Rollup merge of rust-lang#62848 - matklad:xid-unicode, r=petrochenkov

Use unicode-xid crate instead of libcore

This PR proposes to remove `char::is_xid_start` and `char::is_xid_continue` functions from `libcore` and use `unicode_xid` crate from crates.io (note that this crate is already present in rust-lang/rust's Cargo.lock).

Reasons to do this:

* removing rustc-binary-specific stuff from libcore
* making sure that, across the ecosystem, there's a single definition of what rust identifier is (`unicode-xid` has almost 10 million downs, as a `proc_macro2` dependency)
* making it easier to share `rustc_lexer` crate with rust-analyzer: no need to `#[cfg]` if we are building as a part of the compiler

Reasons not to do this:

* increased maintenance burden: we'll need to upgrade unicode version both in libcore and in unicode-xid. However, this shouldn't be a too heavy burden: just running `./unicode.py` after new unicode version. I (@matklad) am ready to be a t-compiler side maintainer of unicode-xid. Moreover, given that xid-unicode is an important dependency of syn, *someone* needs to maintain it anyway.
* xid-unicode implementation is significantly slower. It uses a more compact table with binary search, instead of a trie. However, this shouldn't matter in practice, because we have fast-path for ascii anyway, and code size savings is a plus. Moreover, in rust-lang#59706 not using libcore turned out to be *faster*, presumably beacause checking for whitespace with match is even faster.

<details>

<summary>old description</summary>

Followup to rust-lang#59706

r? @eddyb

Note that this doesn't actually remove tables from libcore, to avoid conflict with rust-lang#62641.

cc unicode-rs/unicode-xid#11

</details>

Cargo.lock

@@ -1011,6 +1011,7 @@ dependencies = [
 name = "fmt_macros"
 version = "0.0.0"
 dependencies = [
+ "rustc_lexer",
  "syntax_pos",
 ]
 
@@ -2372,7 +2373,7 @@ version = "0.4.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf3d2011ab5c909338f7887f4fc896d35932e29146c12c8d01da6b22a80ba759"
 dependencies = [
- "unicode-xid",
+ "unicode-xid 0.1.0",
 ]
 
 [[package]]
@@ -3290,7 +3291,7 @@ dependencies = [
 name = "rustc_lexer"
 version = "0.1.0"
 dependencies = [
- "unicode-xid",
+ "unicode-xid 0.2.0",
 ]
 
 [[package]]
@@ -3368,6 +3369,7 @@ dependencies = [
  "rustc_apfloat",
  "rustc_data_structures",
  "rustc_errors",
+ "rustc_lexer",
  "rustc_target",
  "serialize",
  "smallvec",
@@ -3976,7 +3978,7 @@ checksum = "641e117d55514d6d918490e47102f7e08d096fdde360247e4a10f7a91a8478d3"
 dependencies = [
  "proc-macro2",
  "quote",
- "unicode-xid",
+ "unicode-xid 0.1.0",
 ]
 
 [[package]]
@@ -3988,7 +3990,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "syn",
- "unicode-xid",
+ "unicode-xid 0.1.0",
 ]
 
 [[package]]
@@ -4017,6 +4019,7 @@ dependencies = [
  "log",
  "rustc_data_structures",
  "rustc_errors",
+ "rustc_lexer",
  "rustc_target",
  "smallvec",
  "syntax",
@@ -4532,6 +4535,12 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fc72304796d0818e357ead4e000d19c9c174ab23dc11093ac919054d20a6a7fc"
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
+
 [[package]]
 name = "unicode_categories"
 version = "0.1.1"

src/libcore/char/methods.rs

@@ -547,29 +547,6 @@ impl char {
         }
     }
 
-    /// Returns `true` if this `char` satisfies the `XID_Start` Unicode property, and false
-    /// otherwise.
-    ///
-    /// `XID_Start` is a Unicode Derived Property specified in
-    /// [UAX #31](http://unicode.org/reports/tr31/#NFKC_Modifications),
-    /// mostly similar to `ID_Start` but modified for closure under `NFKx`.
-    #[unstable(feature = "unicode_internals", issue = "0")]
-    pub fn is_xid_start(self) -> bool {
-        derived_property::XID_Start(self)
-    }
-
-    /// Returns `true` if this `char` satisfies the `XID_Continue` Unicode property, and false
-    /// otherwise.
-    ///
-    /// `XID_Continue` is a Unicode Derived Property specified in
-    /// [UAX #31](http://unicode.org/reports/tr31/#NFKC_Modifications),
-    /// mostly similar to `ID_Continue` but modified for closure under NFKx.
-    #[unstable(feature = "unicode_internals", issue = "0")]
-    #[inline]
-    pub fn is_xid_continue(self) -> bool {
-        derived_property::XID_Continue(self)
-    }
-
     /// Returns `true` if this `char` is lowercase.
     ///
     /// 'Lowercase' is defined according to the terms of the Unicode Derived Core

