Fix unused exception in loop

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/ASTCatchStatement.java

@@ -101,4 +101,10 @@ public class ASTCatchStatement extends AbstractJavaNode {
         return getFirstDescendantOfType(ASTVariableDeclaratorId.class).getImage();
     }
 
+    /**
+     * Returns the declarator id for the exception parameter.
+     */
+    public ASTVariableDeclaratorId getExceptionId() {
+        return getFirstChildOfType(ASTFormalParameter.class).getVariableDeclaratorId();
+    }
 }

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/errorprone/UnusedAssignmentRule.java

@@ -108,7 +108,6 @@ public class UnusedAssignmentRule extends AbstractJavaRule {
              or at least proper graph algorithms like toposort)
                 -> this is pretty invisible as it causes false negatives, not FPs
            * test ternary expr
-           * conditional exprs in loops
 
         DONE
            * conditionals
@@ -124,6 +123,7 @@ public class UnusedAssignmentRule extends AbstractJavaRule {
            * test local class/anonymous class
            * shortcut conditionals have their own control-flow
            * parenthesized expressions
+           * conditional exprs in loops
 
      */
 
@@ -543,6 +543,13 @@ public class UnusedAssignmentRule extends AbstractJavaRule {
             return finalState;
         }
 
+        @Override
+        public Object visit(ASTCatchStatement node, Object data) {
+            SpanInfo result = (SpanInfo) visit((JavaNode) node, data);
+            result.deleteVar(node.getExceptionId().getNameDeclaration());
+            return result;
+        }
+
         @Override
         public Object visit(ASTLambdaExpression node, Object data) {
             // Lambda expression have control flow that is separate from the method
@@ -596,7 +603,6 @@ public class UnusedAssignmentRule extends AbstractJavaRule {
                                     JavaNode body,
                                     boolean checkFirstIter,
                                     VariableNameDeclaration foreachVar) {
-            // TODO linkConditional
             final GlobalAlgoState globalState = before.global;
 
             SpanInfo breakTarget = before.forkEmpty();

pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/errorprone/xml/UnusedAssignment.xml

@@ -2509,4 +2509,28 @@ class Foo {
     </test-code>
 
 
+    <test-code>
+        <description>Catch in loop</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+
+            import static unknown.K.*;
+
+            class Foo {
+                {
+                    for (String s : someExpression()) {
+                        try {
+                            foo(s);
+                        } catch (Exception e) {
+                            print("failure");
+                        }
+
+                    }
+                }
+            }
+
+        ]]></code>
+    </test-code>
+
+
 </test-data>