Fix unused_parens triggers on macro by example code

src/librustc_lint/unused.rs

@@ -355,7 +355,9 @@ impl UnusedParens {
         match value.kind {
             ast::ExprKind::Paren(ref inner) => {
                 if !Self::is_expr_parens_necessary(inner, followed_by_block) &&
-                    value.attrs.is_empty() {
+                    value.attrs.is_empty() &&
+                    !value.span.from_expansion()
+                {
                     let expr_text = if let Ok(snippet) = cx.sess().source_map()
                         .span_to_snippet(value.span) {
                             snippet

src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs

@@ -17,10 +17,7 @@ macro_rules! the_worship_the_heart_lifts_above {
 
 macro_rules! and_the_heavens_reject_not {
     () => {
-        // ↓ But let's test that we still lint for unused parens around
-        // function args inside of simple, one-deep macros.
         #[allow(dead_code)] fn the_night_for_the_morrow() -> Option<isize> { Some((2)) }
-        //~^ WARN unnecessary parentheses around function argument
     }
 }
 

src/test/ui/lint/lint-unnecessary-parens.rs

@@ -25,6 +25,12 @@ fn passes_unused_parens_lint() -> &'static (dyn Trait) {
     panic!()
 }
 
+macro_rules! baz {
+    ($($foo:expr),+) => {
+        ($($foo),*)
+    }
+}
+
 fn main() {
     foo();
     bar((true)); //~ ERROR unnecessary parentheses around function argument
@@ -55,4 +61,7 @@ fn main() {
     let mut _a = (0); //~ ERROR unnecessary parentheses around assigned value
     _a = (0); //~ ERROR unnecessary parentheses around assigned value
     _a += (1); //~ ERROR unnecessary parentheses around assigned value
+
+    let _a = baz!(3, 4);
+    let _b = baz!(3);
 }

src/test/ui/lint/lint-unnecessary-parens.stderr

@@ -23,69 +23,69 @@ LL | fn unused_parens_around_return_type() -> (u32) {
    |                                          ^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around function argument
-  --> $DIR/lint-unnecessary-parens.rs:30:9
+  --> $DIR/lint-unnecessary-parens.rs:36:9
    |
 LL |     bar((true));
    |         ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around `if` condition
-  --> $DIR/lint-unnecessary-parens.rs:32:8
+  --> $DIR/lint-unnecessary-parens.rs:38:8
    |
 LL |     if (true) {}
    |        ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around `while` condition
-  --> $DIR/lint-unnecessary-parens.rs:33:11
+  --> $DIR/lint-unnecessary-parens.rs:39:11
    |
 LL |     while (true) {}
    |           ^^^^^^ help: remove these parentheses
 
 warning: denote infinite loops with `loop { ... }`
-  --> $DIR/lint-unnecessary-parens.rs:33:5
+  --> $DIR/lint-unnecessary-parens.rs:39:5
    |
 LL |     while (true) {}
    |     ^^^^^^^^^^^^ help: use `loop`
    |
    = note: `#[warn(while_true)]` on by default
 
 error: unnecessary parentheses around `match` head expression
-  --> $DIR/lint-unnecessary-parens.rs:35:11
+  --> $DIR/lint-unnecessary-parens.rs:41:11
    |
 LL |     match (true) {
    |           ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around `let` head expression
-  --> $DIR/lint-unnecessary-parens.rs:38:16
+  --> $DIR/lint-unnecessary-parens.rs:44:16
    |
 LL |     if let 1 = (1) {}
    |                ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around `let` head expression
-  --> $DIR/lint-unnecessary-parens.rs:39:19
+  --> $DIR/lint-unnecessary-parens.rs:45:19
    |
 LL |     while let 1 = (2) {}
    |                   ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around method argument
-  --> $DIR/lint-unnecessary-parens.rs:53:24
+  --> $DIR/lint-unnecessary-parens.rs:59:24
    |
 LL |     X { y: false }.foo((true));
    |                        ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:55:18
+  --> $DIR/lint-unnecessary-parens.rs:61:18
    |
 LL |     let mut _a = (0);
    |                  ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:56:10
+  --> $DIR/lint-unnecessary-parens.rs:62:10
    |
 LL |     _a = (0);
    |          ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:57:11
+  --> $DIR/lint-unnecessary-parens.rs:63:11
    |
 LL |     _a += (1);
    |           ^^^ help: remove these parentheses