Add regression tests for token hygiene annotations in macro bodies

Add `unpretty-debug-shadow` test covering macro body tokens that
reference a shadowed variable, and simplify the `unpretty-debug-metavars`
test macro.

Signed-off-by: Andrew V. Teylu <andrew.teylu@vector.com>

tests/ui/hygiene/unpretty-debug-metavars.rs

@@ -1,9 +1,10 @@
 //@ check-pass
 //@ compile-flags: -Zunpretty=expanded,hygiene
 
-// Regression test: metavar parameters in macro-generated macro_rules!
-// definitions should have hygiene annotations so that textually identical
-// `$marg` bindings are distinguishable by their syntax contexts.
+// Regression test for token hygiene annotations in -Zunpretty=expanded,hygiene
+// Previously, metavar parameters in macro-generated macro_rules! definitions
+// were missing hygiene annotations, making identical `$marg` bindings
+// indistinguishable.
 
 // Don't break whenever Symbol numbering changes
 //@ normalize-stdout: "\d+#" -> "0#"

tests/ui/hygiene/unpretty-debug-metavars.stdout

@@ -1,9 +1,10 @@
 //@ check-pass
 //@ compile-flags: -Zunpretty=expanded,hygiene
 
-// Regression test: metavar parameters in macro-generated macro_rules!
-// definitions should have hygiene annotations so that textually identical
-// `$marg` bindings are distinguishable by their syntax contexts.
+// Regression test for token hygiene annotations in -Zunpretty=expanded,hygiene
+// Previously, metavar parameters in macro-generated macro_rules! definitions
+// were missing hygiene annotations, making identical `$marg` bindings
+// indistinguishable.
 
 // Don't break whenever Symbol numbering changes
 //@ normalize-stdout: "\d+#" -> "0#"

tests/ui/hygiene/unpretty-debug-shadow.rs

@@ -0,0 +1,20 @@
+//@ check-pass
+//@ compile-flags: -Zunpretty=expanded,hygiene
+
+// Regression test for token hygiene annotations in -Zunpretty=expanded,hygiene
+// Previously, tokens in macro_rules! bodies were missing hygiene annotations,
+// making it impossible to see how a macro's reference to a shadowed variable
+// is distinguished from the shadowing binding.
+
+// Don't break whenever Symbol numbering changes
+//@ normalize-stdout: "\d+#" -> "0#"
+
+#![feature(no_core)]
+#![no_core]
+
+fn f() {
+    let x = 0;
+    macro_rules! use_x { () => { x }; }
+    let x = 1;
+    use_x!();
+}

tests/ui/hygiene/unpretty-debug-shadow.stdout

@@ -0,0 +1,30 @@
+//@ check-pass
+//@ compile-flags: -Zunpretty=expanded,hygiene
+
+// Regression test for token hygiene annotations in -Zunpretty=expanded,hygiene
+// Previously, tokens in macro_rules! bodies were missing hygiene annotations,
+// making it impossible to see how a macro's reference to a shadowed variable
+// is distinguished from the shadowing binding.
+
+// Don't break whenever Symbol numbering changes
+//@ normalize-stdout: "\d+#" -> "0#"
+
+#![feature /* 0#0 */(no_core /* 0#0 */)]
+#![no_core /* 0#0 */]
+
+fn f /* 0#0 */() {
+    let x /* 0#0 */ = 0;
+    macro_rules! use_x /* 0#0 */ { () => { x /* 0#0 */ }; }
+    let x /* 0#0 */ = 1;
+    x /* 0#1 */;
+}
+
+/*
+Expansions:
+crate0::{{expn0}}: parent: crate0::{{expn0}}, call_site_ctxt: #0, def_site_ctxt: #0, kind: Root
+crate0::{{expn1}}: parent: crate0::{{expn0}}, call_site_ctxt: #0, def_site_ctxt: #0, kind: Macro(Bang, "use_x")
+
+SyntaxContexts:
+#0: parent: #0, outer_mark: (crate0::{{expn0}}, Opaque)
+#1: parent: #0, outer_mark: (crate0::{{expn1}}, SemiOpaque)
+*/