feature: CtTypeParamer#getTypeErasure, getTypeAdaptedTo

src/main/java/spoon/reflect/declaration/CtTypeParameter.java

@@ -40,6 +40,20 @@ public interface CtTypeParameter extends CtType<Object> {
 	@DerivedProperty
 	CtFormalTypeDeclarer getTypeParameterDeclarer();
 
+	/**
+	 * @return type (not generic one), which is used by java compiler to ensure that no new classes are created for parameterized types;
+	 * consequently, generics incur no runtime overhead.
+	 * See https://docs.oracle.com/javase/tutorial/java/generics/erasure.html
+	 */
+	@DerivedProperty
+	CtTypeReference<?> getTypeErasure();
+
+	/**
+	 * @param targetScope - the scope where this type parameter is needed
+	 * @return type reference adapted from origin scope to scope of `targetScope`
+	 */
+	CtTypeReference<?> getTypeAdaptedTo(CtFormalTypeDeclarer targetScope);
+
 	// override the return type
 	@Override
 	CtTypeParameter clone();

src/main/java/spoon/support/reflect/declaration/CtTypeParameterImpl.java

@@ -16,12 +16,15 @@
  */
 package spoon.support.reflect.declaration;
 
+import spoon.SpoonException;
+import spoon.reflect.declaration.CtConstructor;
 import spoon.reflect.declaration.CtField;
 import spoon.reflect.declaration.CtFormalTypeDeclarer;
 import spoon.reflect.declaration.CtMethod;
 import spoon.reflect.declaration.CtModifiable;
 import spoon.reflect.declaration.CtPackage;
 import spoon.reflect.declaration.CtType;
+import spoon.reflect.declaration.CtTypeMember;
 import spoon.reflect.declaration.CtTypeParameter;
 import spoon.reflect.declaration.ModifierKind;
 import spoon.reflect.declaration.ParentNotInitializedException;
@@ -248,6 +251,148 @@ public boolean isSubtypeOf(CtTypeReference<?> type) {
 		return getReference().isSubtypeOf(type);
 	}
 
