test/langtools/tools/lib/types/TypeHarness.java - platform/libcore - Git at Google

 /*
  * Copyright (c) 2010, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */

 import java.net.URI;
 import java.util.ArrayList;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;

 import javax.tools.JavaFileObject;
 import javax.tools.SimpleJavaFileObject;

 import com.sun.tools.javac.code.BoundKind;
 import com.sun.tools.javac.code.Flags;
 import com.sun.tools.javac.util.Context;
 import com.sun.tools.javac.code.Types;
 import com.sun.tools.javac.code.Symtab;
 import com.sun.tools.javac.code.Type;
 import com.sun.tools.javac.code.Type.*;
 import com.sun.tools.javac.code.Symbol.*;
 import com.sun.tools.javac.comp.Attr;
 import com.sun.tools.javac.comp.Check;
 import com.sun.tools.javac.comp.Infer;
 import com.sun.tools.javac.comp.InferenceContext;
 import com.sun.tools.javac.comp.Modules;
 import com.sun.tools.javac.util.List;
 import com.sun.tools.javac.util.ListBuffer;
 import com.sun.tools.javac.util.Name;
 import com.sun.tools.javac.util.Names;
 import com.sun.tools.javac.file.JavacFileManager;
 import com.sun.tools.javac.main.JavaCompiler;
 import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
 import com.sun.tools.javac.util.Abort;
 import com.sun.tools.javac.util.Assert;
 import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;

 import static com.sun.tools.javac.util.List.*;

 /**
  * Test harness whose goal is to simplify the task of writing type-system
  * regression test. It provides functionalities to build custom types as well
  * as to access the underlying javac's symbol table in order to retrieve
  * predefined types. Among the features supported by the harness are: type
  * substitution, type containment, subtyping, cast-conversion, assigment
  * conversion.
  *
  * This class is meant to be a common super class for all concrete type test
  * classes. A subclass can access the type-factory and the test methods so as
  * to write compact tests. An example is reported below:
  *
  * <pre>
  * Type X = fac.TypeVariable();
  * Type Y = fac.TypeVariable();
  * Type A_X_Y = fac.Class(0, X, Y);
  * Type A_Obj_Obj = fac.Class(0,
  *           predef.objectType,
  *           predef.objectType);
  * checkSameType(A_Obj_Obj, subst(A_X_Y,
  *           Mapping(X, predef.objectType),
  *           Mapping(Y, predef.objectType)));
  * </pre>
  *
  * The above code is used to create two class types, namely {@code A<X,Y>} and
  * {@code A<Object,Object>} where both {@code X} and {@code Y} are type-variables.
  * The code then verifies that {@code [X:=Object,Y:=Object]A<X,Y> == A<Object,Object>}.
  *
  * @author mcimadamore
  * @author vromero
  */
 public class TypeHarness {

     protected Types types;
     protected Check chk;
     protected Symtab predef;
     protected Names names;
     protected ReusableJavaCompiler tool;
     protected Infer infer;
     protected Context context;

     protected Factory fac;

     protected TypeHarness() {
         context = new Context();
         JavacFileManager.preRegister(context);
         MyAttr.preRegister(context);
         tool = new ReusableJavaCompiler(context);
         types = Types.instance(context);
         infer = Infer.instance(context);
         chk = Check.instance(context);
         predef = Symtab.instance(context);
         names = Names.instance(context);
         fac = new Factory();
     }

     // <editor-fold defaultstate="collapsed" desc="type assertions">

     /** assert that 's' is a subtype of 't' */
     public void assertSubtype(Type s, Type t) {
         assertSubtype(s, t, true);
     }

     /** assert that 's' is/is not a subtype of 't' */
     public void assertSubtype(Type s, Type t, boolean expected) {
         if (types.isSubtype(s, t) != expected) {
             String msg = expected ?
                 " is not a subtype of " :
                 " is a subtype of ";
             error(s + msg + t);
         }
     }

