Fix CatchCauseOnlyRethrows onlyRethrows check for multi catch statements (#355)

* Fix CatchCauseOnlyRethrows rethrows check for multi catch statements

* Specifically check for `JavaType.MultiCatch`

---------

Co-authored-by: Niels de Bruin <niels.de.bruin@jdriven.com>
Co-authored-by: Tim te Beek <tim@moderne.io>

Author: 3 people

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

@@ -20,7 +20,10 @@
 import org.openrewrite.TreeVisitor;
 import org.openrewrite.internal.ListUtils;
 import org.openrewrite.java.JavaIsoVisitor;
-import org.openrewrite.java.tree.*;
+import org.openrewrite.java.tree.Expression;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaType;
+import org.openrewrite.java.tree.TypeUtils;
 
 import java.time.Duration;
 import java.util.Set;
@@ -37,7 +40,7 @@ public String getDisplayName() {
     @Override
     public String getDescription() {
         return "A `catch` clause that only rethrows the caught exception is unnecessary. " +
-                "Letting the exception bubble up as normal achieves the same result with less code.";
+               "Letting the exception bubble up as normal achieves the same result with less code.";
     }
 
     @Override
@@ -105,16 +108,18 @@ private boolean hasWiderExceptionType(J.Try.Catch aCatch, J.Try.Catch next) {
 
             private boolean onlyRethrows(J.Try.Catch aCatch) {
                 if (aCatch.getBody().getStatements().size() != 1 ||
-                        !(aCatch.getBody().getStatements().get(0) instanceof J.Throw)) {
+                    !(aCatch.getBody().getStatements().get(0) instanceof J.Throw)) {
                     return false;
                 }
 
                 Expression exception = ((J.Throw) aCatch.getBody().getStatements().get(0)).getException();
-                JavaType.FullyQualified catchType = TypeUtils.asFullyQualified(aCatch.getParameter().getType());
-                if (catchType == null || !catchType.equals(exception.getType())) {
-                    return false;
+                JavaType catchParameterType = aCatch.getParameter().getType();
+                if (!(catchParameterType instanceof JavaType.MultiCatch)) {
+                    JavaType.FullyQualified catchType = TypeUtils.asFullyQualified(catchParameterType);
+                    if (catchType == null || !catchType.equals(exception.getType())) {
+                        return false;
+                    }
                 }
-
                 if (exception instanceof J.Identifier) {
                     return ((J.Identifier) exception).getSimpleName().equals(aCatch.getParameter().getTree().getVariables().get(0).getSimpleName());
                 }

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

@@ -141,6 +141,71 @@ void foo() throws IOException {
         );
     }
 
+    @Test
+    void tryCanBeRemovedWithMultiCatch() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              import java.io.FileReader;
+              import java.io.IOException;
+              import java.io.FileNotFoundException;
+              
+              class A {
+                  void foo() throws IOException {
+                      try {
+                          new FileReader("").read();
+                      } catch (FileNotFoundException e) {
+                          throw e;
+                      } catch(IOException | ArrayIndexOutOfBoundsException e) {
+                          throw e;
+                      } catch(Exception e) {
+                          throw e;
+                      }
+                  }
+              }
+              """,
+            """
+            import java.io.FileReader;
+            import java.io.IOException;
+            import java.io.FileNotFoundException;
+              
+            class A {
+                void foo() throws IOException {
+                    new FileReader("").read();
+                }
+            }
+            """
+          )
+        );
+    }
+
+    @Test
+    void multiCatchPreservedOnDifferentThrow() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              import java.io.FileReader;
+              import java.io.IOException;
+              import java.io.FileNotFoundException;
+              
+              class A {
+                  void foo() throws IOException {
+                      try {
+                          new FileReader("").read();
+                      } catch (FileNotFoundException e) {
+                          throw e;
+                      } catch(IOException | ArrayIndexOutOfBoundsException e) {
+                          throw new IOException("another message", e);
+                      }
+                  }
+              }
+              """
+          )
+        );
+    }
+
     @Test
     void tryShouldBePreservedBecauseFinally() {
         rewriteRun(