Fix UnnecessaryThrows to check actual close() method exceptions (#812)

The recipe was incorrectly removing throws declarations from methods
using try-with-resources because it made blanket assumptions that all
Closeable types throw IOException and all AutoCloseable types throw
Exception.

Instead, the fix looks up the actual close() method on the resource
type and checks what exceptions it declares, using the same mechanism
already used for method invocations.

Fixes #728

Co-authored-by: Tim te Beek <tim@mac.home>

Author: timtebeek

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

@@ -79,10 +79,12 @@ public J.Try.Resource visitTryResource(J.Try.Resource tryResource, ExecutionCont
 
                             JavaType.FullyQualified resourceType = TypeUtils.asFullyQualified(resource.getType());
                             if (resourceType != null) {
-                                if (TypeUtils.isAssignableTo(JavaType.ShallowClass.build("java.io.Closeable"), resourceType)) {
-                                    unusedThrows.remove(JavaType.ShallowClass.build("java.io.IOException"));
-                                } else if (TypeUtils.isAssignableTo(JavaType.ShallowClass.build("java.lang.AutoCloseable"), resourceType)) {
-                                    unusedThrows.remove(JavaType.ShallowClass.build("java.lang.Exception"));
+                                // Find the close() method on the resource type to get its actual thrown exceptions
+                                for (JavaType.Method method : resourceType.getMethods()) {
+                                    if ("close".equals(method.getName()) && method.getParameterTypes().isEmpty()) {
+                                        removeThrownTypes(method);
+                                        break;
+                                    }
                                 }
                             }
 

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

@@ -85,6 +85,27 @@ public <E extends Exception> void accept(Class<E> e) throws E {
         );
     }
 
+    @Issue("https://github.com/openrewrite/rewrite-static-analysis/issues/728")
+    @SuppressWarnings("EmptyTryBlock")
+    @Test
+    void necessaryThrowsFromInputStreamClose() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              import java.io.InputStream;
+
+              class Test {
+                  void customStripSpaceXSL() throws Exception {
+                      try (InputStream is = getClass().getClassLoader().getResourceAsStream("foo.xsl")) {
+                      }
+                  }
+              }
+              """
+          )
+        );
+    }
+
     @Issue("https://github.com/openrewrite/rewrite/issues/631")
     @SuppressWarnings("EmptyTryBlock")
     @Test