Rollup merge of #104199 - SarthakSingh31:issue-97417-1, r=cjgillot

Keep track of the start of the argument block of a closure

This removes a call to `tcx.sess.source_map()` from [compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs](https://github.com/rust-lang/rust/compare/master...SarthakSingh31:issue-97417-1?expand=1#diff-8406bbc0d0b43d84c91b1933305df896ecdba0d1f9269e6744f13d87a2ab268a) as required by #97417.

VsCode automatically applied `rustfmt` to the files I edited under `src/tools`. I can undo that if its a problem.

r? `@cjgillot`

Author: matthiaskrgr

src/closures.rs

@@ -335,6 +335,7 @@ pub(crate) fn rewrite_last_closure(
             ref fn_decl,
             ref body,
             fn_decl_span: _,
+            fn_arg_span: _,
         } = **closure;
         let body = match body.kind {
             ast::ExprKind::Block(ref block, _)