Add regression test to cover additional cases

tests/ui/macros/meta-item-global-path-fail-issue-53048.rs

@@ -0,0 +1,18 @@
+// Regression test for https://github.com/rust-lang/rust/issues/53048/
+// This test ensures that invalid meta item or global path
+// is rejected by the compiler.
+
+macro_rules! m { ($m:meta) => { #[derive($m)] pub struct S; }; }
+
+m!(::);
+//~^ ERROR expected identifier, found `<eof>`
+
+// no segment after `::` to be a valid path
+#[derive(::)] pub struct D;
+//~^ ERROR expected unsuffixed literal, found `<eof>`
+
+// value must be a literal, not a path
+#[allow(a = ::b::c)]
+//~^ ERROR expected unsuffixed literal, found `::`
+
+fn main() {}

tests/ui/macros/meta-item-global-path-fail-issue-53048.stderr

@@ -0,0 +1,23 @@
+error: expected identifier, found `<eof>`
+  --> $DIR/meta-item-global-path-fail-issue-53048.rs:7:4
+   |
+LL | macro_rules! m { ($m:meta) => { #[derive($m)] pub struct S; }; }
+   |                   ------- while parsing argument for this `meta` macro fragment
+LL |
+LL | m!(::);
+   |    ^^ expected identifier
+
+error: expected unsuffixed literal, found `<eof>`
+  --> $DIR/meta-item-global-path-fail-issue-53048.rs:11:10
+   |
+LL | #[derive(::)] pub struct D;
+   |          ^^
+
+error: expected unsuffixed literal, found `::`
+  --> $DIR/meta-item-global-path-fail-issue-53048.rs:15:13
+   |
+LL | #[allow(a = ::b::c)]
+   |             ^^
+
+error: aborting due to 3 previous errors
+

tests/ui/macros/meta-item-global-path-issue-53048.rs

@@ -0,0 +1,15 @@
+// Regression test for https://github.com/rust-lang/rust/issues/53048/
+// This test ensures that a global path in a meta item is accepted by the compiler.
+// All examples are different ways of specifying the same path, and should all compile fine.
+//@ check-pass
+
+extern crate core;
+
+#[derive(::core::clone::Clone)] pub struct A;
+#[derive(Clone, ::core::marker::Copy)] pub struct C;
+#[cfg_attr(true, derive(::core::clone::Clone))] pub struct G;
+
+macro_rules! m { ($m:meta) => { #[derive($m)] pub struct S; }; }
+m!(::core::clone::Clone);
+
+fn main() {}