From cf167c9c9c0576472b67f5498a074bc697c9af23 Mon Sep 17 00:00:00 2001
From: Aaron Hill <aa1ronham@gmail.com>
Date: Sat, 24 Jul 2021 17:44:57 -0500
Subject: [PATCH] Only emit lint for local macros

---
 compiler/rustc_expand/src/mbe/macro_rules.rs  | 26 ++++++++++++++-----
 .../auxiliary/foreign-crate.rs                |  4 +++
 .../foreign-crate.rs                          |  9 +++++++
 3 files changed, 32 insertions(+), 7 deletions(-)
 create mode 100644 src/test/ui/lint/semicolon-in-expressions-from-macros/auxiliary/foreign-crate.rs
 create mode 100644 src/test/ui/lint/semicolon-in-expressions-from-macros/foreign-crate.rs

diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index b97593b92b3..9aee86c9e57 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -45,6 +45,8 @@ crate struct ParserAnyMacro<'a> {
     lint_node_id: NodeId,
     is_trailing_mac: bool,
     arm_span: Span,
+    /// Whether or not this macro is defined in the current crate
+    is_local: bool,
 }
 
 crate fn annotate_err_with_kind(
@@ -124,6 +126,7 @@ impl<'a> ParserAnyMacro<'a> {
             lint_node_id,
             arm_span,
             is_trailing_mac,
+            is_local,
         } = *self;
         let snapshot = &mut parser.clone();
         let fragment = match parse_ast_fragment(parser, kind) {
@@ -138,13 +141,15 @@ impl<'a> ParserAnyMacro<'a> {
         // `macro_rules! m { () => { panic!(); } }` isn't parsed by `.parse_expr()`,
         // but `m!()` is allowed in expression positions (cf. issue #34706).
         if kind == AstFragmentKind::Expr && parser.token == token::Semi {
-            parser.sess.buffer_lint_with_diagnostic(
-                SEMICOLON_IN_EXPRESSIONS_FROM_MACROS,
-                parser.token.span,
-                lint_node_id,
-                "trailing semicolon in macro used in expression position",
-                BuiltinLintDiagnostics::TrailingMacro(is_trailing_mac, macro_ident),
-            );
+            if is_local {
+                parser.sess.buffer_lint_with_diagnostic(
+                    SEMICOLON_IN_EXPRESSIONS_FROM_MACROS,
+                    parser.token.span,
+                    lint_node_id,
+                    "trailing semicolon in macro used in expression position",
+                    BuiltinLintDiagnostics::TrailingMacro(is_trailing_mac, macro_ident),
+                );
+            }
             parser.bump();
         }
 
@@ -162,6 +167,7 @@ struct MacroRulesMacroExpander {
     lhses: Vec<mbe::TokenTree>,
     rhses: Vec<mbe::TokenTree>,
     valid: bool,
+    is_local: bool,
 }
 
 impl TTMacroExpander for MacroRulesMacroExpander {
@@ -183,6 +189,7 @@ impl TTMacroExpander for MacroRulesMacroExpander {
             input,
             &self.lhses,
             &self.rhses,
+            self.is_local,
         )
     }
 }
@@ -210,6 +217,7 @@ fn generic_extension<'cx>(
     arg: TokenStream,
     lhses: &[mbe::TokenTree],
     rhses: &[mbe::TokenTree],
+    is_local: bool,
 ) -> Box<dyn MacResult + 'cx> {
     let sess = &cx.sess.parse_sess;
 
@@ -311,6 +319,7 @@ fn generic_extension<'cx>(
                     lint_node_id: cx.current_expansion.lint_node_id,
                     is_trailing_mac: cx.current_expansion.is_trailing_mac,
                     arm_span,
+                    is_local,
                 });
             }
             Failure(token, msg) => match best_failure {
@@ -544,6 +553,9 @@ pub fn compile_declarative_macro(
         lhses,
         rhses,
         valid,
+        // Macros defined in the current crate have a real node id,
+        // whereas macros from an external crate have a dummy id.
+        is_local: def.id != DUMMY_NODE_ID,
     }))
 }
 
diff --git a/src/test/ui/lint/semicolon-in-expressions-from-macros/auxiliary/foreign-crate.rs b/src/test/ui/lint/semicolon-in-expressions-from-macros/auxiliary/foreign-crate.rs
new file mode 100644
index 00000000000..781391cc574
--- /dev/null
+++ b/src/test/ui/lint/semicolon-in-expressions-from-macros/auxiliary/foreign-crate.rs
@@ -0,0 +1,4 @@
+#[macro_export]
+macro_rules! my_macro {
+    () => { true; }
+}
diff --git a/src/test/ui/lint/semicolon-in-expressions-from-macros/foreign-crate.rs b/src/test/ui/lint/semicolon-in-expressions-from-macros/foreign-crate.rs
new file mode 100644
index 00000000000..374506366f8
--- /dev/null
+++ b/src/test/ui/lint/semicolon-in-expressions-from-macros/foreign-crate.rs
@@ -0,0 +1,9 @@
+// aux-build:foreign-crate.rs
+// check-pass
+
+extern crate foreign_crate;
+
+// Test that we do not lint for a macro in a foreign crate
+fn main() {
+    let _ = foreign_crate::my_macro!();
+}