Remove most version_check usage

Cargo.toml

@@ -30,13 +30,12 @@ optional = true
 default-features = false
 
 [dev-dependencies]
+version_check = "0.9"
 test-crate = { path = "./test-crate" }
 syn = { version = "2", features = ["full"] }
 trybuild = { version = "1.0.99", features = ["diff"] }
 
-[build-dependencies]
-version_check = "0.9"
-
 [features]
 default = ["syn-error"]
-syn-error = ["syn"]
+syn-error = ["dep:syn"]
+nightly = []

proc-macro-error-attr/Cargo.toml

@@ -20,6 +20,3 @@ targets = ["x86_64-unknown-linux-gnu"]
 [dependencies]
 quote = "1"
 proc-macro2 = "1"
-
-[build-dependencies]
-version_check = "0.9"

proc-macro-error-attr/src/lib.rs

@@ -81,7 +81,6 @@ fn impl_proc_macro_error(attr: TokenStream2, input: TokenStream2) -> Result<Toke
     Ok(res.into())
 }
 
-#[cfg(not(always_assert_unwind))]
 fn gen_body(block: TokenTree, settings: Settings) -> proc_macro2::TokenStream {
     let is_proc_macro_hack = settings.is_set(ProcMacroHack);
     let closure = if settings.is_set(AssertUnwindSafe) {
@@ -93,17 +92,6 @@ fn gen_body(block: TokenTree, settings: Settings) -> proc_macro2::TokenStream {
     quote!( ::proc_macro_error::entry_point(#closure, #is_proc_macro_hack) )
 }
 
-// FIXME:
-// proc_macro::TokenStream does not implement UnwindSafe until 1.37.0.
-// Considering this is the closure's return type the unwind safety check would fail
-// for virtually every closure possible, the check is meaningless.
-#[cfg(always_assert_unwind)]
-fn gen_body(block: TokenTree, settings: Settings) -> proc_macro2::TokenStream {
-    let is_proc_macro_hack = settings.is_set(ProcMacroHack);
-    let closure = quote!(::std::panic::AssertUnwindSafe(|| #block ));
-    quote!( ::proc_macro_error::entry_point(#closure, #is_proc_macro_hack) )
-}
-
 fn detect_proc_macro_hack(attrs: &[Attribute]) -> bool {
     attrs
         .iter()

src/imp/delegate.rs

@@ -38,7 +38,6 @@ pub(crate) fn emit_diagnostic(diag: Diagnostic) {
             IS_DIRTY.with(|c| c.set(true));
             PLevel::Error
         }
-        _ => unreachable!(),
     };
 
     let mut res = PDiag::spanned(span, level, msg);

src/lib.rs

@@ -271,7 +271,7 @@
 //! [`ToTokens`]: https://docs.rs/quote/1.0.3/quote/trait.ToTokens.html
 //!
 
-#![cfg_attr(not(use_fallback), feature(proc_macro_diagnostic))]
+#![cfg_attr(feature = "nightly", feature(proc_macro_diagnostic))]
 #![forbid(unsafe_code)]
 #![allow(clippy::needless_doctest_main)]
 
@@ -295,11 +295,11 @@ mod diagnostic;
 mod macros;
 mod sealed;
 
-#[cfg(use_fallback)]
+#[cfg(not(feature = "nightly"))]
 #[path = "imp/fallback.rs"]
 mod imp;
 
-#[cfg(not(use_fallback))]
+#[cfg(feature = "nightly")]
 #[path = "imp/delegate.rs"]
 mod imp;
 

tests/macro-errors.rs

@@ -1,6 +1,7 @@
-#[cfg_attr(skip_ui_tests, ignore)]
 #[test]
 fn ui() {
     let t = trybuild::TestCases::new();
-    t.compile_fail("tests/ui/*.rs");
+    if !version_check::Channel::read().is_some_and(|c| c.is_nightly()) {
+        t.compile_fail("tests/ui/*.rs");
+    }
 }