+	@Override
+	public CtTypeReference<?> getTypeErasure() {
+		CtTypeReference<?> boundType = getBound(this);
+		CtTypeReference<?> typeErasure = getReferenceInScope(boundType, getDeclaringType());
+		if (typeErasure instanceof CtTypeParameterReference) {
+			CtTypeParameterReference typeRef = (CtTypeParameterReference) typeErasure;
+			return typeRef.getDeclaration().getTypeErasure();
+		}
+		return typeErasure;
+	}
+
+	@Override
+	public CtTypeReference<?> getTypeAdaptedTo(CtFormalTypeDeclarer targetScope) {
+		CtFormalTypeDeclarer scope = getTypeParameterDeclarer();
+		if (scope == null) {
+			throw new SpoonException("Can't adapt type param to another scope if it has no current scope (no parent formal type declarer).");
+		}
+		if (targetScope == scope) {
+			//type parameter is declared in required scope. Just return it.
+			return getReference();
+		}
+		if (scope instanceof CtType) {
+			if ((targetScope instanceof CtType) == false && targetScope instanceof CtTypeMember) {
+				targetScope = ((CtTypeMember) targetScope).getDeclaringType();
+				if (targetScope == scope) {
+					//type parameter is declared in required scope. Just return it.
+					return getReference();
+				}
+			}
+			if (targetScope instanceof CtType) {
+				return getReferenceInTypeScope(this, (CtType<?>) targetScope, (CtType<?>) scope);
+			}
+			//cannot map from Type scope to another scope
+			return null;
+		} else if (scope instanceof CtMethod) {
+			if (targetScope instanceof CtMethod) {
+				if (scope.getFormalCtTypeParameters().size() != targetScope.getFormalCtTypeParameters().size()) {
+					//cannot map type parameter of method 1 to method 2 if they have different number of formal type parameters
+					return null;
+				}
+				int myPosition = getTypeParameterPosition(this, scope);
+				return targetScope.getFormalCtTypeParameters().get(myPosition).getReference();
+			}
+			return null;
+		} else if (scope instanceof CtConstructor) {
+			//cannot map to scope of different constructor
+			return null;
+		} else {
+			throw new SpoonException("Unexpected scope of type parameter of type: " + scope.getClass().getName());
+		}
+	}
+
+	/**
+	 * Converts potentially generic parameters from namespace of some super class to namespace of `targetScope`
+	 * @param type - the reference to to be converted parameter (generic) type or normal type.
+	 * @param targetScope - the type which represents target scope of the generic parameter.
+	 * @return a `type` converted into scope of `targetType` or null if conversion is not possible, because scopes are incompatible
+	 */
+	private static CtTypeReference<?> getReferenceInScope(CtTypeReference<?> type, CtType<?> targetScope) {
+		if (type instanceof CtTypeParameterReference) {
+			CtTypeParameterReference typeParamRef = (CtTypeParameterReference) type;
+			CtTypeParameter typeParam = typeParamRef.getDeclaration();
+			CtFormalTypeDeclarer scope = typeParam.getTypeParameterDeclarer();
+			if (scope == null) {
+				throw new SpoonException("Can't convert scope of type param if it has no parent formal type declarer.");
+			}
+			if (targetScope == scope) {
+				//type parameter is declared in required scope. Just return it.
+				return typeParamRef;
+			}
+			if (scope instanceof CtType) {
+				//this type reference is declared in scope of different type. Compute how it is declared in `targetType`
+				return getReferenceInTypeScope(typeParam, targetScope, (CtType<?>) scope);
+			} else if (scope instanceof CtMethod) {
+
+			} else if (scope instanceof CtConstructor) {
+
+			} else {
+				throw new SpoonException("Unexpected scope of type parameter of type: " + scope.getClass().getName());
+			}
+		}
+		return type;
+	}
+
+
+	/**
+	 * Converts generic `typeParam` in scope of type `sourceScope` to namespace of `targetScope`
+	 * @param typeParam the to be converted type parameter
+	 * @param targetScope - type of target scope, which should be a sub type of source scope
+	 * @param sourceScope - type of source scope
+	 * @return reference to type converted into targetScope
+	 */
+	private static CtTypeReference<?> getReferenceInTypeScope(CtTypeParameter typeParam, CtType<?> targetScope, CtType<?> sourceScope) {
+		if (targetScope == sourceScope) {
+			return typeParam.getReference();
+		}
+		CtTypeReference<?> superTypeRef = targetScope.getSuperclass();
+		if (superTypeRef == null) {
+			return null;
+		}
+		CtType<?> superType = superTypeRef.getTypeDeclaration();
+		if (superType == null) {
+			return null;
+		}
+		CtTypeReference<?> superTypeParamRef = getReferenceInTypeScope(typeParam, superType, sourceScope);
+		if (superTypeParamRef instanceof CtTypeParameterReference) {
+			CtTypeParameter superTypeParam = ((CtTypeParameterReference) superTypeParamRef).getDeclaration();
+			//convert typeParam  of super type to typeParam of `targetType`
+			int paramTypeIdxInSuperType = getTypeParameterPosition(superTypeParam, superType);
+			List<CtTypeReference<?>> actTRs = superTypeRef.getActualTypeArguments();
+			if (paramTypeIdxInSuperType < actTRs.size()) {
+				//the actual type argument is defined in `targetType`. Return that type parameter declared in targetScope
+				return actTRs.get(paramTypeIdxInSuperType);
+			}
+			//the super type actual type arguments are not defined in sub class. The type erasure is applied
+			return superTypeParam.getTypeErasure();
+		}
+		//else it is normal type reference.
+		return superTypeParamRef;
+	}
+
+	private static CtTypeReference<?> getBound(CtTypeParameter typeParam) {
+		CtTypeReference<?> bound = typeParam.getSuperclass();
+		if (bound == null) {
+			bound = typeParam.getFactory().Type().OBJECT;
+		}
+		return bound;
+	}
+
+	/**
+	 * @param parameterType
+	 * @param scope
+	 * @return index of parameterType declaration in scope or throws SpoonException if not found (= spoon model inconsistency)
+	 */
+	private static int getTypeParameterPosition(CtTypeParameter parameterType, CtFormalTypeDeclarer scope) {
+		int position = scope.getFormalCtTypeParameters().indexOf(parameterType);
+		if (position == -1) {
+			throw new SpoonException("Type parameter <" + parameterType.getSimpleName() + " not found in scope " + scope.getShortRepresentation());
+		}
+		return position;
+	}
+
 	@Override
 	@UnsettableProperty
 	public <M, C extends CtType<Object>> C addMethod(CtMethod<M> method) {

