New lint: add function_abi_no_longer_unwind lint

src/lints/unwind_function_missing.ron

@@ -0,0 +1,51 @@
+SemverQuery(
+    id: "unwind_function_missing",
+    human_readable_name: "unwind function missing",
+    description: "pub fn changed from an unwind-capable ABI to the same-named ABI without unwind: \"C-unwind\" to \"C\"",
+    required_update: Major,
+    reference_link: None,
+    query: r#"
+    {
+        CrateDiff {
+            baseline {
+                item {
+                    ... on Function {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+
+                        abi_: abi {
+                            name @tag
+                            raw_name @output
+                            unwind @filter(op: "=", value: ["$true"])
+                        }
+                    }
+                }
+            }
+            current {
+                item {
+                    ... on Function {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+
+                        name @output
+
+                        new_abi_: abi {
+                            name @filter(op: "=", value: ["%name"])
+                            raw_name @output
+                            unwind @filter(op: "!=", value: ["$true"])
+                        }
+
+                        span_: span @optional {
+                            filename @output
+                            begin_line @output
+                        }
+                    }
+                }
+            }
+        }
+    }"#,
+    arguments: {
+        "public": "public",
+        "true": true,
+    },
+    error_message: "An unwind-capable ABI changed to same-named ABI without unwind",
+    per_result_error_template: Some("pub fn {{name}} changed ABI from {{abi_raw_name}} to {{new_abi_raw_name}} in {{span_filename}}:{{span_begin_line}}"),
+)

src/query.rs

@@ -534,4 +534,5 @@ add_lints!(
     repr_packed_removed,
     exported_function_changed_abi,
     union_now_doc_hidden,
+    unwind_function_missing,
 );

test_crates/unwind_function_missing/new/Cargo.toml

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

test_crates/unwind_function_missing/new/src/lib.rs

@@ -0,0 +1 @@
+pub extern "C" fn unwind_function_becomes_without_unwind() -> () {}

test_crates/unwind_function_missing/old/Cargo.toml

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

test_crates/unwind_function_missing/old/src/lib.rs

@@ -0,0 +1 @@
+pub extern "C-unwind" fn unwind_function_becomes_without_unwind() -> () {}

test_outputs/unwind_function_missing.output.ron

@@ -0,0 +1,11 @@
+{
+    "./test_crates/unwind_function_missing/": [
+        {
+            "abi_raw_name": String("C-unwind"),
+            "name": String("unwind_function_becomes_without_unwind"),
+            "new_abi_raw_name": String("C"),
+            "span_begin_line": Uint64(1),
+            "span_filename": String("src/lib.rs"),
+        },
+    ],
+}