     /** assert that 's' is the same type as 't' */
     public void assertSameType(Type s, Type t) {
         assertSameType(s, t, true);
     }

     /** assert that 's' is/is not the same type as 't' */
     public void assertSameType(Type s, Type t, boolean expected) {
         if (types.isSameType(s, t) != expected) {
             String msg = expected ?
                 " is not the same type as " :
                 " is the same type as ";
             error(s + msg + t);
         }
     }

     /** assert that 's' is castable to 't' */
     public void assertCastable(Type s, Type t) {
         assertCastable(s, t, true);
     }

     /** assert that 's' is/is not castable to 't' */
     public void assertCastable(Type s, Type t, boolean expected) {
         if (types.isCastable(s, t) != expected) {
             String msg = expected ?
                 " is not castable to " :
                 " is castable to ";
             error(s + msg + t);
         }
     }

     /** assert that 's' is convertible (method invocation conversion) to 't' */
     public void assertConvertible(Type s, Type t) {
         assertCastable(s, t, true);
     }

     /** assert that 's' is/is not convertible (method invocation conversion) to 't' */
     public void assertConvertible(Type s, Type t, boolean expected) {
         if (types.isConvertible(s, t) != expected) {
             String msg = expected ?
                 " is not convertible to " :
                 " is convertible to ";
             error(s + msg + t);
         }
     }

     /** assert that 's' is assignable to 't' */
     public void assertAssignable(Type s, Type t) {
         assertCastable(s, t, true);
     }

     /** assert that 's' is/is not assignable to 't' */
     public void assertAssignable(Type s, Type t, boolean expected) {
         if (types.isAssignable(s, t) != expected) {
             String msg = expected ?
                 " is not assignable to " :
                 " is assignable to ";
             error(s + msg + t);
         }
     }

     /** assert that generic type 't' is well-formed */
     public void assertValidGenericType(Type t) {
         assertValidGenericType(t, true);
     }

     /** assert that 's' is/is not assignable to 't' */
     public void assertValidGenericType(Type t, boolean expected) {
         if (chk.checkValidGenericType(t) != expected) {
             String msg = expected ?
                 " is not a valid generic type" :
                 " is a valid generic type";
             error(t + msg + "   " + t.tsym.type);
         }
     }
     // </editor-fold>

     /** Creates an inference context given a list of type variables and performs the given action on it.
      *  The intention is to provide a way to do unit testing on inference contexts.
      *  @param typeVars  a list of type variables to create the inference context from
      *  @param consumer  the action to be performed on the inference context
      */
     protected void withInferenceContext(List<Type> typeVars, Consumer<InferenceContext> consumer) {
         Assert.check(!typeVars.isEmpty(), "invalid parameter, empty type variables list");
         ListBuffer undetVarsBuffer = new ListBuffer();
         typeVars.stream().map((tv) -> new UndetVar((TypeVar)tv, null, types)).forEach((undetVar) -> {
             undetVarsBuffer.add(undetVar);
         });
         List<Type> undetVarsList = undetVarsBuffer.toList();
         InferenceContext inferenceContext = new InferenceContext(infer, nil(), undetVarsList);
         inferenceContext.rollback(undetVarsList);
         consumer.accept(inferenceContext);
     }

     private void error(String msg) {
         throw new AssertionError("Unexpected result: " + msg);
     }

     // <editor-fold defaultstate="collapsed" desc="type functions">

     /** compute the erasure of a type 't' */
     public Type erasure(Type t) {
         return types.erasure(t);
     }

     /** compute the capture of a type 't' */
     public Type capture(Type t) {
         return types.capture(t);
     }

     /** compute the boxed type associated with 't' */
     public Type box(Type t) {
         if (!t.isPrimitive()) {
             throw new AssertionError("Cannot box non-primitive type: " + t);
         }
         return types.boxedClass(t).type;
     }

