Drop const fn from places where it was previously added in 0.24

It makes the MSRV overly restrictive, and doesn't provide much benefit.
Also add an MSRV check to the CI

closes tafia#479

Author: dralley

.github/workflows/rust.yml

@@ -10,6 +10,13 @@ jobs:
     - name: Check fmt
       run: cargo fmt -- --check
 
+  msrv:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: dtolnay/[email protected]
+    - run: cargo check
+
   test:
     strategy:
       matrix:

Cargo.toml

@@ -10,13 +10,14 @@ repository = "https://github.com/tafia/quick-xml"
 keywords = ["xml", "serde", "parser", "writer", "html"]
 categories = ["asynchronous", "encoding", "parsing", "parser-implementations"]
 license = "MIT"
+rust-version = "1.43.1"
 
 [dependencies]
 document-features = { version = "0.2", optional = true }
 encoding_rs = { version = "0.8", optional = true }
-serde = { version = "1.0", optional = true }
-tokio = { version = "1.21", optional = true, default-features = false, features = ["io-util"] }
-memchr = "2.5"
+serde = { version = "1.0.100", optional = true }
+tokio = { version = "1.0", optional = true, default-features = false, features = ["io-util"] }
+memchr = "2.0"
 
 [dev-dependencies]
 criterion = "0.4"

Changelog.md

@@ -16,6 +16,11 @@
 
 ### Misc Changes
 
+- [#481]: Removed the uses of `const fn` added in version 0.24 in favor of a lower minimum
+  supported Rust version (1.43.1).  Minimum supported Rust version is now verified in the CI.
+
+[#481]: https://github.com/tafia/quick-xml/pull/481
+
 ## 0.25.0 -- 2022-09-10
 
 ### Bug Fixes

README.md

@@ -4,6 +4,7 @@
 [![Crate](https://img.shields.io/crates/v/quick-xml.svg)](https://crates.io/crates/quick-xml)
 [![docs.rs](https://docs.rs/quick-xml/badge.svg)](https://docs.rs/quick-xml)
 [![codecov](https://img.shields.io/codecov/c/github/tafia/quick-xml)](https://codecov.io/gh/tafia/quick-xml)
+[![MSRV](https://img.shields.io/badge/rustc-1.43.1+-ab6000.svg)](https://blog.rust-lang.org/2020/05/07/Rust.1.43.1.html)
 
 High performance xml pull reader/writer.
 

src/de/escape.rs

@@ -25,7 +25,7 @@ pub struct EscapedDeserializer<'a> {
 }
 
 impl<'a> EscapedDeserializer<'a> {
-    pub const fn new(escaped_value: Cow<'a, [u8]>, decoder: Decoder, escaped: bool) -> Self {
+    pub fn new(escaped_value: Cow<'a, [u8]>, decoder: Decoder, escaped: bool) -> Self {
         EscapedDeserializer {
             decoder,
             escaped_value,

src/de/simple_type.rs

@@ -546,7 +546,7 @@ impl<'de, 'a> SimpleTypeDeserializer<'de, 'a> {
 
     /// Constructor for tests
     #[inline]
-    const fn new(content: CowRef<'de, 'a>, escaped: bool, decoder: Decoder) -> Self {
+    fn new(content: CowRef<'de, 'a>, escaped: bool, decoder: Decoder) -> Self {
         Self {
             content,
             escaped,

src/encoding.rs

@@ -61,7 +61,7 @@ impl Decoder {
     ///
     /// [`decode`]: Self::decode
     #[cfg(feature = "encoding")]
-    pub const fn encoding(&self) -> &'static Encoding {
+    pub fn encoding(&self) -> &'static Encoding {
         self.encoding
     }
 

src/escapei.rs

@@ -203,7 +203,7 @@ where
 }
 
 #[cfg(not(feature = "escape-html"))]
-const fn named_entity(name: &str) -> Option<&str> {
+fn named_entity(name: &str) -> Option<&str> {
     // match over strings are not allowed in const functions
     let s = match name.as_bytes() {
         b"lt" => "<",
@@ -216,7 +216,7 @@ const fn named_entity(name: &str) -> Option<&str> {
     Some(s)
 }
 #[cfg(feature = "escape-html")]
-const fn named_entity(name: &str) -> Option<&str> {
+fn named_entity(name: &str) -> Option<&str> {
     // imported from https://dev.w3.org/html5/html-author/charref
     // match over strings are not allowed in const functions
     //TODO: automate up-to-dating using https://html.spec.whatwg.org/entities.json

src/events/attributes.rs

@@ -191,20 +191,20 @@ pub struct Attributes<'a> {
 impl<'a> Attributes<'a> {
     /// Internal constructor, used by `BytesStart`. Supplies data in reader's encoding
     #[inline]
-    pub(crate) const fn wrap(buf: &'a [u8], pos: usize, html: bool) -> Self {
+    pub(crate) fn wrap(buf: &'a [u8], pos: usize, html: bool) -> Self {
         Self {
             bytes: buf,
             state: IterState::new(pos, html),
         }
     }
 
