From 819c996ee37ea6f8ea1d17eab34fc3ebfa66bf44 Mon Sep 17 00:00:00 2001
From: Pierluigi Cifani <pcifani@theleftbit.com>
Date: Wed, 4 Nov 2026 11:57:04 +0100
Subject: [PATCH] jextract: skip prefix and postfix operators by their modifier

JavaExtractDecider meant to skip prefix and postfix operators by checking
the name token for .prefixOperator or .postfixOperator. In a declaration
such as `public static prefix func - (value: Number) -> Number` the name is
lexed as a binary operator, and only the `prefix` modifier tells it apart.
So the operator was extracted as a binary operator, and in JNI mode the
Swift thunk printer stopped with `Binary operator must have exactly 2
arguments`. Check the modifiers instead.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 .../JExtractSwiftLib/JavaExtractDecider.swift | 16 +++---
 .../JNI/JNIOperatorsTests.swift               | 56 +++++++++++++++++++
 2 files changed, 63 insertions(+), 9 deletions(-)

diff --git a/Sources/JExtractSwiftLib/JavaExtractDecider.swift b/Sources/JExtractSwiftLib/JavaExtractDecider.swift
index a64ef4466..fefb7cb1f 100644
--- a/Sources/JExtractSwiftLib/JavaExtractDecider.swift
+++ b/Sources/JExtractSwiftLib/JavaExtractDecider.swift
@@ -71,15 +71,13 @@ public struct JavaExtractDecider: ExtractDecider {
       return false
     }
 
-    // Swift operators have no Java mapping
-    if let fn = decl.as(FunctionDeclSyntax.self) {
-      switch fn.name.tokenKind {
-      case .prefixOperator, .postfixOperator:
-        log.trace("Skip '\(decl.qualifiedNameForDebug)': operators are not supported on Java")
-        return false
-      default:
-        break
-      }
+    // Swift prefix and postfix operators have no Java mapping. A declaration's operator name is
+    // lexed as a binary operator, so only the `prefix` or `postfix` modifier tells them apart.
+    if let fn = decl.as(FunctionDeclSyntax.self),
+      fn.modifiers.contains(where: { $0.name.tokenKind == .keyword(.prefix) || $0.name.tokenKind == .keyword(.postfix) })
+    {
+      log.trace("Skip '\(decl.qualifiedNameForDebug)': operators are not supported on Java")
+      return false
     }
 
     guard let mod = decl.asProtocol((any WithModifiersSyntax).self) else {
diff --git a/Tests/JExtractSwiftTests/JNI/JNIOperatorsTests.swift b/Tests/JExtractSwiftTests/JNI/JNIOperatorsTests.swift
index 9863d109d..1eb5d4240 100644
--- a/Tests/JExtractSwiftTests/JNI/JNIOperatorsTests.swift
+++ b/Tests/JExtractSwiftTests/JNI/JNIOperatorsTests.swift
@@ -149,4 +149,60 @@ struct JNIOperatorsTests {
       ]
     )
   }
+
+  let prefixAndPostfixSource =
+    """
+    postfix operator ++
+
+    public struct Number {
+      public static prefix func - (value: Number) -> Number {
+        value
+      }
+
+      public static postfix func ++ (value: Number) -> Number {
+        value
+      }
+
+      public static func + (left: Number, right: Number) -> Number {
+        Number()
+      }
+    }
+    """
+
+  @Test
+  func prefixAndPostfixOperators_areSkipped_javaBindings() throws {
+    try assertOutput(
+      input: prefixAndPostfixSource,
+      .jni,
+      .java,
+      expectedChunks: [
+        """
+        private static native long $plus(long left, long right);
+        """
+      ],
+      notExpectedChunks: [
+        "prefix func",
+        "postfix func",
+      ]
+    )
+  }
+
+  @Test
+  func prefixAndPostfixOperators_areSkipped_swiftThunks() throws {
+    try assertOutput(
+      input: prefixAndPostfixSource,
+      .jni,
+      .swift,
+      detectChunkByInitialLines: 1,
+      expectedChunks: [
+        """
+        @_cdecl("Java_com_example_swift_Number__00024plus__JJ")
+        """
+      ],
+      notExpectedChunks: [
+        "minus",
+        "++",
+      ]
+    )
+  }
 }