Fix OnlyCatchDeclaredExceptions to skip generic type variables

When a method throws a generic type parameter (e.g., `<TE extends Throwable>`),
the recipe should not attempt to replace the generic catch block. Generic type
variables cannot be used in multi-catch blocks and attempting to do so causes
an IllegalArgumentException during JavaTemplate parsing.

This fix adds a check to skip transformation when any of the thrown exceptions
is a generic type variable, ensuring the recipe only operates on concrete
exception types.

Fixes #715

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: timtebeek

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

@@ -64,7 +64,7 @@ public J.Try visitTry(J.Try aTry, ExecutionContext ctx) {
                         // Find declared thrown exceptions that are not already specifically caught
                         Set<JavaType> declaredThrown = getDeclaredThrownExceptions(t);
                         declaredThrown.removeAll(getCaughtExceptions(t));
-                        if (!declaredThrown.isEmpty()) {
+                        if (!declaredThrown.isEmpty() && !containsGenericTypeVariable(declaredThrown)) {
                             return multiCatchWithDeclaredExceptions(c, declaredThrown);
                         }
                     }
@@ -81,6 +81,15 @@ private boolean isGenericCatch(J.Try.Catch aCatch) {
                 return false;
             }
 
+            private boolean containsGenericTypeVariable(Set<JavaType> types) {
+                for (JavaType type : types) {
+                    if (type instanceof JavaType.GenericTypeVariable) {
+                        return true;
+                    }
+                }
+                return false;
+            }
+
             private Set<JavaType> getCaughtExceptions(J.Try aTry) {
                 Set<JavaType> caughtExceptions = new HashSet<>();
                 for (J.Try.Catch c : aTry.getCatches()) {

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

@@ -453,4 +453,30 @@ void doSomething() {
           )
         );
     }
+
+    @Test
+    @org.openrewrite.Issue("https://github.com/openrewrite/rewrite-static-analysis/issues/715")
+    void doNotChangeWhenThrownExceptionIsGeneric() {
+        rewriteRun(
+          spec -> spec.parser(JavaParser.fromJavaVersion()),
+          //language=java
+          java(
+            """
+              interface ThrowsGenerics<TE extends Throwable> {
+                  void get() throws TE;
+              }
+              
+              class MyService {
+                  void doSomething(ThrowsGenerics<Exception> t) {
+                      try {
+                          t.get();
+                      } catch (Exception e) {
+                          // Should not be changed - thrown exception is generic
+                      }
+                  }
+              }
+              """
+          )
+        );
+    }
 }