Optimize in macro call directly

This excludes `panic_2015!` as calling it in the same manner results in
triggering the edition lint in a few places.

Author: jhpratt

Cargo.lock

@@ -3509,7 +3509,6 @@ dependencies = [
 name = "rustc_builtin_macros"
 version = "0.0.0"
 dependencies = [
- "rustc-literal-escaper",
  "rustc_ast",
  "rustc_ast_pretty",
  "rustc_attr_parsing",

compiler/rustc_builtin_macros/Cargo.toml

@@ -8,7 +8,6 @@ doctest = false
 
 [dependencies]
 # tidy-alphabetical-start
-rustc-literal-escaper = "0.0.5"
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }

compiler/rustc_builtin_macros/src/edition_panic.rs

@@ -1,9 +1,9 @@
-use rustc_ast::token::{Delimiter, Lit, LitKind, TokenKind};
-use rustc_ast::tokenstream::{TokenStream, TokenTree};
+use rustc_ast::token::Delimiter;
+use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::*;
 use rustc_expand::base::*;
 use rustc_span::edition::Edition;
-use rustc_span::{Ident, Span, Symbol, sym};
+use rustc_span::{Span, Symbol, sym};
 
 // Use an enum to ensure that no new macro calls are added without also updating the message in the
 // optimized path below.
@@ -67,55 +67,6 @@ fn expand<'cx>(
 ) -> MacroExpanderResult<'cx> {
     let sp = cx.with_call_site_ctxt(sp);
 
-    // If the call is of the form `panic!(<string literal>)` and there are no formatting arguments
-    // in the string literal, we can call `core::panicking::panic` to centralize the panic logic.
-    if tts.len() == 1
-        && let Some(TokenTree::Token(token, _)) = tts.get(0)
-        && let TokenKind::Literal(lit) = &token.kind
-        && let Lit { kind: LitKind::Str | LitKind::StrRaw(_), symbol, .. } = lit
-        && let msg = symbol.as_str()
-        && !msg.contains(|c| c == '{' || c == '}')
-    {
-        let msg = match mac {
-            InnerCall::Panic2015 | InnerCall::Panic2021 => cx.expr(sp, ExprKind::Lit(*lit)),
-            InnerCall::Unreachable2015 | InnerCall::Unreachable2021 => {
-                let msg = if msg.contains('\\') {
-                    let mut buf = String::with_capacity(msg.len());
-                    // Force-inlining here is aggressive but the closure is
-                    // called on every char in the string, so it can be hot in
-                    // programs with many long strings containing escapes.
-                    rustc_literal_escaper::unescape_str(
-                        msg,
-                        #[inline(always)]
-                        |_, res| match res {
-                            Ok(c) => buf.push(c),
-                            Err(err) => {
-                                assert!(!err.is_fatal(), "failed to unescape string literal")
-                            }
-                        },
-                    );
-                    buf
-                } else {
-                    msg.to_owned()
-                };
-
-                cx.expr_str(
-                    sp,
-                    Symbol::intern(&format!("internal error: entered unreachable code: {msg}")),
-                )
-            }
-        };
-
-        return ExpandResult::Ready(MacEager::expr(cx.expr_call(
-            sp,
-            cx.expr_path(cx.path_global(
-                sp,
-                [sym::core, sym::panicking, sym::panic].map(|sym| Ident::new(sym, sp)).to_vec(),
-            )),
-            [msg].into(),
-        )));
-    }
-
     ExpandResult::Ready(MacEager::expr(
         cx.expr_macro_call(
             sp,

library/core/src/lib.rs

@@ -184,6 +184,7 @@
 #![feature(staged_api)]
 #![feature(stmt_expr_attributes)]
 #![feature(strict_provenance_lints)]
+#![feature(super_let)]
 #![feature(trait_alias)]
 #![feature(transparent_unions)]
 #![feature(try_blocks)]

