test: add regression test for #6880

Covers all three parenthesized visibility qualifiers (pub(crate),
pub(super), pub(in path)) on tuple struct fields with long types,
plus pub with wrapping, named struct fields, and a short tuple field
as controls.

Author: jlizen

tests/source/issue-6880.rs

@@ -0,0 +1,21 @@
+struct PubCrate(
+    pub(crate) std::collections::HashMap<some::module::path::TypeNameA, some::module::path::TypeNameB>,
+);
+
+struct PubSuper(
+    pub(super) std::collections::HashMap<some::module::path::TypeNameA, some::module::path::TypeNameB>,
+);
+
+struct PubInPath(
+    pub(in some::module) std::collections::HashMap<some::module::path::TypeNameA, some::module::path::TypeNameB>,
+);
+
+struct PubPlain(
+    pub std::collections::HashMap<some::module::path::TypeNameAaaaaaaaaaa, some::module::path::TypeNameB>,
+);
+
+struct NamedPubCrate {
+    pub(crate) field: std::collections::HashMap<some::module::path::TypeNameA, some::module::path::TypeNameB>,
+}
+
+struct ShortPubCrate(pub(crate) u32);

tests/target/issue-6880.rs

@@ -0,0 +1,28 @@
+struct PubCrate(
+    pub(crate)
+        std::collections::HashMap<some::module::path::TypeNameA, some::module::path::TypeNameB>,
+);
+
+struct PubSuper(
+    pub(super)
+        std::collections::HashMap<some::module::path::TypeNameA, some::module::path::TypeNameB>,
+);
+
+struct PubInPath(
+    pub(in some::module)
+        std::collections::HashMap<some::module::path::TypeNameA, some::module::path::TypeNameB>,
+);
+
+struct PubPlain(
+    pub std::collections::HashMap<
+        some::module::path::TypeNameAaaaaaaaaaa,
+        some::module::path::TypeNameB,
+    >,
+);
+
+struct NamedPubCrate {
+    pub(crate) field:
+        std::collections::HashMap<some::module::path::TypeNameA, some::module::path::TypeNameB>,
+}
+
+struct ShortPubCrate(pub(crate) u32);