Fix generics handling error

Under the hood, the root cause seemed to be this:

Caused by: java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractMap.put(AbstractMap.java:209)
	at org.codehaus.groovy.control.ResolveVisitor.resolveGenericsHeader(ResolveVisitor.java:1452)
	at org.codehaus.groovy.control.ResolveVisitor.resolveGenericsHeader(ResolveVisitor.java:1409)

Based on a look in the debugger, without this change, the
genericParameterNames field will be a Collections$EmptyMap, which is
immutable and therefore doesn't support PUT operations.

Author: jonnybot0

src/main/java/org/codehaus/groovy/control/ResolveVisitor.java

@@ -1279,7 +1279,7 @@ public void visitClass(final ClassNode node) {
             if (!Modifier.isStatic(node.getModifiers()))
                 genericParameterNames.putAll(outerNames); // outer names visible
         } else {
-            genericParameterNames.clear(); // outer class: new generic namespace
+            genericParameterNames = new HashMap<>(); // outer class: new generic namespace
         }
         resolveGenericsHeader(node.getGenericsTypes());
         switch (phase) { // GROOVY-9866, GROOVY-10466

src/test/groovy/groovy/util/GroovyScriptEngineReloadingTest.groovy

@@ -182,6 +182,39 @@ final class GroovyScriptEngineReloadingTest {
 
     }
 
+    @Test
+    void testRecompilingWithGenericsAndConstants() {
+        MapFileSystem.instance.modFile('BaseClass.groovy', 'class BaseClass<T> {}', gse.@time)
+
+        def tertiaryClassText = '''
+            class NotGeneric {
+                /**
+                 * Not typed on purpose - if typed as String then NotGeneric is no longer a dependency of
+                 * ParameterisedClass for some reason...
+                 */
+                public static final Object CONSTANT = "not generic"
+            }
+        '''
+        MapFileSystem.instance.modFile('NotGeneric.groovy', tertiaryClassText, gse.@time)
+
+        def subClassText = '''
+            class SubClass extends BaseClass<String> {
+                public static final String CONSTANT = NotGeneric.CONSTANT
+            }
+        '''
+        MapFileSystem.instance.modFile('SubClass.groovy', subClassText, gse.@time)
+
+        MapFileSystem.instance.modFile('scriptUsingGeneric.groovy', 'SubClass.CONSTANT', gse.@time)
+
+
+        gse.loadScriptByName('scriptUsingGeneric.groovy')
+        sleep 1000
+
+        // make a change to the sub-class so that it gets recompiled
+        MapFileSystem.instance.modFile('SubClass.groovy', subClassText + '\n', gse.@time)
+        gse.loadScriptByName('scriptUsingGeneric.groovy')
+    }
+
     @Test
     void testDeleteDependent() {
         sleep 10000