From 3c1b0afcf6eb71ffd543d95cedead3acdedc9e9b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Fournier?= <clement.fournier76@gmail.com>
Date: Wed, 16 Sep 2020 15:40:45 +0200
Subject: [PATCH 1/2] Fix #2783

---
 pmd-java/etc/grammar/Java.jjt                 | 16 ++++++++--
 .../pmd/lang/java/ast/ParserCornersTest.java  |  5 +++
 .../pmd/lang/java/ast/LambdaBug2783.java      | 31 +++++++++++++++++++
 3 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/ast/LambdaBug2783.java

diff --git a/pmd-java/etc/grammar/Java.jjt b/pmd-java/etc/grammar/Java.jjt
index 0962322888..7fc17b1edf 100644
--- a/pmd-java/etc/grammar/Java.jjt
+++ b/pmd-java/etc/grammar/Java.jjt
@@ -1754,11 +1754,23 @@ void UnaryExpressionNotPlusMinus() #UnaryExpressionNotPlusMinus((jjtn000.getImag
  * meaning we can't be explicit as to what can be casted depending on the cast type (primitive or otherwise)
 */
 | LOOKAHEAD("(" (Annotation())* PrimitiveType() ")") CastExpression()
-| LOOKAHEAD("(" (Annotation())* Type() ( "&" ReferenceType() )* ")" UnaryExpressionNotPlusMinus()) CastExpression()
-| PostfixExpression()
+| LOOKAHEAD("(" (Annotation())* Type() ( "&" ReferenceType() )* ")" UnaryExprNotPmStart()) CastExpression()
+| PostfixExpression() // this may be a parenthesized expr, which is why we have lookaheads
 | SwitchExpression()
 }
 
+
+private void UnaryExprNotPmStart() #void:
+{}
+{
+   //  Condensed FIRST set of UnaryExpressionNotPlusMinus
+   //  Avoid looking ahead for a whole UnaryExpressionNotPlusMinus, but just for a token
+
+   "~" | "!" | "(" | "switch" | "new" | "this" | "super" | Literal() | "@"
+   | <IDENTIFIER>
+   | "void" | PrimitiveType()
+}
+
 void PostfixExpression() #PostfixExpression((jjtn000.getImage() != null)):
 {}
 {
diff --git a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/ast/ParserCornersTest.java b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/ast/ParserCornersTest.java
index 4af25e38db..eab5faaaf4 100644
--- a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/ast/ParserCornersTest.java
+++ b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/ast/ParserCornersTest.java
@@ -177,6 +177,11 @@ public class ParserCornersTest {
         java8.parseResource("GitHubBug207.java");
     }
 
+    @Test
+    public void testLambda2783() {
+        java8.parseResource("LambdaBug2783.java");
+    }
+
     @Test
     public void testGitHubBug2767() {
         // PMD fails to parse an initializer block.
diff --git a/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/ast/LambdaBug2783.java b/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/ast/LambdaBug2783.java
new file mode 100644
index 0000000000..425e262c28
--- /dev/null
+++ b/pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/ast/LambdaBug2783.java
@@ -0,0 +1,31 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+import java.util.List;
+
+public class LambdaBug2783 {
+    // https://github.com/pmd/pmd/issues/2783
+
+    public Spec<String> test() {
+        // cast, block body (the failing case)
+        Spec<String> result = (Spec<String>) (a, b) -> {
+            return a.toArray(String[]::new);
+        };
+        // no cast, block body
+        result = (a, b) -> {
+            return a.toArray(String[]::new);
+        };
+        // cast, expression body
+        result = (Spec<String>) (a, b) -> a.toArray(String[]::new);
+
+        // return position?
+        return (Spec<String>) (a, b) -> {
+            return a.toArray(String[]::new);
+        };
+    }
+
+    interface Spec<T> {
+        String[] process(List<T> var1, List<?> var2);
+    }
+}

From d81731ed6c97ab3912a9f8f57d2b1291a1ed6b05 Mon Sep 17 00:00:00 2001
From: Andreas Dangel <andreas.dangel@pmd-code.org>
Date: Thu, 17 Sep 2020 14:57:55 +0200
Subject: [PATCH 2/2] [doc] Update release notes, refs #2784, fixes #2783

---
 docs/pages/release_notes.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/pages/release_notes.md b/docs/pages/release_notes.md
index 5d8124da48..2fa8a74515 100644
--- a/docs/pages/release_notes.md
+++ b/docs/pages/release_notes.md
@@ -35,6 +35,7 @@ AbstractTokenizer and the custom tokenizers of Fortran, Perl and Ruby are deprec
     * [#2756](https://github.com/pmd/pmd/issues/2756): \[java] TypeTestUtil fails with NPE for anonymous class
     * [#2759](https://github.com/pmd/pmd/issues/2759): \[java] False positive in UnusedAssignment
     * [#2767](https://github.com/pmd/pmd/issues/2767): \[java] IndexOutOfBoundsException when parsing an initializer BlockStatement
+    * [#2783](https://github.com/pmd/pmd/issues/2783): \[java] Error while parsing with lambda of custom interface
 
 
 ### API Changes