diff --git a/pmd-core/src/main/java/net/sourceforge/pmd/lang/metrics/MetricKeyUtil.java b/pmd-core/src/main/java/net/sourceforge/pmd/lang/metrics/MetricKeyUtil.java
index d5391b3ae0..4388489784 100644
--- a/pmd-core/src/main/java/net/sourceforge/pmd/lang/metrics/MetricKeyUtil.java
+++ b/pmd-core/src/main/java/net/sourceforge/pmd/lang/metrics/MetricKeyUtil.java
@@ -22,7 +22,7 @@ public class MetricKeyUtil {
 
 
     /**
-     * Creates a new metric key holding a metric which can be computed on a class.
+     * Creates a new metric key from its metric and name.
      *
      * @param name   The name of the metric
      * @param metric The metric to use
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetrics.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetrics.java
index 607703b590..dd1134bcd2 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetrics.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetrics.java
@@ -6,7 +6,7 @@ package net.sourceforge.pmd.lang.java.metrics;
 
 
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.metrics.MetricKey;
 import net.sourceforge.pmd.lang.metrics.MetricOptions;
 import net.sourceforge.pmd.lang.metrics.ResultOption;
@@ -79,7 +79,7 @@ public final class JavaMetrics {
      *
      * @return The value of the metric, or {@code Double.NaN} if the value couldn't be computed
      */
-    public static double get(MetricKey<ASTMethodOrConstructorDeclaration> key, ASTMethodOrConstructorDeclaration node) {
+    public static double get(MetricKey<MethodLike> key, MethodLike node) {
         return FACADE.computeForOperation(key, node, MetricOptions.emptyOptions());
     }
 
@@ -93,8 +93,7 @@ public final class JavaMetrics {
      *
      * @return The value of the metric, or {@code Double.NaN} if the value couldn't be computed
      */
-    public static double get(MetricKey<ASTMethodOrConstructorDeclaration> key, ASTMethodOrConstructorDeclaration node,
-                             MetricOptions options) {
+    public static double get(MetricKey<MethodLike> key, MethodLike node, MetricOptions options) {
         return FACADE.computeForOperation(key, node, options);
     }
 
@@ -107,10 +106,9 @@ public final class JavaMetrics {
      * @param node         The node on which to compute the metric
      * @param resultOption The result option to use
      *
-     * @return The value of the metric, or {@code Double.NaN} if the value couldn't be computed or {@code option} is
-     * {@code null}
+     * @return The value of the metric, or {@code Double.NaN} if the value couldn't be computed
      */
-    public static double get(MetricKey<ASTMethodOrConstructorDeclaration> key, ASTAnyTypeDeclaration node, ResultOption resultOption) {
+    public static double get(MetricKey<MethodLike> key, ASTAnyTypeDeclaration node, ResultOption resultOption) {
         return FACADE.computeWithResultOption(key, node, MetricOptions.emptyOptions(), resultOption);
     }
 
@@ -124,10 +122,9 @@ public final class JavaMetrics {
      * @param resultOption The result option to use
      * @param options      The version of the metric
      *
-     * @return The value of the metric, or {@code Double.NaN} if the value couldn't be computed or {@code option} is
-     * {@code null}
+     * @return The value of the metric, or {@code Double.NaN} if the value couldn't be computed
      */
-    public static double get(MetricKey<ASTMethodOrConstructorDeclaration> key, ASTAnyTypeDeclaration node,
+    public static double get(MetricKey<MethodLike> key, ASTAnyTypeDeclaration node,
                              MetricOptions options, ResultOption resultOption) {
         return FACADE.computeWithResultOption(key, node, options, resultOption);
     }
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetricsComputer.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetricsComputer.java
index 63287a7d8a..2c989762b7 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetricsComputer.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetricsComputer.java
@@ -10,6 +10,7 @@ import java.util.List;
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeBodyDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.metrics.AbstractMetricsComputer;
 
