Add regression test for impl blocks in const expr

tests/rustdoc/impl-in-const-block.rs

@@ -0,0 +1,43 @@
+// Regression test for #83026.
+// The goal of this test is to ensure that impl blocks inside
+// const expressions are documented as well.
+
+#![crate_name = "foo"]
+
+// @has 'foo/struct.A.html'
+// @has - '//*[@id="method.new"]/*[@class="code-header"]' 'pub fn new() -> A'
+// @has - '//*[@id="method.bar"]/*[@class="code-header"]' 'pub fn bar(&self)'
+// @has - '//*[@id="method.woo"]/*[@class="code-header"]' 'pub fn woo(&self)'
+// @has - '//*[@id="method.yoo"]/*[@class="code-header"]' 'pub fn yoo()'
+// @has - '//*[@id="method.yuu"]/*[@class="code-header"]' 'pub fn yuu()'
+pub struct A;
+
+const _: () = {
+    impl A {
+        const FOO: () = {
+            impl A {
+                pub fn woo(&self) {}
+            }
+        };
+
+        pub fn new() -> A {
+            A
+        }
+    }
+};
+pub const X: () = {
+    impl A {
+        pub fn bar(&self) {}
+    }
+};
+
+fn foo() {
+    impl A {
+        pub fn yoo() {}
+    }
+    const _: () = {
+        impl A {
+            pub fn yuu() {}
+        }
+    };
+}