Properly account for editions in names

This PR touches a lot of parts. But the main changes are changing
`hir_expand::Name` to be raw edition-dependently and only when necessary
(unrelated to how the user originally wrote the identifier),
and changing `is_keyword()` and `is_raw_identifier()` to be edition-aware
(this was done in #17896, but the FIXMEs were fixed here).

It is possible that I missed some cases, but most IDE parts should properly
escape (or not escape) identifiers now.

The rules of thumb are:

 - If we show the identifier to the user, its rawness should be determined
   by the edition of the edited crate. This is nice for IDE features,
   but really important for changes we insert to the source code.
 - For tests, I chose `Edition::CURRENT` (so we only have to (maybe) update
   tests when an edition becomes stable, to avoid churn).
 - For debugging tools (helper methods and logs), I used `Edition::LATEST`.

crates/hir-expand/src/mod_path.rs

@@ -14,7 +14,7 @@ use crate::{
 use base_db::CrateId;
 use intern::sym;
 use smallvec::SmallVec;
-use span::SyntaxContextId;
+use span::{Edition, SyntaxContextId};
 use syntax::{ast, AstNode};
 
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -140,8 +140,12 @@ impl ModPath {
         UnescapedModPath(self)
     }
 
-    pub fn display<'a>(&'a self, db: &'a dyn crate::db::ExpandDatabase) -> impl fmt::Display + 'a {
-        Display { db, path: self }
+    pub fn display<'a>(
+        &'a self,
+        db: &'a dyn crate::db::ExpandDatabase,
+        edition: Edition,
+    ) -> impl fmt::Display + 'a {
+        Display { db, path: self, edition }
     }
 }
 
@@ -154,11 +158,12 @@ impl Extend<Name> for ModPath {
 struct Display<'a> {
     db: &'a dyn ExpandDatabase,
     path: &'a ModPath,
+    edition: Edition,
 }
 
 impl fmt::Display for Display<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        display_fmt_path(self.db, self.path, f, true)
+        display_fmt_path(self.db, self.path, f, Escape::IfNeeded(self.edition))
     }
 }
 
@@ -169,7 +174,7 @@ struct UnescapedDisplay<'a> {
 
 impl fmt::Display for UnescapedDisplay<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        display_fmt_path(self.db, self.path.0, f, false)
+        display_fmt_path(self.db, self.path.0, f, Escape::No)
     }
 }
 
@@ -178,11 +183,17 @@ impl From<Name> for ModPath {
         ModPath::from_segments(PathKind::Plain, iter::once(name))
     }
 }
+
+enum Escape {
+    No,
+    IfNeeded(Edition),
+}
+
 fn display_fmt_path(
     db: &dyn ExpandDatabase,
     path: &ModPath,
     f: &mut fmt::Formatter<'_>,
-    escaped: bool,
+    escaped: Escape,
 ) -> fmt::Result {
     let mut first_segment = true;
     let mut add_segment = |s| -> fmt::Result {
@@ -210,10 +221,9 @@ fn display_fmt_path(
             f.write_str("::")?;
         }
         first_segment = false;
-        if escaped {
-            segment.display(db).fmt(f)?;
-        } else {
-            segment.unescaped().display(db).fmt(f)?;
+        match escaped {
+            Escape::IfNeeded(edition) => segment.display(db, edition).fmt(f)?,
+            Escape::No => segment.unescaped().display(db).fmt(f)?,
         }
     }
     Ok(())
@@ -322,9 +332,11 @@ fn convert_path_tt(db: &dyn ExpandDatabase, tt: &[tt::TokenTree]) -> Option<ModP
         tt::Leaf::Ident(tt::Ident { sym: text, .. }) if *text == sym::self_ => PathKind::SELF,
         tt::Leaf::Ident(tt::Ident { sym: text, .. }) if *text == sym::super_ => {
             let mut deg = 1;
-            while let Some(tt::Leaf::Ident(tt::Ident { sym: text, span, is_raw })) = leaves.next() {
+            while let Some(tt::Leaf::Ident(tt::Ident { sym: text, span, is_raw: _ })) =
+                leaves.next()
+            {
                 if *text != sym::super_ {
-                    segments.push(Name::new_symbol_maybe_raw(text.clone(), *is_raw, span.ctx));
+                    segments.push(Name::new_symbol(text.clone(), span.ctx));
                     break;
                 }
                 deg += 1;
@@ -333,19 +345,13 @@ fn convert_path_tt(db: &dyn ExpandDatabase, tt: &[tt::TokenTree]) -> Option<ModP
         }
         tt::Leaf::Ident(tt::Ident { sym: text, .. }) if *text == sym::crate_ => PathKind::Crate,
         tt::Leaf::Ident(ident) => {
-            segments.push(Name::new_symbol_maybe_raw(
-                ident.sym.clone(),
-                ident.is_raw,
-                ident.span.ctx,
-            ));
+            segments.push(Name::new_symbol(ident.sym.clone(), ident.span.ctx));
             PathKind::Plain
         }
         _ => return None,
     };
     segments.extend(leaves.filter_map(|leaf| match leaf {
-        ::tt::Leaf::Ident(ident) => {
-            Some(Name::new_symbol_maybe_raw(ident.sym.clone(), ident.is_raw, ident.span.ctx))
-        }
+        ::tt::Leaf::Ident(ident) => Some(Name::new_symbol(ident.sym.clone(), ident.span.ctx)),
         _ => None,
     }));
     Some(ModPath { kind, segments })