 /**
@@ -17,7 +18,7 @@ import net.sourceforge.pmd.lang.metrics.AbstractMetricsComputer;
  *
  * @author Clément Fournier
  */
-public class JavaMetricsComputer extends AbstractMetricsComputer<ASTAnyTypeDeclaration, ASTMethodOrConstructorDeclaration> {
+public class JavaMetricsComputer extends AbstractMetricsComputer<ASTAnyTypeDeclaration, MethodLike> {
 
     static final JavaMetricsComputer INSTANCE = new JavaMetricsComputer();
 
@@ -26,11 +27,11 @@ public class JavaMetricsComputer extends AbstractMetricsComputer<ASTAnyTypeDecla
 
     }
 
-
+    // TODO: doesn't consider lambdas
     @Override
-    protected List<ASTMethodOrConstructorDeclaration> findOperations(ASTAnyTypeDeclaration node) {
+    protected List<MethodLike> findOperations(ASTAnyTypeDeclaration node) {
 
-        List<ASTMethodOrConstructorDeclaration> operations = new ArrayList<>();
+        List<MethodLike> operations = new ArrayList<>();
 
         for (ASTAnyTypeBodyDeclaration decl : node.getDeclarations()) {
             if (decl.jjtGetNumChildren() > 0 && decl.jjtGetChild(0) instanceof ASTMethodOrConstructorDeclaration) {
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetricsFacade.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetricsFacade.java
index 26cf94d683..129d7b3840 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetricsFacade.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaMetricsFacade.java
@@ -5,7 +5,7 @@
 package net.sourceforge.pmd.lang.java.metrics;
 
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.metrics.AbstractMetricsFacade;
 import net.sourceforge.pmd.lang.metrics.MetricsComputer;
 
@@ -14,7 +14,7 @@ import net.sourceforge.pmd.lang.metrics.MetricsComputer;
  *
  * @author Clément Fournier
  */
-class JavaMetricsFacade extends AbstractMetricsFacade<ASTAnyTypeDeclaration, ASTMethodOrConstructorDeclaration> {
+class JavaMetricsFacade extends AbstractMetricsFacade<ASTAnyTypeDeclaration, MethodLike> {
 
     private final JavaProjectMemoizer memoizer = new JavaProjectMemoizer();
 
@@ -32,7 +32,7 @@ class JavaMetricsFacade extends AbstractMetricsFacade<ASTAnyTypeDeclaration, AST
 
 
     @Override
-    protected MetricsComputer<ASTAnyTypeDeclaration, ASTMethodOrConstructorDeclaration> getLanguageSpecificComputer() {
+    protected MetricsComputer<ASTAnyTypeDeclaration, MethodLike> getLanguageSpecificComputer() {
         return JavaMetricsComputer.INSTANCE;
     }
 
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaProjectMemoizer.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaProjectMemoizer.java
index c85c1a2f92..f7159e1d65 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaProjectMemoizer.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/JavaProjectMemoizer.java
@@ -5,7 +5,7 @@
 package net.sourceforge.pmd.lang.java.metrics;
 
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.metrics.BasicProjectMemoizer;
 
 /**
@@ -13,6 +13,6 @@ import net.sourceforge.pmd.lang.metrics.BasicProjectMemoizer;
  *
  * @author Clément Fournier
  */
-class JavaProjectMemoizer extends BasicProjectMemoizer<ASTAnyTypeDeclaration, ASTMethodOrConstructorDeclaration> {
+class JavaProjectMemoizer extends BasicProjectMemoizer<ASTAnyTypeDeclaration, MethodLike> {
 
 }
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/api/JavaOperationMetric.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/api/JavaOperationMetric.java
index 2026085579..e52e22e70f 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/api/JavaOperationMetric.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/api/JavaOperationMetric.java
@@ -4,7 +4,7 @@
 
 package net.sourceforge.pmd.lang.java.metrics.api;
 
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.metrics.Metric;
 
 /**
@@ -12,7 +12,7 @@ import net.sourceforge.pmd.lang.metrics.Metric;
  *
  * @author Clément Fournier
  */
-public interface JavaOperationMetric extends Metric<ASTMethodOrConstructorDeclaration> {
+public interface JavaOperationMetric extends Metric<MethodLike> {
 
