Fix RemoveUnusedLocalVariables to preserve assignments with side effects

src/main/java/org/openrewrite/staticanalysis/RemoveUnusedLocalVariables.java

@@ -171,7 +171,7 @@ public J.DeconstructionPattern visitDeconstructionPattern(J.DeconstructionPatter
                     // skip if defined as a parameter to a lambda expression
                     parent instanceof J.Lambda ||
                     // skip if the initializer may have a side effect
-                    initializerMightSideEffect(variable)
+                    mightSideEffect(variable.getInitializer())
                 ) {
                     return variable;
                 }
@@ -181,6 +181,9 @@ public J.DeconstructionPattern visitDeconstructionPattern(J.DeconstructionPatter
                     List<Statement> assignmentReferences = VariableReferences.findLhsReferences(parentScope.getValue(), variable.getName());
                     for (Statement ref : assignmentReferences) {
                         if (ref instanceof J.Assignment) {
+                            if (mightSideEffect(((J.Assignment) ref).getAssignment())) {
+                                return variable;
+                            }
                             doAfterVisit(new PruneAssignmentExpression((J.Assignment) ref));
                         }
                         doAfterVisit(new DeleteStatement<>(ref));
@@ -216,18 +219,14 @@ public J.VariableDeclarations visitVariableDeclarations(J.VariableDeclarations m
                 return mv;
             }
 
-            private boolean initializerMightSideEffect(J.VariableDeclarations.NamedVariable variable) {
-                if (variable.getInitializer() == null) {
-                    return false;
-                }
-                AtomicBoolean mightSideEffect = new AtomicBoolean(false);
-                new JavaIsoVisitor<AtomicBoolean>() {
+            private boolean mightSideEffect(Expression initializer) {
+                return initializer != null && new JavaIsoVisitor<AtomicBoolean>() {
                     @Override
                     public J.MethodInvocation visitMethodInvocation(J.MethodInvocation methodInvocation, AtomicBoolean result) {
                         if (SAFE_GETTER_METHODS.matches(methodInvocation)) {
                             return methodInvocation;
                         }
-                        if (withSideEffects == null || Boolean.FALSE.equals(withSideEffects)) {
+                        if (withSideEffects == null || !withSideEffects) {
                             result.set(true);
                         }
                         return methodInvocation;
@@ -244,8 +243,7 @@ public J.Assignment visitAssignment(J.Assignment assignment, AtomicBoolean resul
                         result.set(true);
                         return assignment;
                     }
-                }.visit(variable.getInitializer(), mightSideEffect);
-                return mightSideEffect.get();
+                }.reduce(initializer, new AtomicBoolean(false)).get();
             }
         });
     }

src/test/java/org/openrewrite/staticanalysis/RemoveUnusedLocalVariablesTest.java

@@ -704,7 +704,7 @@ static void method() {
                       try {
                           used = new Object();
                           assertEquals(used, null);
-                          unused = new Object();
+                          unused = used;
                       } catch (Exception e) {
                           // do nothing
                       }
@@ -1192,6 +1192,29 @@ void method() {
         );
     }
 
+    @Issue("https://github.com/openrewrite/rewrite-static-analysis/issues/740")
+    @Test
+    void doNotRemoveVariableAssignmentWithPotentialSideEffects() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              class Test {
+                  private String baz() {
+                      String foo;
+                      try {
+                          foo = String.valueOf(1);
+                      } catch (RuntimeException e) {
+                          return "error";
+                      }
+                      return "ok";
+                  }
+              }
+              """
+          )
+        );
+    }
+
     @Issue("https://github.com/openrewrite/rewrite-static-analysis/issues/760")
     @Test
     void doNotRemoveUnusedPatternMatchingVariables() {