Forbid string literal suffix

askama_parser/src/lib.rs

@@ -687,7 +687,7 @@ fn str_lit<'a>(i: &mut &'a str) -> ParseResult<'a, StrLit<'a>> {
 }
 
 fn not_suffix_with_hash<'a>(i: &mut &'a str) -> ParseResult<'a, ()> {
-    if let Some(suffix) = opt((identifier, '#').take()).parse_next(i)? {
+    if let Some(suffix) = opt(identifier.take()).parse_next(i)? {
         return cut_error!(
             "you are missing a space to separate two string literals",
             suffix,

testing/tests/ui/macro-args.rs

@@ -0,0 +1,12 @@
+// This test ensures that the proc-macro fails if two arguments are not separated.
+
+use askama::Template;
+
+#[derive(Template)]
+#[template(
+    source = r###"{{e!{ r#""#r"  \ "}}}"###,
+    ext = "html"
+)]
+struct Example;
+
+fn main() {}

testing/tests/ui/macro-args.stderr

@@ -0,0 +1,7 @@
+error: you are missing a space to separate two string literals
+ --> <source attribute>:1:11
+       "r\"  \\ \"}}}"
+ --> tests/ui/macro-args.rs:7:14
+  |
+7 |     source = r###"{{e!{ r#""#r"  \ "}}}"###,
+  |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^