Rollup merge of #64243 - petrochenkov:cmdattr, r=alexcrichton

Move injection of attributes from command line to `libsyntax_ext`

Just a tiny bit of code generation that wasn't moved into `libsyntax_ext` in https://github.com/rust-lang/rust/pull/62771.

src/libsyntax_ext/cmdline_attrs.rs

@@ -0,0 +1,30 @@
+//! Attributes injected into the crate root from command line using `-Z crate-attr`.
+
+use syntax::ast::{self, AttrStyle};
+use syntax::attr::mk_attr;
+use syntax::panictry;
+use syntax::parse::{self, token, ParseSess};
+use syntax_pos::FileName;
+
+pub fn inject(mut krate: ast::Crate, parse_sess: &ParseSess, attrs: &[String]) -> ast::Crate {
+    for raw_attr in attrs {
+        let mut parser = parse::new_parser_from_source_str(
+            parse_sess,
+            FileName::cli_crate_attr_source_code(&raw_attr),
+            raw_attr.clone(),
+        );
+
+        let start_span = parser.token.span;
+        let (path, tokens) = panictry!(parser.parse_meta_item_unrestricted());
+        let end_span = parser.token.span;
+        if parser.token != token::Eof {
+            parse_sess.span_diagnostic
+                .span_err(start_span.to(end_span), "invalid crate attribute");
+            continue;
+        }
+
+        krate.attrs.push(mk_attr(AttrStyle::Inner, path, tokens, start_span.to(end_span)));
+    }
+
+    krate
+}

src/libsyntax_ext/lib.rs

@@ -40,6 +40,7 @@ mod source_util;
 mod test;
 mod trace_macros;
 
+pub mod cmdline_attrs;
 pub mod plugin_macro_defs;
 pub mod proc_macro_harness;
 pub mod standard_library_imports;