Rollup merge of rust-lang#146340 - fmease:frontmatter-containment, r=fee1-dead,Urgau

Strip frontmatter in fewer places

* Stop stripping frontmatter in `proc_macro::Literal::from_str` (RUST-146132)
* Stop stripping frontmatter in expr-ctxt (but not item-ctxt!) `include`s (RUST-145945)
* Stop stripping shebang (!) in `proc_macro::Literal::from_str`
  * Not a breaking change because it did compare spans already to ensure there wasn't extra whitespace or comments (`Literal::from_str("#!\n0")` already yields `Err(_)` thankfully!)
* Stop stripping frontmatter+shebang inside some rustdoc code where it doesn't make any observable difference (see self review comments)
* (Stop stripping frontmatter+shebang inside internal test code)

Fixes rust-lang#145945.
Fixes rust-lang#146132.

r? fee1-dead

Author: matthiaskrgr

clippy_lints/src/doc/needless_doctest_main.rs

@@ -8,6 +8,7 @@ use rustc_ast::{CoroutineKind, Fn, FnRetTy, Item, ItemKind};
 use rustc_errors::emitter::HumanEmitter;
 use rustc_errors::{Diag, DiagCtxt};
 use rustc_lint::LateContext;
+use rustc_parse::lexer::StripTokens;
 use rustc_parse::new_parser_from_source_str;
 use rustc_parse::parser::ForceCollect;
 use rustc_session::parse::ParseSess;
@@ -49,13 +50,14 @@ pub fn check(
                 let sm = Arc::new(SourceMap::new(FilePathMapping::empty()));
                 let psess = ParseSess::with_dcx(dcx, sm);
 
-                let mut parser = match new_parser_from_source_str(&psess, filename, code) {
-                    Ok(p) => p,
-                    Err(errs) => {
-                        errs.into_iter().for_each(Diag::cancel);
-                        return (false, test_attr_spans);
-                    },
-                };
+                let mut parser =
+                    match new_parser_from_source_str(&psess, filename, code, StripTokens::ShebangAndFrontmatter) {
+                        Ok(p) => p,
+                        Err(errs) => {
+                            errs.into_iter().for_each(Diag::cancel);
+                            return (false, test_attr_spans);
+                        },
+                    };
 
                 let mut relevant_main_found = false;
                 let mut eligible = true;