1 /*
2  * Copyright 2019 Google LLC
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package com.google.auto.factory.processor;
17 
18 import static com.google.common.base.Preconditions.checkNotNull;
19 
20 import com.google.common.collect.ImmutableSet;
21 import java.util.HashSet;
22 import java.util.Set;
23 import javax.lang.model.element.Element;
24 import javax.lang.model.type.ArrayType;
25 import javax.lang.model.type.DeclaredType;
26 import javax.lang.model.type.IntersectionType;
27 import javax.lang.model.type.TypeMirror;
28 import javax.lang.model.type.TypeVariable;
29 import javax.lang.model.type.UnionType;
30 import javax.lang.model.type.WildcardType;
31 import javax.lang.model.util.SimpleTypeVisitor8;
32 
33 final class TypeVariables {
TypeVariables()34   private TypeVariables() {}
35 
getReferencedTypeVariables(TypeMirror type)36   static ImmutableSet<TypeVariable> getReferencedTypeVariables(TypeMirror type) {
37     checkNotNull(type);
38     return type.accept(ReferencedTypeVariables.INSTANCE, new HashSet<>());
39   }
40 
41   private static final class ReferencedTypeVariables extends
42       SimpleTypeVisitor8<ImmutableSet<TypeVariable>, Set<Element>> {
43 
44     private static final ReferencedTypeVariables INSTANCE = new ReferencedTypeVariables();
45 
ReferencedTypeVariables()46     ReferencedTypeVariables() {
47       super(ImmutableSet.of());
48     }
49 
50     @Override
visitArray(ArrayType t, Set<Element> visited)51     public ImmutableSet<TypeVariable> visitArray(ArrayType t, Set<Element> visited) {
52       return t.getComponentType().accept(this, visited);
53     }
54 
55     @Override
visitDeclared( DeclaredType t, Set<Element> visited)56     public ImmutableSet<TypeVariable> visitDeclared(
57         DeclaredType t, Set<Element> visited) {
58       if (!visited.add(t.asElement())) {
59         return ImmutableSet.of();
60       }
61       ImmutableSet.Builder<TypeVariable> typeVariables = ImmutableSet.builder();
62       for (TypeMirror typeArgument : t.getTypeArguments()) {
63         typeVariables.addAll(typeArgument.accept(this, visited));
64       }
65       return typeVariables.build();
66     }
67 
68     @Override
visitTypeVariable( TypeVariable t, Set<Element> visited)69     public ImmutableSet<TypeVariable> visitTypeVariable(
70         TypeVariable t, Set<Element> visited) {
71       if (!visited.add(t.asElement())) {
72         return ImmutableSet.of();
73       }
74       ImmutableSet.Builder<TypeVariable> typeVariables = ImmutableSet.builder();
75       typeVariables.add(t);
76       typeVariables.addAll(t.getLowerBound().accept(this, visited));
77       typeVariables.addAll(t.getUpperBound().accept(this, visited));
78       return typeVariables.build();
79     }
80 
81     @Override
visitUnion( UnionType t, Set<Element> visited)82     public ImmutableSet<TypeVariable> visitUnion(
83         UnionType t, Set<Element> visited) {
84       ImmutableSet.Builder<TypeVariable> typeVariables = ImmutableSet.builder();
85       for (TypeMirror unionType : t.getAlternatives()) {
86         typeVariables.addAll(unionType.accept(this, visited));
87       }
88       return typeVariables.build();
89     }
90 
91     @Override
visitIntersection( IntersectionType t, Set<Element> visited)92     public ImmutableSet<TypeVariable> visitIntersection(
93         IntersectionType t, Set<Element> visited) {
94       ImmutableSet.Builder<TypeVariable> typeVariables = ImmutableSet.builder();
95       for (TypeMirror intersectionType : t.getBounds()) {
96         typeVariables.addAll(intersectionType.accept(this, visited));
97       }
98       return typeVariables.build();
99     }
100 
101     @Override
visitWildcard( WildcardType t, Set<Element> visited)102     public ImmutableSet<TypeVariable> visitWildcard(
103         WildcardType t, Set<Element> visited) {
104       ImmutableSet.Builder<TypeVariable> typeVariables = ImmutableSet.builder();
105       TypeMirror extendsBound = t.getExtendsBound();
106       if (extendsBound != null) {
107         typeVariables.addAll(extendsBound.accept(this, visited));
108       }
109       TypeMirror superBound = t.getSuperBound();
110       if (superBound != null) {
111         typeVariables.addAll(superBound.accept(this, visited));
112       }
113       return typeVariables.build();
114     }
115   }
116 }
117