Add lint for "deprecated" attribute on structs and enums

src/lints/struct_deprecated_added.ron

@@ -0,0 +1,60 @@
+SemverQuery(
+    id: "struct_deprecated_added",
+    human_readable_name: "struct #[deprecated] added",
+    description: "A struct has been newly marked with #[deprecated].",
+    required_update: Minor,
+    reference_link: Some("https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-deprecated-attribute"),
+    query: r#"
+    {
+        CrateDiff {
+            current {
+                item {
+                    ... on Struct {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+                        name @output
+
+                        importable_path {
+                            path @tag @output
+                        }
+
+                        attribute {
+                            new_attr: raw_attribute @output
+                            content {
+                                base @filter(op: "=", value: ["$deprecated"])
+                            }
+                        }
+
+                        span_: span @optional {
+                            filename @output
+                            begin_line @output
+                        }
+                    }
+                }
+            }
+            baseline {
+                item {
+                    ... on Struct {
+                        visibility_limit @filter(op: "=", value: ["$public"]) @output
+
+                        importable_path {
+                            path @filter(op: "=", value: ["%path"])
+                        }
+
+                        attribute @fold @transform(op: "count") @filter(op: "=", value: ["$zero"]) {
+                            content {
+                                base @filter(op: "=", value: ["$deprecated"])
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }"#,
+    arguments: {
+        "public": "public",
+        "deprecated": "deprecated",
+        "zero": 0,
+    },
+    error_message: "A struct is now #[deprecated]. Downstream crates will get a compiler warning.",
+    per_result_error_template: Some("struct {{name}} in {{span_filename}}:{{span_begin_line}}"),
+)

src/query.rs

@@ -476,4 +476,5 @@ add_lints!(
     tuple_struct_to_plain_struct,
     unit_struct_changed_kind,
     variant_marked_non_exhaustive,
+    struct_deprecated_added,
 );

test_crates/struct_deprecated_added/new/Cargo.toml

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

test_crates/struct_deprecated_added/new/src/lib.rs

@@ -0,0 +1,59 @@
+// These structs did not have the #[deprecated] attribute in the old version.
+// Addition of the attribute should be reported by this rule.
+
+#[deprecated]
+pub struct StructToDeprecatedStruct {
+    bar: u64,
+}
+
+#[deprecated = "Foo"]
+pub struct StructToDeprecatedMessageStruct {
+    bar: u64,
+}
+
+// These structs had the #[deprecated] attribute in the old version. Changes of
+// the attribute, including deletion, should NOT be reported by this rule.
+
+pub struct DeprecatedStructToStruct {
+    bar: u64,
+}
+
+#[deprecated = "Foo"]
+pub struct DeprecatedStructToDeprecatedMessageStruct {
+    bar: u64,
+}
+
+// These structs had the #[deprecated] attribute in the old version.
+// They also included the user-defined warning message. Changes of
+// the attribute, including deletion, should NOT be reported by this rule.
+
+pub struct DeprecatedMessageStructToStruct {
+    bar: u64,
+}
+
+#[deprecated]
+pub struct DeprecatedMessageStructToDeprecatedStruct {
+    bar: u64,
+}
+
+#[deprecated = "Baz"]
+pub struct DeprecatedMessageStructToDeprecatedMessageStruct {
+    bar: u64,
+}
+
+// This struct is private and should NOT be reported by this rule.
+
+#[deprecated]
+struct DeprecatedPrivateStruct {
+    bar: u64,
+}
+
+// This struct was added in the new version of the crate with its attribute.
+// It should NOT be reported by this rule to avoid duplicate lints.
+// It should be reported as a new pub type that is part of the crate's API.
+// This might seem like a nonsensical test but is a valid edge case.
+
+#[deprecated]
+pub struct DeprecatedNewStruct {
+    bar: u64,
+}

test_crates/struct_deprecated_added/old/Cargo.toml

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

test_crates/struct_deprecated_added/old/src/lib.rs

@@ -0,0 +1,48 @@
+// These structs did not have the #[deprecated] attribute in the old version.
+// Addition of the attribute should be reported by this rule.
+
+pub struct StructToDeprecatedStruct {
+    bar: u64,
+}
+
+pub struct StructToDeprecatedMessageStruct {
+    bar: u64,
+}
+
+// These structs had the #[deprecated] attribute in the old version. Changes of
+// the attribute, including deletion, should NOT be reported by this rule.
+
+#[deprecated]
+pub struct DeprecatedStructToStruct {
+    bar: u64,
+}
+
+#[deprecated]
+pub struct DeprecatedStructToDeprecatedMessageStruct {
+    bar: u64,
+}
+
+// These structs had the #[deprecated] attribute in the old version.
+// They also included the user-defined warning message. Changes of
+// the attribute, including deletion, should NOT be reported by this rule.
+
+#[deprecated = "Foo"]
+pub struct DeprecatedMessageStructToStruct {
+    bar: u64,
+}
+
+#[deprecated = "Foo"]
+pub struct DeprecatedMessageStructToDeprecatedStruct {
+    bar: u64,
+}
+
+#[deprecated = "Foo"]
+pub struct DeprecatedMessageStructToDeprecatedMessageStruct {
+    bar: u64,
+}
+
+// This struct is private and should NOT be reported by this rule.
+
+struct DeprecatedPrivateStruct {
+    bar: u64,
+}

test_outputs/struct_deprecated_added.output.ron

@@ -0,0 +1,26 @@
+{
+    "./test_crates/struct_deprecated_added/": [
+        {
+            "name": String("StructToDeprecatedStruct"),
+            "new_attr": String("#[deprecated]"),
+            "path": List([
+                String("struct_deprecated_added"),
+                String("StructToDeprecatedStruct"),
+            ]),
+            "span_begin_line": Uint64(5),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
+        {
+            "name": String("StructToDeprecatedMessageStruct"),
+            "new_attr": String("#[deprecated = \"Foo\"]"),
+            "path": List([
+                String("struct_deprecated_added"),
+                String("StructToDeprecatedMessageStruct"),
+            ]),
+            "span_begin_line": Uint64(10),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
+    ]
+}