1 files changed, 82 insertions, 0 deletions
diff --git a/src/test/rustdoc/hide-complex-unevaluated-const-arguments.rs b/src/test/rustdoc/hide-complex-unevaluated-const-arguments.rs
new file mode 100644
index 000000000..644a6e1cf
--- /dev/null
+++ b/src/test/rustdoc/hide-complex-unevaluated-const-arguments.rs
@@ -0,0 +1,82 @@
+// Test that certain unevaluated constant expression arguments that are
+// deemed too verbose or complex and that may leak private or
+// `doc(hidden)` struct fields are not displayed in the documentation.
+//
+// Read the documentation of `rustdoc::clean::utils::print_const_expr`
+// for further details.
+#![feature(const_trait_impl, generic_const_exprs)]
+#![allow(incomplete_features)]
+
+// @has hide_complex_unevaluated_const_arguments/trait.Stage.html
+pub trait Stage {
+    // A helper constant that prevents const expressions containing it
+    // from getting fully evaluated since it doesn't have a body and
+    // thus is non-reducible. This allows us to specifically test the
+    // pretty-printing of *unevaluated* consts.
+    const ABSTRACT: usize;
+
+    // Currently considered "overly complex" by the `generic_const_exprs`
+    // feature. If / once this expression kind gets supported, this
+    // unevaluated const expression could leak the private struct field.
+    //
+    // FIXME: Once the line below compiles, make this a test that
+    //        ensures that the private field is not printed.
+    //
+    //const ARRAY0: [u8; Struct { private: () } + Self::ABSTRACT];
+
+    // This assoc. const could leak the private assoc. function `Struct::new`.
+    // Ensure that this does not happen.
+    //
+    // @has - '//*[@id="associatedconstant.ARRAY1"]' \
+    //        'const ARRAY1: [u8; { _ }]'
+    const ARRAY1: [u8; Struct::new(/* ... */) + Self::ABSTRACT * 1_000];
+
+    // @has - '//*[@id="associatedconstant.VERBOSE"]' \
+    //        'const VERBOSE: [u16; { _ }]'
+    const VERBOSE: [u16; compute("thing", 9 + 9) * Self::ABSTRACT];
+
+    // Check that we do not leak the private struct field contained within
+    // the path. The output could definitely be improved upon
+    // (e.g. printing sth. akin to `<Self as Helper<{ _ }>>::OUT`) but
+    // right now “safe is safe”.
+    //
+    // @has - '//*[@id="associatedconstant.PATH"]' \
+    //        'const PATH: usize = _'
+    const PATH: usize = <Self as Helper<{ Struct { private: () } }>>::OUT;
+}
+
+const fn compute(input: &str, extra: usize) -> usize {
+    input.len() + extra
+}
+
+pub trait Helper<const S: Struct> {
+    const OUT: usize;
+}
+
+impl<const S: Struct, St: Stage + ?Sized> Helper<S> for St {
+    const OUT: usize = St::ABSTRACT;
+}
+
+// Currently in rustdoc, const arguments are not evaluated in this position
+// and therefore they fall under the realm of `print_const_expr`.
+// If rustdoc gets patched to evaluate const arguments, it is fine to replace
+// this test as long as one can ensure that private fields are not leaked!
+//
+// @has hide_complex_unevaluated_const_arguments/trait.Sub.html \
+//      '//*[@class="rust trait"]' \
+//      'pub trait Sub: Sup<{ _ }, { _ }> { }'
+pub trait Sub: Sup<{ 90 * 20 * 4 }, { Struct { private: () } }> {}
+
+pub trait Sup<const N: usize, const S: Struct> {}
+
+pub struct Struct { private: () }
+
+impl Struct {
+    const fn new() -> Self { Self { private: () } }
+}
+
+impl const std::ops::Add<usize> for Struct {
+    type Output = usize;
+
+    fn add(self, _: usize) -> usize { 0 }
+}