parser: r#self is not a valid raw identifier in macro calls

It's not a valid raw identifier anywhere, actually, but the other cases
(in a path, as a field name, as a macro name) were already handled.

Resolves <https://issues.oss-fuzz.com/issues/435218013>.

askama_parser/src/expr.rs

@@ -12,8 +12,8 @@ use winnow::token::{one_of, take_until};
 use crate::node::CondTest;
 use crate::{
     CharLit, ErrorContext, Level, Num, ParseResult, PathOrIdentifier, StrLit, StrPrefix, WithSpan,
-    char_lit, cut_error, filter, identifier, keyword, not_suffix_with_hash, num_lit,
-    path_or_identifier, skip_ws0, skip_ws1, str_lit, ws,
+    can_be_variable_name, char_lit, cut_error, filter, identifier, keyword, not_suffix_with_hash,
+    num_lit, path_or_identifier, skip_ws0, skip_ws1, str_lit, ws,
 };
 
 macro_rules! expr_prec_layer {
@@ -985,7 +985,7 @@ impl<'a> Suffix<'a> {
             } else if hashes == 0 {
                 // a simple identifier
                 Ok(())
-            } else if opt(identifier).parse_next(i)?.is_some() {
+            } else if let Some(id) = opt(identifier).parse_next(i)? {
                 // got a raw identifier
 
                 if str_kind.is_some() {
@@ -1005,7 +1005,11 @@ impl<'a> Suffix<'a> {
                     )
                 } else {
                     // a raw identifier like `r#async`
-                    Ok(())
+                    if !can_be_variable_name(id) {
+                        cut_error!(format!("`{id}` cannot be a raw identifier"), id)
+                    } else {
+                        Ok(())
+                    }
                 }
             } else {
                 cut_error!(

askama_parser/src/tests.rs

@@ -1632,3 +1632,18 @@ fn test_isolated_cr_in_raw_string() {
             .contains("a bare CR (Mac linebreak) is not allowed in string literals"),
     );
 }
+
+#[test]
+fn test_macro_call_illegal_raw_identifier() {
+    // Regression test for <https://issues.oss-fuzz.com/issues/435218013>.
+    let syntax = Syntax::default();
+
+    for id in ["crate", "self", "Self", "super"] {
+        assert!(
+            Ast::from_str(&format!("{{{{ z!(r#{id}) }}}}"), None, &syntax)
+                .unwrap_err()
+                .to_string()
+                .contains("cannot be a raw identifier"),
+        );
+    }
+}

fuzzing/fuzz/artifacts/derive/clusterfuzz-testcase-minimized-derive-6573215117017088

@@ -0,0 +1 @@
+ÿÿÿ{{z!{r#self}}}ÿ  ÿqÿø 

testing/tests/ui/raw-prefix.rs

@@ -120,4 +120,64 @@ struct UnseparatedPrefixedStrings2;
 #[template(source = r##"{{ z!(c""r#""#) }}"##, ext = "txt")]
 struct UnseparatedPrefixedStrings3;
 
+// `r#self`, `r#Self`, `r#crate` and `r#super` are not valid raw identifiers:
+// <https://doc.rust-lang.org/reference/identifiers.html>.
+// Regression test for <https://issues.oss-fuzz.com/issues/435218013>.
+
+#[derive(Template)]
+#[template(
+    source = "{{ z!(r#crate) }}",
+    ext = "txt"
+)]
+struct RawIdentifierCrate;
+
+#[derive(Template)]
+#[template(
+    source = "{{ z!(r#self) }}",
+    ext = "txt"
+)]
+struct RawIdentifierSelf;
+
+#[derive(Template)]
+#[template(
+    source = "{{ z!(r#Self) }}",
+    ext = "txt"
+)]
+struct RawIdentifierSelfTy;
+
+#[derive(Template)]
+#[template(
+    source = "{{ z!(r#super) }}",
+    ext = "txt"
+)]
+struct RawIdentifierSuper;
+
+#[derive(Template)]
+#[template(
+    source = "{{ z!(r##crate) }}",
+    ext = "txt"
+)]
+struct RawIdentifierCrateTooManyHashes;
+
+#[derive(Template)]
+#[template(
+    source = "{{ z!(r##self) }}",
+    ext = "txt"
+)]
+struct RawIdentifierSelfTooManyHashes;
+
+#[derive(Template)]
+#[template(
+    source = "{{ z!(r##Self) }}",
+    ext = "txt"
+)]
+struct RawIdentifierSelfTyTooManyHashes;
+
+#[derive(Template)]
+#[template(
+    source = "{{ z!(r##super) }}",
+    ext = "txt"
+)]
+struct RawIdentifierSuperTooManyHashes;
+
 fn main() {}

testing/tests/ui/raw-prefix.stderr

@@ -133,3 +133,67 @@ error: you are missing a space to separate two string literals
     |
 120 | #[template(source = r##"{{ z!(c""r#""#) }}"##, ext = "txt")]
     |                     ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: `crate` cannot be a raw identifier
+ --> <source attribute>:1:8
+       "crate) }}"
+   --> tests/ui/raw-prefix.rs:129:14
+    |
+129 |     source = "{{ z!(r#crate) }}",
+    |              ^^^^^^^^^^^^^^^^^^^
+
+error: `self` cannot be a raw identifier
+ --> <source attribute>:1:8
+       "self) }}"
+   --> tests/ui/raw-prefix.rs:136:14
+    |
+136 |     source = "{{ z!(r#self) }}",
+    |              ^^^^^^^^^^^^^^^^^^
+
+error: `Self` cannot be a raw identifier
+ --> <source attribute>:1:8
+       "Self) }}"
+   --> tests/ui/raw-prefix.rs:143:14
+    |
+143 |     source = "{{ z!(r#Self) }}",
+    |              ^^^^^^^^^^^^^^^^^^
+
+error: `super` cannot be a raw identifier
+ --> <source attribute>:1:8
+       "super) }}"
+   --> tests/ui/raw-prefix.rs:150:14
+    |
+150 |     source = "{{ z!(r#super) }}",
+    |              ^^^^^^^^^^^^^^^^^^^
+
+error: only one `#` is allowed in raw identifier delimitation
+ --> <source attribute>:1:6
+       "r##crate) }}"
+   --> tests/ui/raw-prefix.rs:157:14
+    |
+157 |     source = "{{ z!(r##crate) }}",
+    |              ^^^^^^^^^^^^^^^^^^^^
+
+error: only one `#` is allowed in raw identifier delimitation
+ --> <source attribute>:1:6
+       "r##self) }}"
+   --> tests/ui/raw-prefix.rs:164:14
+    |
+164 |     source = "{{ z!(r##self) }}",
+    |              ^^^^^^^^^^^^^^^^^^^
+
+error: only one `#` is allowed in raw identifier delimitation
+ --> <source attribute>:1:6
+       "r##Self) }}"
+   --> tests/ui/raw-prefix.rs:171:14
+    |
+171 |     source = "{{ z!(r##Self) }}",
+    |              ^^^^^^^^^^^^^^^^^^^
+
+error: only one `#` is allowed in raw identifier delimitation
+ --> <source attribute>:1:6
+       "r##super) }}"
+   --> tests/ui/raw-prefix.rs:178:14
+    |
+178 |     source = "{{ z!(r##super) }}",
+    |              ^^^^^^^^^^^^^^^^^^^^