src/test/java/spoon/test/ctType/CtTypeParameterTest.java

@@ -0,0 +1,111 @@
+package spoon.test.ctType;
+
+import java.lang.reflect.Executable;
+import java.lang.reflect.Field;
+import java.util.List;
+
+import org.junit.Test;
+
+import spoon.reflect.declaration.CtClass;
+import spoon.reflect.declaration.CtConstructor;
+import spoon.reflect.declaration.CtExecutable;
+import spoon.reflect.declaration.CtFormalTypeDeclarer;
+import spoon.reflect.declaration.CtMethod;
+import spoon.reflect.declaration.CtParameter;
+import spoon.reflect.declaration.CtType;
+import spoon.reflect.declaration.CtTypeMember;
+import spoon.reflect.declaration.CtTypeParameter;
+import spoon.reflect.visitor.filter.NameFilter;
+import spoon.test.ctType.testclasses.ErasureModelA;
+import spoon.testing.utils.ModelUtils;
+
+import static org.junit.Assert.*;
+
+public class CtTypeParameterTest {
+
+	@Test
+	public void testTypeErasure() throws Exception {
+		CtClass<?> ctModel = (CtClass<?>) ModelUtils.buildClass(ErasureModelA.class);
+		checkType(ctModel);
+	}
+
+	private void checkType(CtType<?> type) throws NoSuchFieldException, SecurityException {
+		List<CtTypeParameter> l_typeParams = type.getFormalCtTypeParameters();
+		for (CtTypeParameter ctTypeParameter : l_typeParams) {
+			checkTypeParamErasureOfType(ctTypeParameter, type.getActualClass());
+		}
+
+		for (CtTypeMember typeMemeber : type.getTypeMembers()) {
+			if (typeMemeber instanceof CtFormalTypeDeclarer) {
+				CtFormalTypeDeclarer ftDecl = (CtFormalTypeDeclarer) typeMemeber;
+				l_typeParams = ftDecl.getFormalCtTypeParameters();
+				if (typeMemeber instanceof CtExecutable<?>) {
+					CtExecutable<?> exec = (CtExecutable<?>) typeMemeber;
+					for (CtTypeParameter ctTypeParameter : l_typeParams) {
+						checkTypeParamErasureOfExecutable(ctTypeParameter, exec);
+					}
+				} else if (typeMemeber instanceof CtType<?>) {
+					CtType<?> nestedType = (CtType<?>) typeMemeber;
+					checkType(nestedType);
+				}
+			}
+		}
+	}
+
+	private void checkTypeParamErasureOfType(CtTypeParameter typeParam, Class<?> clazz) throws NoSuchFieldException, SecurityException {
+		Field field = clazz.getDeclaredField("param"+typeParam.getSimpleName());
+		assertEquals("TypeErasure of type param "+getTypeParamIdentification(typeParam), field.getType().getName(), typeParam.getTypeErasure().getQualifiedName());
+	}
+
+	private void checkTypeParamErasureOfExecutable(CtTypeParameter typeParam, CtExecutable<?> exec) throws NoSuchFieldException, SecurityException {
+		CtParameter<?> param = exec.filterChildren(new NameFilter<>("param"+typeParam.getSimpleName())).first();
+		assertNotNull("Missing param"+typeParam.getSimpleName() + " in "+ exec.getSignature(), param);
+		int paramIdx = exec.getParameters().indexOf(param);
+		Class declClass = exec.getParent(CtType.class).getActualClass();
+		Executable declExec;
+		if (exec instanceof CtConstructor) {
+			declExec = declClass.getDeclaredConstructors()[0];
+		} else {
+			declExec = declClass.getDeclaredMethods()[0];
+		}
+		Class<?> paramType = declExec.getParameterTypes()[paramIdx];
+		assertEquals("TypeErasure of executable param "+getTypeParamIdentification(typeParam), paramType.getName(), typeParam.getTypeErasure().getQualifiedName());
+	}
+
+	private String getTypeParamIdentification(CtTypeParameter typeParam) {
+		String result = "<"+typeParam.getSimpleName()+">";
+		CtFormalTypeDeclarer l_decl = typeParam.getParent(CtFormalTypeDeclarer.class);
+		if (l_decl instanceof CtType) {
+			return ((CtType) l_decl).getQualifiedName()+result;
+		}
+		if (l_decl instanceof CtExecutable) {
+			CtExecutable exec = (CtExecutable) l_decl;
+			if (exec instanceof CtMethod) {
+				result=exec.getSignature()+result;
+			}
+			return exec.getParent(CtType.class).getQualifiedName()+"#"+result;
+		}
+		throw new AssertionError();
+	}
+
+	@Test
+	public void testTypeAdapted() throws Exception {
+		CtClass<?> ctModel = (CtClass<?>) ModelUtils.buildClass(ErasureModelA.class);
+		CtTypeParameter tpA = ctModel.getFormalCtTypeParameters().get(0);
+		CtTypeParameter tpB = ctModel.getFormalCtTypeParameters().get(1);
+		CtTypeParameter tpC = ctModel.getFormalCtTypeParameters().get(2);
+		CtTypeParameter tpD = ctModel.getFormalCtTypeParameters().get(3);
+
+		CtClass<?> ctModelB = ctModel.filterChildren(new NameFilter<>("ModelB")).first();
+		assertEquals("A2", tpA.getTypeAdaptedTo(ctModelB).getQualifiedName());
+		assertEquals("B2", tpB.getTypeAdaptedTo(ctModelB).getQualifiedName());
+		assertEquals("C2", tpC.getTypeAdaptedTo(ctModelB).getQualifiedName());
+		assertEquals("D2", tpD.getTypeAdaptedTo(ctModelB).getQualifiedName());
+
+		CtClass<?> ctModelC = ctModel.filterChildren(new NameFilter<>("ModelC")).first();
+		assertEquals("java.lang.Integer", tpA.getTypeAdaptedTo(ctModelC).getQualifiedName());
+		assertEquals("java.lang.RuntimeException", tpB.getTypeAdaptedTo(ctModelC).getQualifiedName());
+		assertEquals("java.lang.IllegalArgumentException", tpC.getTypeAdaptedTo(ctModelC).getQualifiedName());
+		assertEquals("spoon.test.ctType.testclasses.ErasureModelA$ModelC", tpD.getTypeAdaptedTo(ctModelC).getQualifiedName());
+	}
+}

