fix: Overlapping spans in delimited meta-vars

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -236,6 +236,13 @@ fn expand_macro<'cx>(
                             target_sp.open = source_sp.open.with_ctxt(ctxt);
                             target_sp.close = source_sp.close.with_ctxt(ctxt);
                         }
+                        (
+                            TokenTree::Delimited(target_sp, ..),
+                            mbe::TokenTree::MetaVar(source_sp, ..),
+                        ) => {
+                            target_sp.open = source_sp.with_ctxt(ctxt);
+                            target_sp.close = source_sp.with_ctxt(ctxt).shrink_to_hi();
+                        }
                         _ => {
                             let sp = rhs_tt.span().with_ctxt(ctxt);
                             tt.set_span(sp);

tests/ui/macros/issue-118786.rs

@@ -0,0 +1,16 @@
+// compile-flags: --crate-type lib -O -C debug-assertions=yes
+
+// Regression test for issue 118786
+
+macro_rules! make_macro {
+    ($macro_name:tt) => {
+        macro_rules! $macro_name {
+        //~^ ERROR macros that expand to items must be delimited with braces or followed by a semicolon
+        //~| ERROR macro expansion ignores token `{` and any following
+        //~| ERROR cannot find macro `macro_rules` in this scope
+            () => {}
+        }
+    }
+}
+
+make_macro!((meow));

tests/ui/macros/issue-118786.stderr

@@ -0,0 +1,47 @@
+error: macros that expand to items must be delimited with braces or followed by a semicolon
+  --> $DIR/issue-118786.rs:7:22
+   |
+LL |         macro_rules! $macro_name {
+   |                      ^^^^^^^^^^^
+   |
+help: change the delimiters to curly braces
+   |
+LL |         macro_rules! {} {
+   |                      ~          +
+help: add a semicolon
+   |
+LL |         macro_rules! $macro_name; {
+   |                                 +
+
+error: macro expansion ignores token `{` and any following
+  --> $DIR/issue-118786.rs:7:34
+   |
+LL |         macro_rules! $macro_name {
+   |                                  ^
+...
+LL | make_macro!((meow));
+   | ------------------- caused by the macro expansion here
+   |
+   = note: the usage of `make_macro!` is likely invalid in item context
+
+error: cannot find macro `macro_rules` in this scope
+  --> $DIR/issue-118786.rs:7:9
+   |
+LL |         macro_rules! $macro_name {
+   |         ^^^^^^^^^^^
+...
+LL | make_macro!((meow));
+   | ------------------- in this macro invocation
+   |
+note: maybe you have forgotten to define a name for this `macro_rules!`
+  --> $DIR/issue-118786.rs:7:9
+   |
+LL |         macro_rules! $macro_name {
+   |         ^^^^^^^^^^^
+...
+LL | make_macro!((meow));
+   | ------------------- in this macro invocation
+   = note: this error originates in the macro `make_macro` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 3 previous errors
+