infer more contracts for if statements without else (IDEA-132872)

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/ContractInference.java

@@ -34,7 +34,6 @@ import com.siyeh.ig.psiutils.SideEffectChecker;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
@@ -178,7 +177,7 @@ class ContractInferenceInterpreter {
       }
     });
     if (notNull) {
-      return ContainerUtil.concat(fromDelegate, Arrays.asList(new MethodContract(myEmptyConstraints, NOT_NULL_VALUE)));
+      return ContainerUtil.concat(fromDelegate, Collections.singletonList(new MethodContract(myEmptyConstraints, NOT_NULL_VALUE)));
     }
     return fromDelegate;
   }
@@ -365,7 +364,7 @@ class ContractInferenceInterpreter {
         PsiStatement elseBranch = ((PsiIfStatement)statement).getElseBranch();
         if (elseBranch != null) {
           result.addAll(visitStatements(falseStates, elseBranch));
-        } else if (alwaysReturns(thenBranch)) {
+        } else {
           states = falseStates;
           continue;
         }
@@ -404,22 +403,6 @@ class ContractInferenceInterpreter {
     return false;
   }
 
-  private static boolean alwaysReturns(@Nullable PsiStatement statement) {
-    if (statement instanceof PsiReturnStatement || statement instanceof PsiThrowStatement) return true;
-    if (statement instanceof PsiBlockStatement) {
-      for (PsiStatement child : ((PsiBlockStatement)statement).getCodeBlock().getStatements()) {
-        if (alwaysReturns(child)) {
-          return true;
-        }
-      }
-    }
-    if (statement instanceof PsiIfStatement) {
-      return alwaysReturns(((PsiIfStatement)statement).getThenBranch()) &&
-             alwaysReturns(((PsiIfStatement)statement).getElseBranch());
-    }
-    return false;
-  }
-
   @Nullable
   private static ValueConstraint getLiteralConstraint(@Nullable PsiExpression expr) {
     if (expr instanceof PsiLiteralExpression) {

java/java-tests/testSrc/com/intellij/codeInspection/ContractInferenceFromSourceTest.groovy

@@ -148,7 +148,7 @@ class ContractInferenceFromSourceTest extends LightCodeInsightFixtureTestCase {
     return true;
   }
 """)
-    assert c == []
+    assert c == ['null -> true']
   }
 
   void "test assertion"() {
@@ -391,6 +391,23 @@ class ContractInferenceFromSourceTest extends LightCodeInsightFixtureTestCase {
     assert c == ['null -> null']
   }
 
+  public void "test return after if without else"() {
+    def c = inferContracts("""
+public static boolean isBlank(String s) {
+        if (s != null) {
+            final int l = s.length();
+            for (int i = 0; i < l; i++) {
+                final char c = s.charAt(i);
+                if (c != ' ') {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }    """)
+    assert c == ['null -> true']
+  }
+
   private String inferContract(String method) {
     return assertOneElement(inferContracts(method))
   }