     /** compute the unboxed type associated with 't' */
     public Type unbox(Type t) {
         Type u = types.unboxedType(t);
         if (t == null) {
             throw new AssertionError("Cannot unbox reference type: " + t);
         } else {
             return u;
         }
     }

     /** compute a type substitution on 't' given a list of type mappings */
     public Type subst(Type t, Mapping... maps) {
         ListBuffer<Type> from = new ListBuffer<>();
         ListBuffer<Type> to = new ListBuffer<>();
         for (Mapping tm : maps) {
             from.append(tm.from);
             to.append(tm.to);
         }
         return types.subst(t, from.toList(), to.toList());
     }

     /** create a fresh type mapping from a type to another */
     public Mapping Mapping(Type from, Type to) {
         return new Mapping(from, to);
     }

     public static class Mapping {
         Type from;
         Type to;
         private Mapping(Type from, Type to) {
             this.from = from;
             this.to = to;
         }
     }
     // </editor-fold>

     // <editor-fold defaultstate="collapsed" desc="type factory">

     /**
      * This class is used to create Java types in a simple way. All main
      * kinds of type are supported: primitive, reference, non-denotable. The
      * factory also supports creation of constant types (used by the compiler
      * to represent the type of a literal).
      */
     public class Factory {

         private int synthNameCount = 0;

         private Name syntheticName() {
             return names.fromString("A$" + synthNameCount++);
         }

         public ClassType Class(long flags, Type... typeArgs) {
             ClassSymbol csym = new ClassSymbol(flags, syntheticName(), predef.noSymbol);
             csym.type = new ClassType(Type.noType, List.from(typeArgs), csym);
             ((ClassType)csym.type).supertype_field = predef.objectType;
             return (ClassType)csym.type;
         }

         public ClassType Class(Type... typeArgs) {
             return Class(0, typeArgs);
         }

         public ClassType Interface(Type... typeArgs) {
             return Class(Flags.INTERFACE, typeArgs);
         }

         public ClassType Interface(long flags, Type... typeArgs) {
             return Class(Flags.INTERFACE | flags, typeArgs);
         }

         public Type Constant(byte b) {
             return predef.byteType.constType(b);
         }

         public Type Constant(short s) {
             return predef.shortType.constType(s);
         }

         public Type Constant(int i) {
             return predef.intType.constType(i);
         }

         public Type Constant(long l) {
             return predef.longType.constType(l);
         }

         public Type Constant(float f) {
             return predef.floatType.constType(f);
         }

         public Type Constant(double d) {
             return predef.doubleType.constType(d);
         }

         public Type Constant(char c) {
             return predef.charType.constType(c + 0);
         }

         public ArrayType Array(Type elemType) {
             return new ArrayType(elemType, predef.arrayClass);
         }

         public TypeVar TypeVariable() {
             return TypeVariable(predef.objectType);
         }

         public TypeVar TypeVariable(Type bound) {
             TypeSymbol tvsym = new TypeVariableSymbol(0, syntheticName(), null, predef.noSymbol);
             tvsym.type = new TypeVar(tvsym, bound, Type.noType);
             return (TypeVar)tvsym.type;
         }

         public WildcardType Wildcard(BoundKind bk, Type bound) {
             return new WildcardType(bound, bk, predef.boundClass);
         }

         public CapturedType CapturedVariable(Type upper, Type lower) {
             return new CapturedType(syntheticName(), predef.noSymbol, upper, lower, null);
         }

         public ClassType Intersection(Type classBound, Type... intfBounds) {
             ClassType ct = Class(Flags.COMPOUND);
             ct.supertype_field = classBound;
             ct.interfaces_field = List.from(intfBounds);
             return ct;
         }
     }
     // </editor-fold>

