Add enum_no_longer_non_exhaustive lint.

src/lints/enum_unmarked_non_exhaustive.ron

@@ -0,0 +1,52 @@
+SemverQuery(
+    id: "enum_unmarked_non_exhaustive",
+    human_readable_name: "enum unmarked #[non_exhaustive]",
+    description: "A Public API enum is no longer #[non_exhaustive]",
+    required_update: Minor,
+    lint_level: Allow,
+    reference_link: Some("https://doc.rust-lang.org/reference/attributes/type_system.html#the-non_exhaustive-attribute"),
+    query: r#"
+    {
+        CrateDiff {
+            current {
+                item {
+                    ... on Enum {
+                        visibility_limit @filter(op: "=", value: ["$public"]) @output
+                        name @output @tag
+
+                        attrs @filter(op: "not_contains", value: ["$non_exhaustive"])
+
+                        importable_path {
+                            path @output @tag
+                        }
+
+                        span_: span @optional {
+                            filename @output
+                            begin_line @output
+                        }
+                    }
+                }
+            }
+            baseline {
+                item {
+                    ... on Enum {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+                        name @filter(op: "=", value: ["%name"])
+
+                        attrs @filter(op: "contains", value: ["$non_exhaustive"])
+
+                        importable_path {
+                            path @filter(op: "=", value: ["%path"])
+                        }
+                    }
+                }
+            }
+        }
+    }"#,
+    arguments: {
+        "public": "public",
+        "non_exhaustive": "#[non_exhaustive]",
+    },
+    error_message: "A Public API enum is no longer #[non_exhaustive]. External code may assume all variants are known, causing breaking changes if new ones are added.",
+    per_result_error_template: Some("enum {{name}} in {{span_filename}}:{{span_begin_line}}"),
+)

src/query.rs

@@ -1246,6 +1246,7 @@ add_lints!(
     enum_tuple_variant_field_missing,
     enum_tuple_variant_field_now_doc_hidden,
     enum_unit_variant_changed_kind,
+    enum_unmarked_non_exhaustive,
     enum_variant_added,
     enum_variant_marked_deprecated,
     enum_variant_marked_non_exhaustive,

test_crates/enum_unmarked_non_exhaustive/new/Cargo.toml

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

test_crates/enum_unmarked_non_exhaustive/new/src/lib.rs

@@ -0,0 +1,6 @@
+#![no_std]
+
+pub enum SimpleEnum {
+    VariantA,
+    VariantB,
+}

test_crates/enum_unmarked_non_exhaustive/old/Cargo.toml

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

test_crates/enum_unmarked_non_exhaustive/old/src/lib.rs

@@ -0,0 +1,7 @@
+#![no_std]
+
+#[non_exhaustive]
+pub enum SimpleEnum {
+    VariantA,
+    VariantB,
+}

test_outputs/query_execution/enum_unmarked_non_exhaustive.snap

@@ -0,0 +1,42 @@
+---
+source: src/query.rs
+expression: "&query_execution_results"
+---
+{
+  "./test_crates/enum_repr_variant_discriminant_changed/": [
+    {
+      "name": String("DiscriminantIsChangedButAVariantIsNonExhaustive"),
+      "path": List([
+        String("enum_repr_variant_discriminant_changed"),
+        String("DiscriminantIsChangedButAVariantIsNonExhaustive"),
+      ]),
+      "span_begin_line": Uint64(23),
+      "span_filename": String("src/lib.rs"),
+      "visibility_limit": String("public"),
+    },
+  ],
+  "./test_crates/enum_unmarked_non_exhaustive/": [
+    {
+      "name": String("SimpleEnum"),
+      "path": List([
+        String("enum_unmarked_non_exhaustive"),
+        String("SimpleEnum"),
+      ]),
+      "span_begin_line": Uint64(3),
+      "span_filename": String("src/lib.rs"),
+      "visibility_limit": String("public"),
+    },
+  ],
+  "./test_crates/type_mismatched_generic_lifetimes/": [
+    {
+      "name": String("Either"),
+      "path": List([
+        String("type_mismatched_generic_lifetimes"),
+        String("Either"),
+      ]),
+      "span_begin_line": Uint64(7),
+      "span_filename": String("src/lib.rs"),
+      "visibility_limit": String("public"),
+    },
+  ],
+}