library/core/src/panic.rs

@@ -45,7 +45,7 @@ pub macro panic_2015 {
 
 #[doc(hidden)]
 #[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
-#[allow_internal_unstable(panic_internals, const_format_args)]
+#[allow_internal_unstable(panic_internals, const_format_args, super_let)]
 #[rustc_diagnostic_item = "core_panic_2021_macro"]
 #[rustc_macro_transparency = "semitransparent"]
 pub macro panic_2021 {
@@ -59,7 +59,11 @@ pub macro panic_2021 {
     ($($t:tt)+) => ({
         // Semicolon to prevent temporaries inside the formatting machinery from
         // being considered alive in the caller after the panic_fmt call.
-        $crate::panicking::panic_fmt($crate::const_format_args!($($t)+));
+        super let args = $crate::const_format_args!($($t)+);
+        if let $crate::option::Option::Some(s) = args.as_str() {
+            $crate::panicking::panic(s);
+        }
+        $crate::panicking::panic_fmt(args);
     }),
 }
 

tests/ui/consts/const-eval/const_panic-normalize-tabs-115498.rs

@@ -3,4 +3,3 @@
 struct Bug([u8; panic!{"\t"}]);
 //~^ ERROR evaluation panicked
 //~| NOTE: in this expansion of panic!
-//~| NOTE: failed here

tests/ui/panics/short-ice-remove-middle-frames-2.run.stderr

@@ -2,16 +2,14 @@
 thread 'main' ($TID) panicked at $DIR/short-ice-remove-middle-frames-2.rs:62:5:
 debug!!!
 stack backtrace:
-   0: __rustc::rust_begin_unwind
-   1: core::panicking::panic_fmt
-   2: core::panicking::panic
-   3: short_ice_remove_middle_frames_2::eight
-   4: short_ice_remove_middle_frames_2::seven::{{closure}}
+   0: std::panicking::begin_panic
+   1: short_ice_remove_middle_frames_2::eight
+   2: short_ice_remove_middle_frames_2::seven::{{closure}}
       [... omitted 3 frames ...]
-   5: short_ice_remove_middle_frames_2::fifth
-   6: short_ice_remove_middle_frames_2::fourth::{{closure}}
+   3: short_ice_remove_middle_frames_2::fifth
+   4: short_ice_remove_middle_frames_2::fourth::{{closure}}
       [... omitted 4 frames ...]
-   7: short_ice_remove_middle_frames_2::first
-   8: short_ice_remove_middle_frames_2::main
-   9: core::ops::function::FnOnce::call_once
+   5: short_ice_remove_middle_frames_2::first
+   6: short_ice_remove_middle_frames_2::main
+   7: core::ops::function::FnOnce::call_once
 note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

tests/ui/panics/short-ice-remove-middle-frames.run.stderr

@@ -2,16 +2,14 @@
 thread 'main' ($TID) panicked at $DIR/short-ice-remove-middle-frames.rs:58:5:
 debug!!!
 stack backtrace:
-   0: __rustc::rust_begin_unwind
-   1: core::panicking::panic_fmt
-   2: core::panicking::panic
-   3: short_ice_remove_middle_frames::seven
-   4: short_ice_remove_middle_frames::sixth
-   5: short_ice_remove_middle_frames::fifth::{{closure}}
+   0: std::panicking::begin_panic
+   1: short_ice_remove_middle_frames::seven
+   2: short_ice_remove_middle_frames::sixth
+   3: short_ice_remove_middle_frames::fifth::{{closure}}
       [... omitted 4 frames ...]
-   6: short_ice_remove_middle_frames::second
-   7: short_ice_remove_middle_frames::first::{{closure}}
-   8: short_ice_remove_middle_frames::first
-   9: short_ice_remove_middle_frames::main
-  10: core::ops::function::FnOnce::call_once
+   4: short_ice_remove_middle_frames::second
+   5: short_ice_remove_middle_frames::first::{{closure}}
+   6: short_ice_remove_middle_frames::first
+   7: short_ice_remove_middle_frames::main
+   8: core::ops::function::FnOnce::call_once
 note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.