Auto merge of #13988 - dsprenkels:tidy-fncalls, r=Wafflespeanut

test-tidy: Check for space between function name and `(`

<!-- Please describe your changes on the following line: -->

Disallow an extraneous space in a function call between
the function name and the opening parenthesis in Rust
code, while ignoring macro declarations.

---

<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy --all` does not report any errors
- [x] `./mach test-tidy --self` does not report any errors
- [x] These changes fix #13980

<!-- Either: -->
- [x] There are tests for these changes, these are written in
 - `python/tidy/servo_tidy_tests/rust_tidy.rs`
 - `python/tidy/servo_tidy_tests/test_tidy.py`
- [ ] These changes do not require tests

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

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3 files changed, 11 insertions, 1 deletions

diff --git a/python/tidy/servo_tidy/tidy.py b/python/tidy/servo_tidy/tidy.py
index a8e53d7804e..b0e420988d7 100644
--- a/python/tidy/servo_tidy/tidy.py
+++ b/python/tidy/servo_tidy/tidy.py
@@ -442,6 +442,13 @@ def check_rust(file_name, lines):
         regex_rules = [
             (r",[^\s]", "missing space after ,",
                 lambda match, line: '$' not in line and not is_attribute),
+            (r"([A-Za-z0-9_]+) (\()", "extra space after {0}",
+                lambda match, line: not (
+                    is_attribute or
+                    re.match(r"\bmacro_rules!\s+", line[:match.start()]) or
+                    re.search(r"[^']'[A-Za-z0-9_]+ \($", line[:match.end()]) or
+                    match.group(1) in ['const', 'fn', 'for', 'if', 'in',
+                                       'let', 'match', 'mut', 'return'])),
             (r"[A-Za-z0-9\"]=", "missing space before =",
                 lambda match, line: is_attribute),
             (r"=[A-Za-z0-9\"]", "missing space after =",
diff --git a/python/tidy/servo_tidy_tests/rust_tidy.rs b/python/tidy/servo_tidy_tests/rust_tidy.rs
index 358fce3a082..79be0ff1580 100644
--- a/python/tidy/servo_tidy_tests/rust_tidy.rs
+++ b/python/tidy/servo_tidy_tests/rust_tidy.rs
@@ -52,7 +52,9 @@ impl test {
     type Text_Fun3 = fn( i32) -> i32;
 
     fn test_fun3<Text_Fun3>( y: Text_Fun3) {
-        test_fun( 1);
+        let (x, y) = (1, 2) // Should not trigger
+        test_fun( x);
+        test_fun (y);
     }
 
     // Should not be triggered
diff --git a/python/tidy/servo_tidy_tests/test_tidy.py b/python/tidy/servo_tidy_tests/test_tidy.py
index dca0c5765b1..7bec2c61718 100644
--- a/python/tidy/servo_tidy_tests/test_tidy.py
+++ b/python/tidy/servo_tidy_tests/test_tidy.py
@@ -124,6 +124,7 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('extra space after (', errors.next()[2])
         self.assertEqual('extra space after (', errors.next()[2])
         self.assertEqual('extra space after (', errors.next()[2])
+        self.assertEqual('extra space after test_fun', errors.next()[2])
         self.assertNoMoreErrors(errors)
 
     def test_spec_link(self):