 
 }
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/api/JavaOperationMetricKey.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/api/JavaOperationMetricKey.java
index 152a3bf4d9..aa61895551 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/api/JavaOperationMetricKey.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/api/JavaOperationMetricKey.java
@@ -4,7 +4,7 @@
 
 package net.sourceforge.pmd.lang.java.metrics.api;
 
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.impl.AtfdMetric.AtfdOperationMetric;
 import net.sourceforge.pmd.lang.java.metrics.impl.CycloMetric;
 import net.sourceforge.pmd.lang.java.metrics.impl.LocMetric.LocOperationMetric;
@@ -12,10 +12,11 @@ import net.sourceforge.pmd.lang.java.metrics.impl.NcssMetric.NcssOperationMetric
 import net.sourceforge.pmd.lang.java.metrics.impl.NpathMetric;
 import net.sourceforge.pmd.lang.metrics.MetricKey;
 
+
 /**
  * Keys identifying standard operation metrics.
  */
-public enum JavaOperationMetricKey implements MetricKey<ASTMethodOrConstructorDeclaration> {
+public enum JavaOperationMetricKey implements MetricKey<MethodLike> {
 
     /**
      * Access to Foreign Data.
@@ -69,9 +70,7 @@ public enum JavaOperationMetricKey implements MetricKey<ASTMethodOrConstructorDe
 
 
     @Override
-    public boolean supports(ASTMethodOrConstructorDeclaration node) {
+    public boolean supports(MethodLike node) {
         return calculator.supports(node);
     }
-
-
 }
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/AbstractJavaOperationMetric.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/AbstractJavaOperationMetric.java
index 90403d55e0..8b1220d585 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/AbstractJavaOperationMetric.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/AbstractJavaOperationMetric.java
@@ -4,17 +4,19 @@
 
 package net.sourceforge.pmd.lang.java.metrics.impl;
 
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.AbstractJavaMetric;
 import net.sourceforge.pmd.lang.java.metrics.api.JavaOperationMetric;
 
+
 /**
- * Base class for operation metrics.
+ * Base class for operation metrics. Can be applied on method and constructor declarations, and
+ * lambda expressions.
  *
  * @author Clément Fournier
  */
-public abstract class AbstractJavaOperationMetric extends AbstractJavaMetric<ASTMethodOrConstructorDeclaration>
-    implements JavaOperationMetric {
+public abstract class AbstractJavaOperationMetric extends AbstractJavaMetric<MethodLike>
+        implements JavaOperationMetric {
 
     /**
      * Returns true if the metric can be computed on this operation. By default, abstract operations are filtered out.
@@ -23,7 +25,7 @@ public abstract class AbstractJavaOperationMetric extends AbstractJavaMetric<AST
      *
      * @return True if the metric can be computed on this operation
      */
-    public boolean supports(ASTMethodOrConstructorDeclaration node) {
+    public boolean supports(MethodLike node) {
         return !node.isAbstract();
     }
 }
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/AtfdMetric.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/AtfdMetric.java
index 01add07369..717b530759 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/AtfdMetric.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/AtfdMetric.java
@@ -8,7 +8,7 @@ import org.apache.commons.lang3.mutable.MutableInt;
 
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTMethodDeclaration;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.JavaMetrics;
 import net.sourceforge.pmd.lang.java.metrics.api.JavaOperationMetricKey;
 import net.sourceforge.pmd.lang.java.metrics.impl.visitors.AtfdBaseVisitor;
@@ -27,13 +27,13 @@ public final class AtfdMetric {
     public static final class AtfdOperationMetric extends AbstractJavaOperationMetric {
 
         @Override
-        public boolean supports(ASTMethodOrConstructorDeclaration node) {
+        public boolean supports(MethodLike node) {
             return node instanceof ASTMethodDeclaration && super.supports(node);
         }
 
 
         @Override
-        public double computeFor(ASTMethodOrConstructorDeclaration node, MetricOptions options) {
+        public double computeFor(MethodLike node, MetricOptions options) {
             return ((MutableInt) node.jjtAccept(new AtfdBaseVisitor(), new MutableInt(0))).getValue();
         }
 