     /// Creates a new attribute iterator from a buffer.
-    pub const fn new(buf: &'a str, pos: usize) -> Self {
+    pub fn new(buf: &'a str, pos: usize) -> Self {
         Self::wrap(buf.as_bytes(), pos, false)
     }
 
     /// Creates a new attribute iterator from a buffer, allowing HTML attribute syntax.
-    pub const fn html(buf: &'a str, pos: usize) -> Self {
+    pub fn html(buf: &'a str, pos: usize) -> Self {
         Self::wrap(buf.as_bytes(), pos, true)
     }
 
@@ -412,7 +412,7 @@ impl<T> Attr<T> {
 impl<'a> Attr<&'a [u8]> {
     /// Returns the key value
     #[inline]
-    pub const fn key(&self) -> QName<'a> {
+    pub fn key(&self) -> QName<'a> {
         QName(match self {
             Attr::DoubleQ(key, _) => key,
             Attr::SingleQ(key, _) => key,
@@ -425,7 +425,7 @@ impl<'a> Attr<&'a [u8]> {
     ///
     /// [HTML specification]: https://www.w3.org/TR/2012/WD-html-markup-20120329/syntax.html#syntax-attr-empty
     #[inline]
-    pub const fn value(&self) -> &'a [u8] {
+    pub fn value(&self) -> &'a [u8] {
         match self {
             Attr::DoubleQ(_, value) => value,
             Attr::SingleQ(_, value) => value,
@@ -514,7 +514,7 @@ pub(crate) struct IterState {
 }
 
 impl IterState {
-    pub const fn new(offset: usize, html: bool) -> Self {
+    pub fn new(offset: usize, html: bool) -> Self {
         Self {
             state: State::Next(offset),
             html,

src/events/mod.rs

@@ -72,7 +72,7 @@ pub struct BytesStart<'a> {
 impl<'a> BytesStart<'a> {
     /// Internal constructor, used by `Reader`. Supplies data in reader's encoding
     #[inline]
-    pub(crate) const fn wrap(content: &'a [u8], name_len: usize) -> Self {
+    pub(crate) fn wrap(content: &'a [u8], name_len: usize) -> Self {
         BytesStart {
             buf: Cow::Borrowed(content),
             name_len,
@@ -344,7 +344,7 @@ impl<'a> BytesDecl<'a> {
     }
 
     /// Creates a `BytesDecl` from a `BytesStart`
-    pub const fn from_start(start: BytesStart<'a>) -> Self {
+    pub fn from_start(start: BytesStart<'a>) -> Self {
         Self { content: start }
     }
 
@@ -549,7 +549,7 @@ pub struct BytesEnd<'a> {
 impl<'a> BytesEnd<'a> {
     /// Internal constructor, used by `Reader`. Supplies data in reader's encoding
     #[inline]
-    pub(crate) const fn wrap(name: Cow<'a, [u8]>) -> Self {
+    pub(crate) fn wrap(name: Cow<'a, [u8]>) -> Self {
         BytesEnd { name }
     }
 

src/name.rs

@@ -21,7 +21,7 @@ pub struct QName<'a>(pub &'a [u8]);
 impl<'a> QName<'a> {
     /// Converts this name to an internal slice representation.
     #[inline(always)]
-    pub const fn into_inner(self) -> &'a [u8] {
+    pub fn into_inner(self) -> &'a [u8] {
         self.0
     }
 
@@ -138,7 +138,7 @@ pub struct LocalName<'a>(&'a [u8]);
 impl<'a> LocalName<'a> {
     /// Converts this name to an internal slice representation.
     #[inline(always)]
-    pub const fn into_inner(self) -> &'a [u8] {
+    pub fn into_inner(self) -> &'a [u8] {
         self.0
     }
 }
@@ -188,7 +188,7 @@ pub struct Prefix<'a>(&'a [u8]);
 impl<'a> Prefix<'a> {
     /// Extracts internal slice
     #[inline(always)]
-    pub const fn into_inner(self) -> &'a [u8] {
+    pub fn into_inner(self) -> &'a [u8] {
         self.0
     }
 }
@@ -253,7 +253,7 @@ impl<'a> Namespace<'a> {
     /// [non-normalized]: https://www.w3.org/TR/REC-xml/#AVNormalize
     /// [IRI reference]: https://datatracker.ietf.org/doc/html/rfc3987
     #[inline(always)]
-    pub const fn into_inner(self) -> &'a [u8] {
+    pub fn into_inner(self) -> &'a [u8] {
         self.0
     }
     //TODO: implement value normalization and use it when comparing namespaces