src/libcore/unicode/mod.rs

@@ -13,8 +13,3 @@ pub mod derived_property {
 pub mod conversions {
     pub use crate::unicode::tables::conversions::{to_lower, to_upper};
 }
-
-// For use in libsyntax
-pub mod property {
-    pub use crate::unicode::tables::property::Pattern_White_Space;
-}

src/libcore/unicode/unicode.py

@@ -728,7 +728,7 @@ def generate_property_module(mod, grouped_categories, category_subset):
 
     yield "pub(crate) mod %s {\n" % mod
     for cat in sorted(category_subset):
-        if cat in ("Cc", "White_Space", "Pattern_White_Space"):
+        if cat in ("Cc", "White_Space"):
             generator = generate_small_bool_trie("%s_table" % cat, grouped_categories[cat])
         else:
             generator = generate_bool_trie("%s_table" % cat, grouped_categories[cat])
@@ -841,19 +841,18 @@ def main():
     unicode_data = load_unicode_data(get_path(UnicodeFiles.UNICODE_DATA))
     load_special_casing(get_path(UnicodeFiles.SPECIAL_CASING), unicode_data)
 
-    want_derived = {"XID_Start", "XID_Continue", "Alphabetic", "Lowercase", "Uppercase",
+    want_derived = {"Alphabetic", "Lowercase", "Uppercase",
                     "Cased", "Case_Ignorable", "Grapheme_Extend"}
     derived = load_properties(get_path(UnicodeFiles.DERIVED_CORE_PROPERTIES), want_derived)
 
     props = load_properties(get_path(UnicodeFiles.PROPS),
-                            {"White_Space", "Join_Control", "Noncharacter_Code_Point",
-                             "Pattern_White_Space"})
+                            {"White_Space", "Join_Control", "Noncharacter_Code_Point"})
 
     # Category tables
     for (name, categories, category_subset) in (
             ("general_category", unicode_data.general_categories, ["N", "Cc"]),
             ("derived_property", derived, want_derived),
-            ("property", props, ["White_Space", "Pattern_White_Space"])
+            ("property", props, ["White_Space"])
     ):
         for fragment in generate_property_module(name, categories, category_subset):
             buf.write(fragment)

src/libfmt_macros/Cargo.toml

@@ -10,4 +10,4 @@ path = "lib.rs"
 
 [dependencies]
 syntax_pos = { path = "../libsyntax_pos" }
-
+rustc_lexer = { path = "../librustc_lexer" }

src/libfmt_macros/lib.rs

@@ -597,12 +597,11 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parses a word starting at the current position. A word is considered to
-    /// be an alphabetic character followed by any number of alphanumeric
-    /// characters.
+    /// Parses a word starting at the current position. A word is the same as
+    /// Rust identifier, except that it can't start with `_` character.
     fn word(&mut self) -> &'a str {
         let start = match self.cur.peek() {
-            Some(&(pos, c)) if c.is_xid_start() => {
+            Some(&(pos, c)) if c != '_' && rustc_lexer::is_id_start(c) => {
                 self.cur.next();
                 pos
             }
@@ -611,7 +610,7 @@ impl<'a> Parser<'a> {
             }
         };
         while let Some(&(pos, c)) = self.cur.peek() {
-            if c.is_xid_continue() {
+            if rustc_lexer::is_id_continue(c) {
                 self.cur.next();
             } else {
                 return &self.input[start..pos];

src/librustc_lexer/Cargo.toml

@@ -4,12 +4,12 @@ name = "rustc_lexer"
 version = "0.1.0"
 edition = "2018"
 
-# Note that this crate purposefully does not depend on other rustc crates
-[dependencies]
-unicode-xid = { version = "0.1.0", optional = true }
-
 # Note: do not remove this blank `[lib]` section.
 # This will be used when publishing this crate as `rustc-ap-rustc_lexer`.
 [lib]
 doctest = false
 name = "rustc_lexer"
+
+# Note that this crate purposefully does not depend on other rustc crates
+[dependencies]
+unicode-xid = "0.2.0"