Test basic hygiene for macro_rules produced by transparent macros

src/test/ui/proc-macro/auxiliary/gen-macro-rules-hygiene.rs

@@ -0,0 +1,23 @@
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::*;
+
+#[proc_macro]
+pub fn gen_macro_rules(_: TokenStream) -> TokenStream {
+    "
+    macro_rules! generated {() => {
+        struct ItemDef;
+        let local_def = 0;
+
+        ItemUse; // OK
+        local_use; // ERROR
+        break 'label_use; // ERROR
+
+        type DollarCrate = $crate::ItemUse; // OK
+    }}
+    ".parse().unwrap()
+}

src/test/ui/proc-macro/gen-macro-rules-hygiene.rs

@@ -0,0 +1,23 @@
+// `macro_rules` items produced by transparent macros have correct hygiene in basic cases.
+// Local variables and labels are hygienic, items are not hygienic.
+// `$crate` refers to the crate that defines `macro_rules` and not the outer transparent macro.
+
+// aux-build:gen-macro-rules-hygiene.rs
+
+#[macro_use]
+extern crate gen_macro_rules_hygiene;
+
+struct ItemUse;
+
+gen_macro_rules!();
+//~^ ERROR use of undeclared label `'label_use`
+//~| ERROR cannot find value `local_use` in this scope
+
+fn main() {
+    'label_use: loop {
+        let local_use = 1;
+        generated!();
+        ItemDef; // OK
+        local_def; //~ ERROR cannot find value `local_def` in this scope
+    }
+}

src/test/ui/proc-macro/gen-macro-rules-hygiene.stderr

@@ -0,0 +1,28 @@
+error[E0426]: use of undeclared label `'label_use`
+  --> $DIR/gen-macro-rules-hygiene.rs:12:1
+   |
+LL | gen_macro_rules!();
+   | ^^^^^^^^^^^^^^^^^^^ undeclared label `'label_use`
+...
+LL |         generated!();
+   |         ------------- in this macro invocation
+
+error[E0425]: cannot find value `local_use` in this scope
+  --> $DIR/gen-macro-rules-hygiene.rs:12:1
+   |
+LL | gen_macro_rules!();
+   | ^^^^^^^^^^^^^^^^^^^ not found in this scope
+...
+LL |         generated!();
+   |         ------------- in this macro invocation
+
+error[E0425]: cannot find value `local_def` in this scope
+  --> $DIR/gen-macro-rules-hygiene.rs:21:9
+   |
+LL |         local_def;
+   |         ^^^^^^^^^ not found in this scope
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0425, E0426.
+For more information about an error, try `rustc --explain E0425`.