Auto merge of #65399 - Centril:rollup-6lzj0w5, r=Centril

Rollup of 7 pull requests

Successful merges:

 - #65215 (Add long error explanation for E0697)
 - #65292 (Print lifetimes with backticks)
 - #65362 (syntax: consolidate function parsing in item.rs)
 - #65363 (Remove implicit dependencies on syntax::pprust)
 - #65379 (refactor session::config::build_session_options_and_crate_config)
 - #65392 (Move `Nonterminal::to_tokenstream` to parser & don't rely directly on parser in lowering)
 - #65395 (Add some tests for fixed ICEs)

Failed merges:

r? @ghost

Author: bors

src/librustc/error_codes.rs

@@ -2005,6 +2005,24 @@ a (non-transparent) struct containing a single float, while `Grams` is a
 transparent wrapper around a float. This can make a difference for the ABI.
 "##,
 
+E0697: r##"
+A closure has been used as `static`.
+
+Erroneous code example:
+
+```compile_fail,E0697
+fn main() {
+    static || {}; // used as `static`
+}
+```
+
+Closures cannot be used as `static`. They "save" the environment,
+and as such a static closure would save only a static environment
+which would consist only of variables with a static lifetime. Given
+this it would be better to use a proper function. The easiest fix
+is to remove the `static` keyword.
+"##,
+
 E0698: r##"
 When using generators (or async) all type variables must be bound so a
 generator can be constructed.
@@ -2191,7 +2209,6 @@ See [RFC 2091] for details on this and other limitations.
     E0657, // `impl Trait` can only capture lifetimes bound at the fn level
     E0687, // in-band lifetimes cannot be used in `fn`/`Fn` syntax
     E0688, // in-band lifetimes cannot be mixed with explicit lifetime binders
-    E0697, // closures cannot be static
 //  E0707, // multiple elided lifetimes used in arguments of `async fn`
     E0708, // `async` non-`move` closures with parameters are not currently
            // supported

src/librustc/hir/lowering.rs

@@ -70,7 +70,8 @@ use syntax::print::pprust;
 use syntax::source_map::{respan, ExpnData, ExpnKind, DesugaringKind, Spanned};
 use syntax::symbol::{kw, sym, Symbol};
 use syntax::tokenstream::{TokenStream, TokenTree};
-use syntax::parse::token::{self, Token};
+use syntax::parse::token::{self, Nonterminal, Token};
+use syntax::parse::ParseSess;
 use syntax::visit::{self, Visitor};
 use syntax_pos::Span;
 
@@ -86,6 +87,11 @@ pub struct LoweringContext<'a> {
 
     resolver: &'a mut dyn Resolver,
 
+    /// HACK(Centril): there is a cyclic dependency between the parser and lowering
+    /// if we don't have this function pointer. To avoid that dependency so that
+    /// librustc is independent of the parser, we use dynamic dispatch here.
+    nt_to_tokenstream: NtToTokenstream,
+
     /// The items being lowered are collected here.
     items: BTreeMap<hir::HirId, hir::Item>,
 
@@ -180,6 +186,8 @@ pub trait Resolver {
     fn has_derives(&self, node_id: NodeId, derives: SpecialDerives) -> bool;
 }
 
+type NtToTokenstream = fn(&Nonterminal, &ParseSess, Span) -> TokenStream;
+
 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
 /// and if so, what meaning it has.
 #[derive(Debug)]
@@ -236,6 +244,7 @@ pub fn lower_crate(
     dep_graph: &DepGraph,
     krate: &Crate,
     resolver: &mut dyn Resolver,
+    nt_to_tokenstream: NtToTokenstream,
 ) -> hir::Crate {
     // We're constructing the HIR here; we don't care what we will
     // read, since we haven't even constructed the *input* to
@@ -249,6 +258,7 @@ pub fn lower_crate(
         sess,
         cstore,
         resolver,
+        nt_to_tokenstream,
         items: BTreeMap::new(),
         trait_items: BTreeMap::new(),
         impl_items: BTreeMap::new(),
@@ -1022,7 +1032,7 @@ impl<'a> LoweringContext<'a> {
     fn lower_token(&mut self, token: Token) -> TokenStream {
         match token.kind {
             token::Interpolated(nt) => {
-                let tts = nt.to_tokenstream(&self.sess.parse_sess, token.span);
+                let tts = (self.nt_to_tokenstream)(&nt, &self.sess.parse_sess, token.span);
                 self.lower_token_stream(tts)
             }
             _ => TokenTree::Token(token).into(),