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/CycloMetric.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/CycloMetric.java
index 6d7fd24692..071cfbe1d6 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/CycloMetric.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/CycloMetric.java
@@ -12,8 +12,8 @@ import org.apache.commons.lang3.mutable.MutableInt;
 import net.sourceforge.pmd.lang.java.ast.ASTConditionalAndExpression;
 import net.sourceforge.pmd.lang.java.ast.ASTConditionalOrExpression;
 import net.sourceforge.pmd.lang.java.ast.ASTExpression;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
 import net.sourceforge.pmd.lang.java.ast.JavaParserDecoratedVisitor;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.impl.visitors.CycloAssertAwareDecorator;
 import net.sourceforge.pmd.lang.java.metrics.impl.visitors.CycloBaseVisitor;
 import net.sourceforge.pmd.lang.java.metrics.impl.visitors.CycloPathAwareDecorator;
@@ -34,7 +34,7 @@ public final class CycloMetric extends AbstractJavaOperationMetric {
 
 
     @Override
-    public double computeFor(ASTMethodOrConstructorDeclaration node, MetricOptions options) {
+    public double computeFor(final MethodLike node, MetricOptions options) {
         Set<MetricOption> opts = options.getOptions();
         JavaParserDecoratedVisitor visitor = new JavaParserDecoratedVisitor(CycloBaseVisitor.INSTANCE);
 
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/LocMetric.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/LocMetric.java
index 79324a9ed9..f39ab4d426 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/LocMetric.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/LocMetric.java
@@ -5,7 +5,7 @@
 package net.sourceforge.pmd.lang.java.metrics.impl;
 
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.metrics.MetricOptions;
 
 /**
@@ -21,13 +21,13 @@ public final class LocMetric {
     public static final class LocOperationMetric extends AbstractJavaOperationMetric {
 
         @Override
-        public boolean supports(ASTMethodOrConstructorDeclaration node) {
+        public boolean supports(MethodLike node) {
             return true;
         }
 
 
         @Override
-        public double computeFor(ASTMethodOrConstructorDeclaration node, MetricOptions options) {
+        public double computeFor(MethodLike node, MetricOptions options) {
             return 1 + node.getEndLine() - node.getBeginLine();
         }
     }
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/NcssMetric.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/NcssMetric.java
index 841a4e0c1d..cb141bb8f5 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/NcssMetric.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/NcssMetric.java
@@ -9,8 +9,8 @@ import java.util.Set;
 import org.apache.commons.lang3.mutable.MutableInt;
 
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
 import net.sourceforge.pmd.lang.java.ast.JavaParserDecoratedVisitor;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.impl.visitors.NcssBaseVisitor;
 import net.sourceforge.pmd.lang.java.metrics.impl.visitors.NcssCountImportsDecorator;
 import net.sourceforge.pmd.lang.metrics.MetricOption;
@@ -73,13 +73,13 @@ public final class NcssMetric {
     public static final class NcssOperationMetric extends AbstractJavaOperationMetric {
 
         @Override
-        public boolean supports(ASTMethodOrConstructorDeclaration node) {
+        public boolean supports(MethodLike node) {
             return true;
         }
 
 
         @Override
-        public double computeFor(ASTMethodOrConstructorDeclaration node, MetricOptions version) {
+        public double computeFor(MethodLike node, MetricOptions version) {
             Set<MetricOption> options = version.getOptions();
             JavaParserDecoratedVisitor visitor = new JavaParserDecoratedVisitor(NcssBaseVisitor.INSTANCE);
 
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/NpathMetric.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/NpathMetric.java
index 634fcc6e26..7a21477337 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/NpathMetric.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/impl/NpathMetric.java
@@ -5,7 +5,7 @@
 package net.sourceforge.pmd.lang.java.metrics.impl;
 
 
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.impl.visitors.NpathBaseVisitor;
 import net.sourceforge.pmd.lang.metrics.MetricOptions;
 
