DataFlowInspection: highlight method references known to return constant true/false value with quick-fix changing them to trivial lambdas (partially fixes IDEA-170885).

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/replaceWithTrivialLambda/afterMethodRef.java

@@ -0,0 +1,29 @@
+// "Fix all 'Constant conditions & exceptions' problems in file" "true"
+import org.jetbrains.annotations.*;
+
+import java.util.*;
+import java.util.stream.Stream;
+
+public class MethodReferenceConstantValue {
+  @Contract(value = "!null -> false", pure = true)
+  public boolean strangeMethod(String s) {
+    return s == null ? new Random().nextBoolean() : false;
+  }
+
+  public void test(Optional<String> opt) {
+    X x = (methodReferenceConstantValue, s) -> false;
+    Boolean aBoolean = opt.map(s -> false)
+      .map(o -> true)
+      .map(o -> false)
+      .orElse(false);
+    if (opt.isPresent()) {
+      Stream.generate(() -> true)
+        .limit(10)
+        .forEach(System.out::println);
+    }
+  }
+
+  interface X {
+    boolean action(@Nullable MethodReferenceConstantValue a, @NotNull String b);
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/replaceWithTrivialLambda/beforeMethodRef.java

@@ -0,0 +1,29 @@
+// "Fix all 'Constant conditions & exceptions' problems in file" "true"
+import org.jetbrains.annotations.*;
+
+import java.util.*;
+import java.util.stream.Stream;
+
+public class MethodReferenceConstantValue {
+  @Contract(value = "!null -> false", pure = true)
+  public boolean strangeMethod(String s) {
+    return s == null ? new Random().nextBoolean() : false;
+  }
+
+  public void test(Optional<String> opt) {
+    X x = MethodReferenceConstantValue::strangeMethod;
+    Boolean aBoolean = opt.map(th<caret>is::strangeMethod)
+      .map(Objects::nonNull)
+      .map(Objects::isNull)
+      .orElse(false);
+    if (opt.isPresent()) {
+      Stream.generate(opt::isPresent)
+        .limit(10)
+        .forEach(System.out::println);
+    }
+  }
+
+  interface X {
+    boolean action(@Nullable MethodReferenceConstantValue a, @NotNull String b);
+  }
+}