[C++] Fix parentheses in macro arguments (#4525)

C++/C++.sublime-syntax

@@ -1148,8 +1148,9 @@ contexts:
       pop: true
     - include: angle-brackets
     - include: types
-    # Allow a macro call
-    - match: '({{identifier}})\s*(\()(?=[^\)]+\))'
+    # Allow a macro call. The lookahead permits up to two levels of nested
+    # parentheses in the macro arguments (e.g. `FOO(a = (b))`).
+    - match: '({{identifier}})\s*(\()(?=(?:[^()]|\((?:[^()]|\([^()]*\))*\))+\))'
       captures:
         1: variable.function.c++
         2: meta.group.c++ punctuation.section.group.begin.c++
@@ -1340,7 +1341,7 @@ contexts:
     - match: ({{macro_identifier}})(?=\s+~?{{identifier}})
       captures:
         1: meta.assumed-macro.c
-    - match: '({{macro_identifier}})\s*(\()(?=[^\)]+\))'
+    - match: '({{macro_identifier}})\s*(\()(?=(?:[^()]|\((?:[^()]|\([^()]*\))*\))+\))'
       captures:
         1: variable.function.c++
         2: meta.group.c++ punctuation.section.group.begin.c++

C++/C.sublime-syntax

@@ -624,8 +624,9 @@ contexts:
       pop: true
     - match: '(?=\s)'
       set: global-maybe-function
-    # Allow a macro call
-    - match: '({{identifier}})\s*(\()(?=[^\)]+\))'
+    # Allow a macro call. The lookahead permits up to two levels of nested
+    # parentheses in the macro arguments (e.g. `FOO(a = (b))`).
+    - match: '({{identifier}})\s*(\()(?=(?:[^()]|\((?:[^()]|\([^()]*\))*\))+\))'
       captures:
         1: variable.function.c
         2: meta.group.c punctuation.section.group.begin.c
@@ -1433,7 +1434,11 @@ contexts:
 
 
   preprocessor-convention-ignore-uppercase-calls-without-semicolon:
-    - match: ^\s*({{macro_identifier}})\s*(\()(?=[^)]*\)\s*$)
+    # The lookahead permits up to two levels of nested parentheses in the
+    # macro arguments (e.g. Unreal Engine's `USTRUCT(meta = (Abstract))`),
+    # so that macros which are the sole content of a line are still
+    # recognised when their arguments contain grouped expressions.
+    - match: ^\s*({{macro_identifier}})\s*(\()(?=(?:[^()]|\((?:[^()]|\([^()]*\))*\))*\)\s*$)
       captures:
         1: variable.function.assumed-macro.c
         2: punctuation.section.group.begin.c

C++/tests/syntax_test_parentheses_in_macro_arguments.h

@@ -0,0 +1,20 @@
+// SYNTAX TEST "Packages/C++/C++.sublime-syntax"
+
+// Test: macros with nested parentheses (e.g. Unreal Engine USTRUCT)
+// should not break highlighting of subsequent struct members.
+
+struct MyPlainStruct
+{
+public:
+// <- storage.modifier.c++
+};
+
+USTRUCT(meta = (Abstract))
+// <- meta.assumed-macro.c variable.function.assumed-macro.c
+struct MyUStruct
+// <- keyword.declaration.struct.type.c++
+//     ^ meta.struct.c++ entity.name.struct.c++
+{
+public:
+// <- storage.modifier.c++
+};