@@ -18,7 +18,7 @@ import net.sourceforge.pmd.lang.metrics.MetricOptions;
 public class NpathMetric extends AbstractJavaOperationMetric {
 
     @Override
-    public double computeFor(ASTMethodOrConstructorDeclaration node, MetricOptions options) {
+    public double computeFor(MethodLike node, MetricOptions options) {
         return (Integer) node.jjtAccept(NpathBaseVisitor.INSTANCE, null);
     }
 
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/AbstractJavaMetricsRule.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/AbstractJavaMetricsRule.java
index 45c84d2241..7ff5166c71 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/AbstractJavaMetricsRule.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/rule/AbstractJavaMetricsRule.java
@@ -9,9 +9,12 @@ import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTClassOrInterfaceDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTConstructorDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTEnumDeclaration;
+import net.sourceforge.pmd.lang.java.ast.ASTLambdaExpression;
 import net.sourceforge.pmd.lang.java.ast.ASTMethodDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
 import net.sourceforge.pmd.lang.java.ast.JavaNode;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
+
 
 /**
  * Java Rule with convenient visit methods to e.g. treat contructors and methods the same.
@@ -54,10 +57,19 @@ public abstract class AbstractJavaMetricsRule extends AbstractJavaRule {
         return visit((ASTMethodOrConstructorDeclaration) node, data);
     }
 
-
-    public Object visit(ASTMethodOrConstructorDeclaration node, Object data) {
-        return visit((JavaNode) node, data);
+    @Override
+    public final Object visit(ASTLambdaExpression node, Object data) {
+        return visit((MethodLike) node, data);
     }
 
 
+    public Object visit(ASTMethodOrConstructorDeclaration node, Object data) {
+        return visit((MethodLike) node, data);
+    }
+
+
+    public Object visit(MethodLike node, Object data) {
+        return visit((JavaNode) node, data);
+    }
+
 }
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/xpath/MetricFunction.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/xpath/MetricFunction.java
index d53d88bb87..ffc12e888c 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/xpath/MetricFunction.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/xpath/MetricFunction.java
@@ -10,18 +10,23 @@ import java.util.Map;
 import org.apache.commons.lang3.EnumUtils;
 import org.jaxen.Context;
 import org.jaxen.Function;
-import org.jaxen.FunctionCallException;
 import org.jaxen.SimpleFunctionContext;
 import org.jaxen.XPathFunctionContext;
 
 import net.sourceforge.pmd.lang.ast.Node;
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.JavaMetrics;
 import net.sourceforge.pmd.lang.java.metrics.api.JavaClassMetricKey;
 import net.sourceforge.pmd.lang.java.metrics.api.JavaOperationMetricKey;
 
+
 /**
+ * Implements the {@code metric()} XPath function. Takes the
+ * string name of a metric and the context node and returns
+ * the result if the metric can be computed, otherwise returns
+ * {@link Double#NaN}.
+ *
  * @author Clément Fournier
  * @since 6.0.0
  */
@@ -33,9 +38,7 @@ public class MetricFunction implements Function {
 
 
     @Override
-    public Object call(Context context, List args) throws FunctionCallException {
-
-        String metricKeyName = null;
+    public Object call(Context context, List args) {
 
         if (args.size() == 0) {
             throw new IllegalArgumentException(badMetricKeyArgMessage());
@@ -45,9 +48,9 @@ public class MetricFunction implements Function {
             throw new IllegalArgumentException(badMetricKeyArgMessage());
         }
 
-        metricKeyName = (String) args.get(0);
-
+        String metricKeyName = (String) args.get(0);
         Node n = (Node) context.getNodeSet().get(0);
+
         return getMetric(n, metricKeyName);
     }
 
@@ -75,8 +78,8 @@ public class MetricFunction implements Function {
     public static double getMetric(Node n, String metricKeyName) {
         if (n instanceof ASTAnyTypeDeclaration) {
             return getClassMetric((ASTAnyTypeDeclaration) n, getClassMetricKey(metricKeyName));
-        } else if (n instanceof ASTMethodOrConstructorDeclaration) {
-            return getOpMetric((ASTMethodOrConstructorDeclaration) n, getOperationMetricKey(metricKeyName));
+        } else if (n instanceof MethodLike) {
+            return getOpMetric((MethodLike) n, getOperationMetricKey(metricKeyName));
         } else {
             throw new IllegalStateException(genericBadNodeMessage());
         }
@@ -101,7 +104,7 @@ public class MetricFunction implements Function {
     }
 
