-docs]
-[![](https://img.shields.io/badge/rustc-1.31.0-4d76ae.svg)][rust-2018]
 [![](https://travis-ci.org/mgeisler/version-sync.svg?branch=master)][travis-ci]
 [![](https://ci.appveyor.com/api/projects/status/github/mgeisler/version-sync?branch=master&svg=true)][appveyor]
 [![](https://codecov.io/gh/mgeisler/version-sync/branch/master/graph/badge.svg)][codecov]
@@ -109,6 +108,22 @@ your_crate = "0.1.2"
 
 This is a changelog describing the most important changes per release.
 
+### Unreleased
+
+Drop support for Rust 1.31.0 since our dependencies keep releasing new
+patch versions that push up the minimum required Rust version. These
+updates mean that `version-sync` 0.8.1 no longer compiles with Rust
+1.31.0 because `cargo sync` will pull in too new versions of the
+direct and transitive dependencies. This happens even if there are no
+changes in `version-sync`.
+
+The constant build failures in our CI makes it infeasible to keep
+`version-sync` compatible with any particular version of Rust. We will
+therefore track the latest stable version of Rust from now on.
+
+At the time of writing, the code compiles with Rust 1.36, but this
+will likely become outdated soon.
+
 ### Version 0.8.1 — April 3rd, 2019
 
 Dependencies were relaxed to make it easier to upgrade `version-sync`.

src/markdown_deps.rs

@@ -1,4 +1,4 @@
-use pulldown_cmark::{Event, Parser, Tag};
+use pulldown_cmark::{CodeBlockKind::Fenced, Event, Parser, Tag};
 use semver_parser::range::parse as parse_request;
 use semver_parser::range::VersionReq;
 use semver_parser::version::parse as parse_version;
@@ -63,7 +63,7 @@ fn find_toml_blocks(text: &str) -> Vec<CodeBlock<'_>> {
     let mut code_blocks = Vec::new();
     for (event, range) in parser.into_offset_iter() {
         match event {
-            Event::Start(Tag::CodeBlock(ref lang)) if is_toml_block(lang) => {
+            Event::Start(Tag::CodeBlock(Fenced(lang))) if is_toml_block(&lang) => {
                 let line_count = text[..range.start].lines().count();
                 let code_block = &text[range];
                 let start = 1 + code_block.find('\n').unwrap_or(0);

tests/version-numbers.rs

@@ -11,13 +11,6 @@ fn test_readme_changelog() {
     );
 }
 
-#[test]
-fn test_minimum_rustc_version() {
-    let version = r"1\.31\.0";
-    version_sync::assert_contains_regex!(".travis.yml", &format!(r"^  - {}", version));
-    version_sync::assert_contains_regex!("README.md", &format!("badge/rustc-{}", version));
-}
-
 #[test]
 fn test_html_root_url() {
     version_sync::assert_html_root_url_updated!("src/lib.rs");