Fix false-positive "macro no longer exported" report.

The old implementation checked that there's a macro with a matching name that isn't exported in the linted code, but didn't check that there is no *exported* macro by that name in the code. This was the cause of issue #1042.

Fixes #1042.

src/lints/declarative_macro_missing.ron

@@ -36,7 +36,7 @@ SemverQuery(
         "zero": 0,
         "true": true,
     },
-    error_message: "A `macro_rules` declarative macro cannot be imported by its prior name. The macro may have been renamed or removed entirely.",
+    error_message: "A `macro_rules` declarative macro cannot be invoked by its prior name. The macro may have been renamed or removed entirely.",
     per_result_error_template:  Some("macro_rules! {{name}}, previously in file {{span_filename}}:{{span_begin_line}}"),
     witness: (
         hint_template: r#"{{name}}!(...);"#

src/lints/macro_no_longer_exported.ron

@@ -13,19 +13,35 @@ SemverQuery(
                     ... on Macro {
                         name @output @tag
                         public_api_eligible @filter(op: "=", value: ["$true"])
+
+                        span_: span @optional {
+                            filename @output
+                            begin_line @output
+                        }
                     }
                 }
             }
             current {
-                item {
+                # There's no exported macro under the name we wanted.
+                item @fold @transform(op: "count") @filter(op: "=", value: ["$zero"]) {
+                    ... on Macro {
+                        name @filter(op: "=", value: ["%name"])
+                        public_api_eligible @filter(op: "=", value: ["$true"])
+                    }
+                }
+
+                # There is at least one macro under the same name that is *not* exported.
+                # Perhaps the macro is not deleted, just no longer exported.
+                item @fold @transform(op: "count") @filter(op: ">", value: ["$zero"]) {
                     ... on Macro {
                         name @filter(op: "=", value: ["%name"])
+
                         # Check the macro still exists but is no longer public API
                         # and isn't doc(hidden) (which would be caught by another lint)
                         public_api_eligible @filter(op: "!=", value: ["$true"])
                         doc_hidden @filter(op: "!=", value: ["$true"])
 
-                        span_: span @optional {
+                        non_exported_span_: span @optional {
                             filename @output
                             begin_line @output
                         }
@@ -36,6 +52,7 @@ SemverQuery(
     }"#,
     arguments: {
         "true": true,
+        "zero": 0,
     },
     error_message: "A macro that was previously exported with #[macro_export] is no longer exported. This breaks downstream code that used the macro.",
     per_result_error_template: Some("macro {{name}} in {{span_filename}}:{{span_begin_line}}"),

test_crates/macro_no_longer_exported/new/src/lib.rs

@@ -20,3 +20,20 @@ macro_rules! internal_macro {
         println!("Internal macro");
     };
 }
+
+pub mod foo {
+    // Private macro, which is not exported despite being in a public module.
+    // Macros require `#[macro_export]` or they aren't visible outside their crate.
+    //
+    // This is a breaking change.
+    macro_rules! some_macro {
+        () => {}
+    }
+}
+
+mod bar {
+    // Private macro by the same name.
+    macro_rules! some_macro {
+        () => {}
+    }
+}

test_crates/macro_no_longer_exported/old/src/lib.rs

@@ -18,3 +18,19 @@ macro_rules! internal_macro {
         println!("Internal macro");
     };
 }
+
+mod foo {
+    // Public macro. Exported even though it's in a private module,
+    // because of the `#[macro_export]`.
+    #[macro_export]
+    macro_rules! some_macro {
+        () => {}
+    }
+}
+
+mod bar {
+    // Private macro by the same name.
+    macro_rules! some_macro {
+        () => {}
+    }
+}

test_outputs/query_execution/macro_no_longer_exported.snap

@@ -7,20 +7,51 @@ snapshot_kind: text
   "./test_crates/declarative_macro_missing/": [
     {
       "name": String("will_no_longer_be_exported"),
-      "span_begin_line": Uint64(1),
+      "non_exported_span_begin_line": List([
+        Uint64(1),
+      ]),
+      "non_exported_span_filename": List([
+        String("src/lib.rs"),
+      ]),
+      "span_begin_line": Uint64(7),
       "span_filename": String("src/lib.rs"),
     },
   ],
   "./test_crates/macro_no_longer_exported/": [
     {
       "name": String("example_macro"),
+      "non_exported_span_begin_line": List([
+        Uint64(2),
+      ]),
+      "non_exported_span_filename": List([
+        String("src/lib.rs"),
+      ]),
       "span_begin_line": Uint64(2),
       "span_filename": String("src/lib.rs"),
     },
+    {
+      "name": String("some_macro"),
+      "non_exported_span_begin_line": List([
+        Uint64(36),
+        Uint64(29),
+      ]),
+      "non_exported_span_filename": List([
+        String("src/lib.rs"),
+        String("src/lib.rs"),
+      ]),
+      "span_begin_line": Uint64(26),
+      "span_filename": String("src/lib.rs"),
+    },
   ],
   "./test_crates/macro_now_doc_hidden/": [
     {
       "name": String("becomes_non_exported"),
+      "non_exported_span_begin_line": List([
+        Uint64(36),
+      ]),
+      "non_exported_span_filename": List([
+        String("src/lib.rs"),
+      ]),
       "span_begin_line": Uint64(36),
       "span_filename": String("src/lib.rs"),
     },

test_outputs/witnesses/macro_no_longer_exported.snap

@@ -6,14 +6,19 @@ snapshot_kind: text
 ---
 [["./test_crates/declarative_macro_missing/"]]
 filename = 'src/lib.rs'
-begin_line = 1
+begin_line = 7
 hint = 'will_no_longer_be_exported!(...);'
 
 [["./test_crates/macro_no_longer_exported/"]]
 filename = 'src/lib.rs'
 begin_line = 2
 hint = 'example_macro!(...);'
 
+[["./test_crates/macro_no_longer_exported/"]]
+filename = 'src/lib.rs'
+begin_line = 26
+hint = 'some_macro!(...);'
+
 [["./test_crates/macro_now_doc_hidden/"]]
 filename = 'src/lib.rs'
 begin_line = 36