 
-    private static double getOpMetric(ASTMethodOrConstructorDeclaration node, JavaOperationMetricKey key) {
+    private static double getOpMetric(MethodLike node, JavaOperationMetricKey key) {
         return JavaMetrics.get(key, node);
     }
 
diff --git a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ProjectMemoizerTest.java b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ProjectMemoizerTest.java
index 49a0a41267..c005465b36 100644
--- a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ProjectMemoizerTest.java
+++ b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ProjectMemoizerTest.java
@@ -19,6 +19,7 @@ import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTCompilationUnit;
 import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
 import net.sourceforge.pmd.lang.java.ast.JavaParserVisitorReducedAdapter;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.impl.AbstractJavaClassMetric;
 import net.sourceforge.pmd.lang.java.metrics.impl.AbstractJavaOperationMetric;
 import net.sourceforge.pmd.lang.java.metrics.testdata.MetricsVisitorTestData;
@@ -33,7 +34,7 @@ import net.sourceforge.pmd.lang.metrics.MetricOptions;
 public class ProjectMemoizerTest {
 
     private MetricKey<ASTAnyTypeDeclaration> classMetricKey = MetricKeyUtil.of(null, new RandomClassMetric());
-    private MetricKey<ASTMethodOrConstructorDeclaration> opMetricKey = MetricKeyUtil.of(null, new RandomOperationMetric());
+    private MetricKey<MethodLike> opMetricKey = MetricKeyUtil.of(null, new RandomOperationMetric());
 
 
     @Test
@@ -72,7 +73,7 @@ public class ProjectMemoizerTest {
         acu.jjtAccept(new JavaParserVisitorReducedAdapter() {
             @Override
             public Object visit(ASTMethodOrConstructorDeclaration node, Object data) {
-                MetricMemoizer<ASTMethodOrConstructorDeclaration> op = toplevel.getOperationMemoizer(node.getQualifiedName());
+                MetricMemoizer<MethodLike> op = toplevel.getOperationMemoizer(node.getQualifiedName());
                 result.add((int) JavaMetricsComputer.INSTANCE.computeForOperation(opMetricKey, node, force,
                                                                                   MetricOptions.emptyOptions(), op));
                 return super.visit(node, data);
@@ -98,7 +99,7 @@ public class ProjectMemoizerTest {
 
 
         @Override
-        public double computeFor(ASTMethodOrConstructorDeclaration node, MetricOptions options) {
+        public double computeFor(MethodLike node, MetricOptions options) {
             return random.nextInt();
         }
     }
diff --git a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/impl/AbstractMetricTestRule.java b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/impl/AbstractMetricTestRule.java
index 083297d419..8d9ecb4090 100644
--- a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/impl/AbstractMetricTestRule.java
+++ b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/impl/AbstractMetricTestRule.java
@@ -11,7 +11,7 @@ import java.util.Map;
 
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTCompilationUnit;
-import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
+import net.sourceforge.pmd.lang.java.ast.MethodLike;
 import net.sourceforge.pmd.lang.java.metrics.JavaMetrics;
 import net.sourceforge.pmd.lang.java.metrics.api.JavaClassMetricKey;
 import net.sourceforge.pmd.lang.java.metrics.api.JavaOperationMetricKey;
@@ -157,7 +157,7 @@ public abstract class AbstractMetricTestRule extends AbstractJavaMetricsRule {
 
 
     @Override
-    public Object visit(ASTMethodOrConstructorDeclaration node, Object data) {
+    public Object visit(MethodLike node, Object data) {
         if (opKey != null && reportMethods && opKey.supports(node)) {
             double methodValue = JavaMetrics.get(opKey, node, metricOptions);
             if (methodValue >= reportLevel) {