implement struct_now_doc_hidden lint

src/lints/struct_now_doc_hidden.ron

@@ -0,0 +1,50 @@
+SemverQuery(
+    id: "struct_now_doc_hidden",
+    human_readable_name: "pub struct is now #[doc(hidden)]",
+    description: "A pub struct is now hidden from documentation effectively removing it from the crate's public api.",
+    required_update: Major,
+    reference_link: Some("https://doc.rust-lang.org/rustdoc/write-documentation/the-doc-attribute.html#hidden"),
+    query: r#"
+    {
+        CrateDiff {
+            baseline {
+                item {
+                    ... on Struct {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+                        struct_type @output @tag
+
+                        importable_path {
+                            path @output @tag
+                            public_api @filter(op: "=", value: ["$true"])
+                        }
+                    }
+                }
+            }
+            current {
+                item {
+                    ... on Struct {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+                        struct_name: name @output
+                        struct_type @filter(op: "=", value: ["%struct_type"])
+
+                        importable_path {
+                            path @filter(op: "=", value: ["%path"])
+                            public_api @filter(op: "!=", value: ["$true"])
+                        }
+
+                        span_: span @optional {
+                            filename @output
+                            begin_line @output
+                        }
+                    }
+                }
+            }
+        }
+    }"#,
+    arguments: {
+        "public": "public",
+        "true": true,
+    },
+    error_message: "A publicly visible struct is now hidden via #[doc(hidden)].",
+    per_result_error_template: Some("Struct {{struct_name}} in file {{span_filename}}:{{span_begin_line}}"),
+)

src/query.rs

@@ -495,6 +495,7 @@ add_lints!(
     struct_marked_non_exhaustive,
     struct_missing,
     struct_must_use_added,
+    struct_now_doc_hidden,
     struct_pub_field_missing,
     struct_repr_c_removed,
     struct_repr_transparent_removed,

test_crates/struct_now_doc_hidden/new/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+publish = false
+name = "struct_now_doc_hidden"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

test_crates/struct_now_doc_hidden/new/src/lib.rs

@@ -0,0 +1,4 @@
+struct StayingKnown;
+
+#[doc(hidden)]
+pub struct Example;

test_crates/struct_now_doc_hidden/old/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+publish = false
+name = "struct_now_doc_hidden"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

test_crates/struct_now_doc_hidden/old/src/lib.rs

@@ -0,0 +1,3 @@
+struct StayingKnown;
+
+pub struct Example;

test_outputs/struct_now_doc_hidden.output.ron

@@ -0,0 +1,46 @@
+{
+    "./test_crates/struct_now_doc_hidden/": [
+        {
+            "path": List([
+                String("struct_now_doc_hidden"),
+                String("Example"),
+            ]),
+            "span_begin_line": Uint64(4),
+            "span_filename": String("src/lib.rs"),
+            "struct_name": String("Example"),
+            "struct_type": String("unit"),
+        },
+    ],
+    "./test_crates/type_hidden_from_public_api/": [
+        {
+            "path": List([
+                String("type_hidden_from_public_api"),
+                String("ExamplePlainStruct"),
+            ]),
+            "span_begin_line": Uint64(2),
+            "span_filename": String("src/lib.rs"),
+            "struct_name": String("ExamplePlainStruct"),
+            "struct_type": String("plain"),
+        },
+        {
+            "path": List([
+                String("type_hidden_from_public_api"),
+                String("ExampleTupleStruct"),
+            ]),
+            "span_begin_line": Uint64(7),
+            "span_filename": String("src/lib.rs"),
+            "struct_name": String("ExampleTupleStruct"),
+            "struct_type": String("tuple"),
+        },
+        {
+            "path": List([
+                String("type_hidden_from_public_api"),
+                String("ExampleUnitStruct"),
+            ]),
+            "span_begin_line": Uint64(10),
+            "span_filename": String("src/lib.rs"),
+            "struct_name": String("ExampleUnitStruct"),
+            "struct_type": String("unit"),
+        },
+    ],
+}