     // <editor-fold defaultstate="collapsed" desc="StrToTypeFactory">
     /**
      * StrToTypeFactory is a class provided to ease the creation of complex types from Strings.
      * The client code can specify a package, a list of imports and a list of type variables when
      * creating an instance of StrToTypeFactory. Later types including, or not, these type variables
      * can be created by the factory. All occurrences of the same type variable in a type defined
      * using a String are guaranteed to refer to the same type variable in the created type.
      *
      * An example is reported below:
      *
      * <pre>
      * List<String> imports = new ArrayList<>();
      * imports.add("java.util.*");
      * List<String> typeVars = new ArrayList<>();
      * typeVars.add("T");
      * strToTypeFactory = new StrToTypeFactory(null, imports, typeVars);
      *
      * Type freeType = strToTypeFactory.getType("List<? extends T>");
      * Type aType = strToTypeFactory.getType("List<? extends String>");
      *
      * // method withInferenceContext() belongs to TypeHarness
      * withInferenceContext(strToTypeFactory.getTypeVars(), inferenceContext -> {
      *     assertSameType(inferenceContext.asUndetVar(freeType), aType);
      *     UndetVar undetVarForT = (UndetVar)inferenceContext.undetVars().head;
      *     com.sun.tools.javac.util.List<Type> equalBounds = undetVarForT.getBounds(InferenceBound.EQ);
      *     Assert.check(!equalBounds.isEmpty() && equalBounds.length() == 1,
      *          "undetVar must have only one equality bound");
      * });
      * </pre>
      */
     public class StrToTypeFactory {
         int id = 0;
         String pkg;
         java.util.List<String> imports;
         public java.util.List<String> typeVarDecls;
         public List<Type> typeVariables;

         public StrToTypeFactory(String pkg, java.util.List<String> imports, java.util.List<String> typeVarDecls) {
             this.pkg = pkg;
             this.imports = imports;
             this.typeVarDecls = typeVarDecls == null ? new ArrayList<>() : typeVarDecls;
             this.typeVariables = from(this.typeVarDecls.stream()
                     .map(this::typeVarName)
                     .map(this::getType)
                     .collect(Collectors.toList())
             );
         }

         TypeVar getTypeVarFromStr(String name) {
             if (typeVarDecls.isEmpty()) {
                 return null;
             }
             int index = typeVarDecls.indexOf(name);
             if (index != -1) {
                 return (TypeVar)typeVariables.get(index);
             }
             return null;
         }

         List<Type> getTypeVars() {
             return typeVariables;
         }

         String typeVarName(String typeVarDecl) {
             String[] ss = typeVarDecl.split(" ");
             return ss[0];
         }

         public final Type getType(String type) {
             JavaSource source = new JavaSource(type);
             MyAttr.theType = null;
             MyAttr.typeParameters = List.nil();
             tool.clear();
             List<JavaFileObject> inputs = of(source);
             try {
                 tool.compile(inputs);
             } catch (Throwable ex) {
                 throw new Abort(ex);
             }
             if (typeVariables != null) {
                 return types.subst(MyAttr.theType, MyAttr.typeParameters, typeVariables);
             }
             return MyAttr.theType;
         }

         class JavaSource extends SimpleJavaFileObject {

             String id;
             String type;
             String template = "#Package;\n" +
                     "#Imports\n" +
                     "class G#Id#TypeVars {\n" +
                     "   #FieldType var;" +
                     "}";

             JavaSource(String type) {
                 super(URI.create("myfo:/Test.java"), JavaFileObject.Kind.SOURCE);
                 this.id = String.valueOf(StrToTypeFactory.this.id++);
                 this.type = type;
             }

             @Override
             public CharSequence getCharContent(boolean ignoreEncodingErrors) {
                 String impStmts = imports.size() > 0 ?
                         imports.stream().map(i -> "import " + i + ";").collect(Collectors.joining("\n")) : "";
                 String tvars = !typeVarDecls.isEmpty() ?
                         typeVarDecls.stream().collect(Collectors.joining(",", "<", ">")) : "";
                 return template
                         .replace("#Package", (pkg == null) ? "" : "package " + pkg + ";")
                         .replace("#Imports", impStmts)
                         .replace("#Id", id)
                         .replace("#TypeVars", tvars)
                         .replace("#FieldType", type);
             }
         }
     }
     // </editor-fold>