src/reader/mod.rs

@@ -377,7 +377,7 @@ enum EncodingRef {
 #[cfg(feature = "encoding")]
 impl EncodingRef {
     #[inline]
-    const fn encoding(&self) -> &'static Encoding {
+    fn encoding(&self) -> &'static Encoding {
         match self {
             Self::Implicit(e) => e,
             Self::Explicit(e) => e,
@@ -386,7 +386,7 @@ impl EncodingRef {
         }
     }
     #[inline]
-    const fn can_be_refined(&self) -> bool {
+    fn can_be_refined(&self) -> bool {
         match self {
             Self::Implicit(_) | Self::BomDetected(_) => true,
             Self::Explicit(_) | Self::XmlDetected(_) => false,
@@ -531,7 +531,7 @@ impl<R> Reader<R> {
     }
 
     /// Gets a reference to the underlying reader.
-    pub const fn get_ref(&self) -> &R {
+    pub fn get_ref(&self) -> &R {
         &self.reader
     }
 
@@ -543,7 +543,7 @@ impl<R> Reader<R> {
     /// Gets the current byte position in the input data.
     ///
     /// Useful when debugging errors.
-    pub const fn buffer_position(&self) -> usize {
+    pub fn buffer_position(&self) -> usize {
         // when internal state is OpenedTag, we have actually read until '<',
         // which we don't want to show
         if let ParseState::OpenedTag = self.parser.state {
@@ -561,7 +561,7 @@ impl<R> Reader<R> {
     /// If `encoding` feature is enabled and no encoding is specified in declaration,
     /// defaults to UTF-8.
     #[inline]
-    pub const fn decoder(&self) -> Decoder {
+    pub fn decoder(&self) -> Decoder {
         self.parser.decoder()
     }
 }
@@ -848,7 +848,7 @@ impl ReadElementState {
 
 /// A function to check whether the byte is a whitespace (blank, new line, carriage return or tab)
 #[inline]
-pub(crate) const fn is_whitespace(b: u8) -> bool {
+pub(crate) fn is_whitespace(b: u8) -> bool {
     match b {
         b' ' | b'\r' | b'\n' | b'\t' => true,
         _ => false,

src/reader/parser.rs

@@ -236,7 +236,7 @@ impl Parser {
     ///
     /// If `encoding` feature is enabled and no encoding is specified in declaration,
     /// defaults to UTF-8.
-    pub const fn decoder(&self) -> Decoder {
+    pub fn decoder(&self) -> Decoder {
         Decoder {
             #[cfg(feature = "encoding")]
             encoding: self.encoding.encoding(),

src/reader/slice_reader.rs

@@ -353,7 +353,7 @@ mod test {
     use crate::reader::XmlSource;
 
     /// Default buffer constructor just pass the byte array from the test
-    const fn identity<T>(input: T) -> T {
+    fn identity<T>(input: T) -> T {
         input
     }
 

src/se/mod.rs

@@ -117,7 +117,7 @@ impl<'r, W: Write> Serializer<'r, W> {
     /// Note, that attempt to serialize a non-struct (including unit structs
     /// and newtype structs) will end up to an error. Use `with_root` to create
     /// serializer with explicitly defined root element name
-    pub const fn new(writer: W) -> Self {
+    pub fn new(writer: W) -> Self {
         Self::with_root(Writer::new(writer), None)
     }
 
@@ -169,7 +169,7 @@ impl<'r, W: Write> Serializer<'r, W> {
     ///     r#"<root question="The Ultimate Question of Life, the Universe, and Everything" answer="42"/>"#
     /// );
     /// ```
-    pub const fn with_root(writer: Writer<W>, root_tag: Option<&'r str>) -> Self {
+    pub fn with_root(writer: Writer<W>, root_tag: Option<&'r str>) -> Self {
         Self { writer, root_tag }
     }
 

src/writer.rs

@@ -61,7 +61,7 @@ pub struct Writer<W: Write> {
 
 impl<W: Write> Writer<W> {
     /// Creates a `Writer` from a generic writer.
-    pub const fn new(inner: W) -> Writer<W> {
+    pub fn new(inner: W) -> Writer<W> {
         Writer {
             writer: inner,
             indent: None,