Rollup merge of #138682 - Alexendoo:extra-symbols, r=fee1-dead

Allow drivers to supply a list of extra symbols to intern

Allows adding new symbols as `const`s in external drivers, desirable in Clippy so we can use them in patterns to replace code like https://github.com/rust-lang/rust/blob/75530e9f72a1990ed2305e16fd51d02f47048f12/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs#L66

The Clippy change adds a couple symbols as a demo, the exact `clippy_utils` API and replacing other usages can be done on the Clippy side to minimise sync conflicts

---

try-job: aarch64-gnu

7 files changed, 33 insertions, 6 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 94c170d73af..f5a8e3dc387 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,6 +25,7 @@ path = "src/driver.rs"
 [dependencies]
 clippy_config = { path = "clippy_config" }
 clippy_lints = { path = "clippy_lints" }
+clippy_utils = { path = "clippy_utils" }
 rustc_tools_util = { path = "rustc_tools_util", version = "0.4.2" }
 tempfile = { version = "3.3", optional = true }
 termize = "0.1"
diff --git a/clippy_lints/src/attrs/deprecated_cfg_attr.rs b/clippy_lints/src/attrs/deprecated_cfg_attr.rs
index cd38aed26a3..7fab97d3ea1 100644
--- a/clippy_lints/src/attrs/deprecated_cfg_attr.rs
+++ b/clippy_lints/src/attrs/deprecated_cfg_attr.rs
@@ -1,10 +1,10 @@
 use super::{Attribute, DEPRECATED_CFG_ATTR, DEPRECATED_CLIPPY_CFG_ATTR, unnecessary_clippy_cfg};
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::msrvs::{self, MsrvStack};
+use clippy_utils::sym;
 use rustc_ast::AttrStyle;
 use rustc_errors::Applicability;
 use rustc_lint::EarlyContext;
-use rustc_span::sym;
 
 pub(super) fn check(cx: &EarlyContext<'_>, attr: &Attribute, msrv: &MsrvStack) {
     // check cfg_attr
@@ -18,7 +18,7 @@ pub(super) fn check(cx: &EarlyContext<'_>, attr: &Attribute, msrv: &MsrvStack) {
             && msrv.meets(msrvs::TOOL_ATTRIBUTES)
             // check for `rustfmt_skip` and `rustfmt::skip`
             && let Some(skip_item) = &items[1].meta_item()
-            && (skip_item.has_name(sym!(rustfmt_skip))
+            && (skip_item.has_name(sym::rustfmt_skip)
                 || skip_item
                     .path
                     .segments
diff --git a/clippy_lints/src/attrs/useless_attribute.rs b/clippy_lints/src/attrs/useless_attribute.rs
index e3e081ce08e..1cb43ab02a3 100644
--- a/clippy_lints/src/attrs/useless_attribute.rs
+++ b/clippy_lints/src/attrs/useless_attribute.rs
@@ -2,10 +2,10 @@ use super::USELESS_ATTRIBUTE;
 use super::utils::{is_lint_level, is_word, namespace_and_lint};
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::source::{SpanRangeExt, first_line_of_span};
+use clippy_utils::sym;
 use rustc_ast::{Attribute, Item, ItemKind};
 use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, LintContext};
-use rustc_span::sym;
 
 pub(super) fn check(cx: &EarlyContext<'_>, item: &Item, attrs: &[Attribute]) {
     let skip_unused_imports = attrs.iter().any(|attr| attr.has_name(sym::macro_use));
@@ -61,7 +61,7 @@ pub(super) fn check(cx: &EarlyContext<'_>, item: &Item, attrs: &[Attribute]) {
                             if is_word(lint, sym::unused_imports) && skip_unused_imports {
                                 return;
                             }
-                            if is_word(lint, sym!(unused_extern_crates)) {
+                            if is_word(lint, sym::unused_extern_crates) {
                                 return;
                             }
                         },
diff --git a/clippy_lints/src/doc/needless_doctest_main.rs b/clippy_lints/src/doc/needless_doctest_main.rs
index f6c10da1596..bf549dcdb50 100644
--- a/clippy_lints/src/doc/needless_doctest_main.rs
+++ b/clippy_lints/src/doc/needless_doctest_main.rs
@@ -38,7 +38,7 @@ pub fn check(
     // of all `#[test]` attributes in not ignored code examples
     fn check_code_sample(code: String, edition: Edition, ignore: bool) -> (bool, Vec<Range<usize>>) {
         rustc_driver::catch_fatal_errors(|| {
-            rustc_span::create_session_globals_then(edition, None, || {
+            rustc_span::create_session_globals_then(edition, &[], None, || {
                 let mut test_attr_spans = vec![];
                 let filename = FileName::anon_source_code(&code);
 
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index bcb0f8349e2..2ba70c44151 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -3,6 +3,7 @@
 #![feature(f128)]
 #![feature(f16)]
 #![feature(if_let_guard)]
+#![feature(macro_metavar_expr)]
 #![feature(macro_metavar_expr_concat)]
 #![feature(let_chains)]
 #![feature(never_type)]
@@ -74,6 +75,7 @@ pub mod qualify_min_const_fn;
 pub mod source;
 pub mod str_utils;
 pub mod sugg;
+pub mod sym;
 pub mod ty;
 pub mod usage;
 pub mod visitors;
@@ -126,7 +128,7 @@ use rustc_middle::ty::{
 use rustc_span::hygiene::{ExpnKind, MacroKind};
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{Ident, Symbol, kw};
-use rustc_span::{InnerSpan, Span, sym};
+use rustc_span::{InnerSpan, Span};
 use visitors::{Visitable, for_each_unconsumed_temporary};
 
 use crate::consts::{ConstEvalCtxt, Constant, mir_to_const};
diff --git a/clippy_utils/src/sym.rs b/clippy_utils/src/sym.rs
new file mode 100644
index 00000000000..9cc72a5b3aa
--- /dev/null
+++ b/clippy_utils/src/sym.rs
@@ -0,0 +1,23 @@
+#![allow(non_upper_case_globals)]
+
+use rustc_span::symbol::{Symbol, PREDEFINED_SYMBOLS_COUNT};
+
+pub use rustc_span::sym::*;
+
+macro_rules! generate {
+    ($($sym:ident,)*) => {
+        /// To be supplied to `rustc_interface::Config`
+        pub const EXTRA_SYMBOLS: &[&str] = &[
+            $(stringify!($sym),)*
+        ];
+
+        $(
+            pub const $sym: Symbol = Symbol::new(PREDEFINED_SYMBOLS_COUNT + ${index()});
+        )*
+    };
+}
+
+generate! {
+    rustfmt_skip,
+    unused_extern_crates,
+}
diff --git a/src/driver.rs b/src/driver.rs
index e4092bcd105..df9c4e8e6ae 100644
--- a/src/driver.rs
+++ b/src/driver.rs
@@ -160,6 +160,7 @@ impl rustc_driver::Callbacks for ClippyCallbacks {
             clippy_lints::register_lints(lint_store, conf);
             clippy_lints::register_pre_expansion_lints(lint_store, conf);
         }));
+        config.extra_symbols = clippy_utils::sym::EXTRA_SYMBOLS.into();
 
         // FIXME: #4825; This is required, because Clippy lints that are based on MIR have to be
         // run on the unoptimized MIR. On the other hand this results in some false negatives. If