Add test coverage for proc-macro invalid tup index suffixes

Author: jieyouxu

tests/ui/parser/auxiliary/tuple-index-suffix-proc-macro-aux.rs

@@ -0,0 +1,33 @@
+#![feature(proc_macro_quote, proc_macro_span)]
+
+extern crate proc_macro;
+
+use proc_macro::{Ident, Literal, Span, TokenStream, TokenTree, quote};
+
+#[proc_macro]
+pub fn bad_tup_indexing(input: TokenStream) -> TokenStream {
+    let tt = input.into_iter().next().unwrap();
+    let TokenTree::Literal(indexing_expr) = tt else {
+        unreachable!();
+    };
+    quote! { (42,).$indexing_expr }
+}
+
+// Expects {IDENT, COMMA, LITERAL}
+#[proc_macro]
+pub fn bad_tup_struct_indexing(input: TokenStream) -> TokenStream {
+    let mut input = input.into_iter();
+
+    let id_tt = input.next().unwrap();
+    let _comma = input.next().unwrap();
+    let tt = input.next().unwrap();
+
+    let TokenTree::Ident(ident) = id_tt else {
+        unreachable!("id");
+    };
+    let TokenTree::Literal(indexing_expr) = tt else {
+        unreachable!("lit");
+    };
+
+    quote! { $ident.$indexing_expr }
+}

tests/ui/parser/tuple-index-suffix-proc-macro.rs

@@ -0,0 +1,31 @@
+//! See #59418.
+//!
+//! Like `tuple-index-suffix.rs`, but exercises the proc-macro interaction.
+
+//@ proc-macro: tuple-index-suffix-proc-macro-aux.rs
+
+extern crate tuple_index_suffix_proc_macro_aux;
+use tuple_index_suffix_proc_macro_aux as aux;
+
+fn main() {
+    struct TupStruct(i32);
+    let tup_struct = TupStruct(42);
+
+    // #60186 carve outs `{i,u}{32,usize}` as non-lint pseudo-FCW warnings.
+
+    aux::bad_tup_indexing!(0usize);
+    //~^ WARN suffixes on a tuple index are invalid
+    aux::bad_tup_struct_indexing!(tup_struct, 0isize);
+    //~^ WARN suffixes on a tuple index are invalid
+
+    // Not part of the #60186 carve outs.
+
+    aux::bad_tup_indexing!(0u8);
+    //~^ ERROR suffixes on a tuple index are invalid
+    aux::bad_tup_struct_indexing!(tup_struct, 0u64);
+    //~^ ERROR suffixes on a tuple index are invalid
+
+    // NOTE: didn't bother with trying to figure out how to generate `struct P { 0u32: u32 }` using
+    // *only* `proc_macro` without help with `syn`/`quote`, looks like you can't with just
+    // `proc_macro::quote`?
+}

tests/ui/parser/tuple-index-suffix-proc-macro.stderr

@@ -0,0 +1,34 @@
+warning: suffixes on a tuple index are invalid
+  --> $DIR/tuple-index-suffix-proc-macro.rs:16:28
+   |
+LL |     aux::bad_tup_indexing!(0usize);
+   |                            ^^^^^^ invalid suffix `usize`
+   |
+   = help: `usize` is *temporarily* accepted on tuple index fields as it was incorrectly accepted on stable for a few releases
+   = help: on proc macros, you'll want to use `syn::Index::from` or `proc_macro::Literal::*_unsuffixed` for code that will desugar to tuple field access
+   = help: see issue #60210 <https://github.com/rust-lang/rust/issues/60210> for more information
+
+warning: suffixes on a tuple index are invalid
+  --> $DIR/tuple-index-suffix-proc-macro.rs:18:47
+   |
+LL |     aux::bad_tup_struct_indexing!(tup_struct, 0isize);
+   |                                               ^^^^^^ invalid suffix `isize`
+   |
+   = help: `isize` is *temporarily* accepted on tuple index fields as it was incorrectly accepted on stable for a few releases
+   = help: on proc macros, you'll want to use `syn::Index::from` or `proc_macro::Literal::*_unsuffixed` for code that will desugar to tuple field access
+   = help: see issue #60210 <https://github.com/rust-lang/rust/issues/60210> for more information
+
+error: suffixes on a tuple index are invalid
+  --> $DIR/tuple-index-suffix-proc-macro.rs:23:28
+   |
+LL |     aux::bad_tup_indexing!(0u8);
+   |                            ^^^ invalid suffix `u8`
+
+error: suffixes on a tuple index are invalid
+  --> $DIR/tuple-index-suffix-proc-macro.rs:25:47
+   |
+LL |     aux::bad_tup_struct_indexing!(tup_struct, 0u64);
+   |                                               ^^^^ invalid suffix `u64`
+
+error: aborting due to 2 previous errors; 2 warnings emitted
+