src/test/java/spoon/test/ctType/testclasses/ErasureModelA.java

@@ -0,0 +1,40 @@
+package spoon.test.ctType.testclasses;
+
+public class ErasureModelA<A, B extends Exception, C extends B, D extends ErasureModelA<A,B,C,D>> {
+
+	A paramA;
+	B paramB;
+	C paramC;
+	D paramD;
+
+	public <I, J extends C> ErasureModelA(I paramI, J paramJ, D paramD) {
+	}
+
+	public <I, J extends C> void method(I paramI, J paramJ, D paramD) {
+	}
+
+	static class ModelB<A2,B2 extends Exception, C2 extends B2, D2 extends ErasureModelA<A2,B2,C2,D2>> extends ErasureModelA<A2,B2,C2,D2> {
+		A2 paramA2;
+		B2 paramB2;
+		C2 paramC2;
+		D2 paramD2;
+
+		public <I, J extends C2> ModelB(I paramI, J paramJ, D2 paramD2) {
+			super(paramI, paramJ, paramD2);
+		}
+
+		@Override
+		public <I, J extends C2> void method(I paramI, J paramJ, D2 paramD2) {
+		}
+	}
+
+	static class ModelC extends ErasureModelA<Integer, RuntimeException, IllegalArgumentException, ModelC> {
+
+		public ModelC(Float paramI, IllegalArgumentException paramJ, ModelC paramK) {
+			super(paramI, paramJ, null);
+		}
+
+		public void method(Float paramI, IllegalArgumentException paramJ, ModelC paramK) {
+		}
+	}
+}