Auto merge of rust-lang#127524 - oli-obk:feed_item_attrs2, r=<try>

Make ast `MutVisitor` have the same method name and style as `Visitor`

It doesn't map 100% because some `MutVisitor` methods can filter or even expand to multiple items, but consistency seems nicer.

The last commit showcases how similar they are by changing ast validation to a `MutVisitor` (without actually doing any mutation yet). My plan is to replace all nodes that support it with error nodes if validation failed on them. This allows ast lowering to just assume things are error or valid, and avoids having to redo some checks, delaying bugs or checking the global error counter.

tracking issue: rust-lang#127615

Cargo.lock

@@ -3638,6 +3638,7 @@ dependencies = [
  "rustc_session",
  "rustc_span",
  "rustc_target",
+ "smallvec",
  "thin-vec",
 ]
 

compiler/rustc_ast/src/ast.rs

@@ -1883,9 +1883,14 @@ pub enum LitKind {
 
 impl LitKind {
     pub fn str(&self) -> Option<Symbol> {
+        self.try_str().ok()?
+    }
+
+    pub fn try_str(&self) -> Result<Option<Symbol>, ErrorGuaranteed> {
         match *self {
-            LitKind::Str(s, _) => Some(s),
-            _ => None,
+            LitKind::Str(s, _) => Ok(Some(s)),
+            LitKind::Err(guar) => Err(guar),
+            _ => Ok(None),
         }
     }
 
@@ -2827,6 +2832,15 @@ pub enum AttrKind {
     DocComment(CommentKind, Symbol),
 }
 
+impl AttrKind {
+    pub fn normal_mut(&mut self) -> &mut AttrItem {
+        match self {
+            AttrKind::Normal(normal) => &mut normal.item,
+            AttrKind::DocComment(..) => panic!("unexpected doc comment"),
+        }
+    }
+}
+
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct NormalAttr {
     pub item: AttrItem,

compiler/rustc_ast/src/attr/mod.rs

@@ -14,7 +14,7 @@ use crate::util::comments;
 use crate::util::literal::escape_string_symbol;
 use rustc_index::bit_set::GrowableBitSet;
 use rustc_span::symbol::{sym, Ident, Symbol};
-use rustc_span::Span;
+use rustc_span::{ErrorGuaranteed, Span};
 use smallvec::{smallvec, SmallVec};
 use std::iter;
 use std::sync::atomic::{AtomicU32, Ordering};
@@ -144,9 +144,13 @@ impl Attribute {
     }
 
     pub fn value_str(&self) -> Option<Symbol> {
+        self.try_value_str().ok()?
+    }
+
+    pub fn try_value_str(&self) -> Result<Option<Symbol>, ErrorGuaranteed> {
         match &self.kind {
-            AttrKind::Normal(normal) => normal.item.value_str(),
-            AttrKind::DocComment(..) => None,
+            AttrKind::Normal(normal) => normal.item.try_value_str(),
+            AttrKind::DocComment(..) => Ok(None),
         }
     }
 
@@ -236,9 +240,13 @@ impl AttrItem {
     }
 
     fn value_str(&self) -> Option<Symbol> {
+        self.try_value_str().ok()?
+    }
+
+    fn try_value_str(&self) -> Result<Option<Symbol>, ErrorGuaranteed> {
         match &self.args {
             AttrArgs::Eq(_, args) => args.value_str(),
-            AttrArgs::Delimited(_) | AttrArgs::Empty => None,
+            AttrArgs::Delimited(_) | AttrArgs::Empty => Ok(None),
         }
     }
 
@@ -257,15 +265,17 @@ impl AttrItem {
 }
 
 impl AttrArgsEq {
-    fn value_str(&self) -> Option<Symbol> {
+    fn value_str(&self) -> Result<Option<Symbol>, ErrorGuaranteed> {
         match self {
             AttrArgsEq::Ast(expr) => match expr.kind {
-                ExprKind::Lit(token_lit) => {
-                    LitKind::from_token_lit(token_lit).ok().and_then(|lit| lit.str())
-                }
-                _ => None,
+                ExprKind::Lit(token_lit) => LitKind::from_token_lit(token_lit)
+                    .ok()
+                    .and_then(|lit| lit.try_str().transpose())
+                    .transpose(),
+                ExprKind::Err(guar) => Err(guar),
+                _ => Ok(None),
             },
-            AttrArgsEq::Hir(lit) => lit.kind.str(),
+            AttrArgsEq::Hir(lit) => lit.kind.try_str(),
         }
     }
 }