     // <editor-fold defaultstate="collapsed" desc="helper classes">
     static class MyAttr extends Attr {

         private static Type theType;
         private static List<Type> typeParameters = List.nil();

         static void preRegister(Context context) {
             context.put(attrKey, (com.sun.tools.javac.util.Context.Factory<Attr>) c -> new MyAttr(c));
         }

         MyAttr(Context context) {
             super(context);
         }

         @Override
         public void visitVarDef(JCVariableDecl tree) {
             super.visitVarDef(tree);
             theType = tree.type;
         }

         @Override
         public void attribClass(DiagnosticPosition pos, ClassSymbol c) {
             super.attribClass(pos, c);
             ClassType ct = (ClassType)c.type;
             typeParameters = ct.typarams_field;
         }
     }

     static class ReusableJavaCompiler extends JavaCompiler {
         ReusableJavaCompiler(Context context) {
             super(context);
         }

         @Override
         protected void checkReusable() {
             // do nothing
         }

         @Override
         public void close() {
             //do nothing
         }

         void clear() {
             newRound();
             Modules.instance(context).newRound();
         }
     }
     // </editor-fold>
 }
	/*
	* Copyright (c) 2010, 2016, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	import java.net.URI;
	import java.util.ArrayList;
	import java.util.function.Consumer;
	import java.util.stream.Collectors;

	import javax.tools.JavaFileObject;
	import javax.tools.SimpleJavaFileObject;

	import com.sun.tools.javac.code.BoundKind;
	import com.sun.tools.javac.code.Flags;
	import com.sun.tools.javac.util.Context;
	import com.sun.tools.javac.code.Types;
	import com.sun.tools.javac.code.Symtab;
	import com.sun.tools.javac.code.Type;
	import com.sun.tools.javac.code.Type.*;
	import com.sun.tools.javac.code.Symbol.*;
	import com.sun.tools.javac.comp.Attr;
	import com.sun.tools.javac.comp.Check;
	import com.sun.tools.javac.comp.Infer;
	import com.sun.tools.javac.comp.InferenceContext;
	import com.sun.tools.javac.comp.Modules;
	import com.sun.tools.javac.util.List;
	import com.sun.tools.javac.util.ListBuffer;
	import com.sun.tools.javac.util.Name;
	import com.sun.tools.javac.util.Names;
	import com.sun.tools.javac.file.JavacFileManager;
	import com.sun.tools.javac.main.JavaCompiler;
	import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
	import com.sun.tools.javac.util.Abort;
	import com.sun.tools.javac.util.Assert;
	import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;

	import static com.sun.tools.javac.util.List.*;

	/**
	* Test harness whose goal is to simplify the task of writing type-system
	* regression test. It provides functionalities to build custom types as well
	* as to access the underlying javac's symbol table in order to retrieve
	* predefined types. Among the features supported by the harness are: type
	* substitution, type containment, subtyping, cast-conversion, assigment
	* conversion.
	*
	* This class is meant to be a common super class for all concrete type test
	* classes. A subclass can access the type-factory and the test methods so as
	* to write compact tests. An example is reported below:
	*
	* <pre>
	* Type X = fac.TypeVariable();
	* Type Y = fac.TypeVariable();
	* Type A_X_Y = fac.Class(0, X, Y);
	* Type A_Obj_Obj = fac.Class(0,
	* predef.objectType,
	* predef.objectType);
	* checkSameType(A_Obj_Obj, subst(A_X_Y,
	* Mapping(X, predef.objectType),
	* Mapping(Y, predef.objectType)));
	* </pre>
	*
	* The above code is used to create two class types, namely {@code A<X,Y>} and
	* {@code A<Object,Object>} where both {@code X} and {@code Y} are type-variables.
	* The code then verifies that {@code [X:=Object,Y:=Object]A<X,Y> == A<Object,Object>}.
	*
	* @author mcimadamore
	* @author vromero
	*/
	public class TypeHarness {

	protected Types types;
	protected Check chk;
	protected Symtab predef;
	protected Names names;
	protected ReusableJavaCompiler tool;
	protected Infer infer;
	protected Context context;

	protected Factory fac;

	protected TypeHarness() {
	context = new Context();
	JavacFileManager.preRegister(context);
	MyAttr.preRegister(context);
	tool = new ReusableJavaCompiler(context);
	types = Types.instance(context);
	infer = Infer.instance(context);
	chk = Check.instance(context);
	predef = Symtab.instance(context);
	names = Names.instance(context);
	fac = new Factory();
	}

	// <editor-fold defaultstate="collapsed" desc="type assertions">

	/** assert that 's' is a subtype of 't' */
	public void assertSubtype(Type s, Type t) {
	assertSubtype(s, t, true);
	}

	/** assert that 's' is/is not a subtype of 't' */
	public void assertSubtype(Type s, Type t, boolean expected) {
	if (types.isSubtype(s, t) != expected) {
	String msg = expected ?
	" is not a subtype of " :
	" is a subtype of ";
	error(s + msg + t);
	}
	}

	/** assert that 's' is the same type as 't' */
	public void assertSameType(Type s, Type t) {
	assertSameType(s, t, true);
	}

	/** assert that 's' is/is not the same type as 't' */
	public void assertSameType(Type s, Type t, boolean expected) {
	if (types.isSameType(s, t) != expected) {
	String msg = expected ?
	" is not the same type as " :
	" is the same type as ";
	error(s + msg + t);
	}
	}

	/** assert that 's' is castable to 't' */
	public void assertCastable(Type s, Type t) {
	assertCastable(s, t, true);
	}

	/** assert that 's' is/is not castable to 't' */
	public void assertCastable(Type s, Type t, boolean expected) {
	if (types.isCastable(s, t) != expected) {
	String msg = expected ?
	" is not castable to " :
	" is castable to ";
	error(s + msg + t);
	}
	}

	/** assert that 's' is convertible (method invocation conversion) to 't' */
	public void assertConvertible(Type s, Type t) {
	assertCastable(s, t, true);
	}

	/** assert that 's' is/is not convertible (method invocation conversion) to 't' */
	public void assertConvertible(Type s, Type t, boolean expected) {
	if (types.isConvertible(s, t) != expected) {
	String msg = expected ?
	" is not convertible to " :
	" is convertible to ";
	error(s + msg + t);
	}
	}

	/** assert that 's' is assignable to 't' */
	public void assertAssignable(Type s, Type t) {
	assertCastable(s, t, true);
	}

	/** assert that 's' is/is not assignable to 't' */
	public void assertAssignable(Type s, Type t, boolean expected) {
	if (types.isAssignable(s, t) != expected) {
	String msg = expected ?
	" is not assignable to " :
	" is assignable to ";
	error(s + msg + t);
	}
	}

	/** assert that generic type 't' is well-formed */
	public void assertValidGenericType(Type t) {
	assertValidGenericType(t, true);
	}

	/** assert that 's' is/is not assignable to 't' */
	public void assertValidGenericType(Type t, boolean expected) {
	if (chk.checkValidGenericType(t) != expected) {
	String msg = expected ?
	" is not a valid generic type" :
	" is a valid generic type";
	error(t + msg + " " + t.tsym.type);
	}
	}
	// </editor-fold>

	/** Creates an inference context given a list of type variables and performs the given action on it.
	* The intention is to provide a way to do unit testing on inference contexts.
	* @param typeVars a list of type variables to create the inference context from
	* @param consumer the action to be performed on the inference context
	*/
	protected void withInferenceContext(List<Type> typeVars, Consumer<InferenceContext> consumer) {
	Assert.check(!typeVars.isEmpty(), "invalid parameter, empty type variables list");
	ListBuffer undetVarsBuffer = new ListBuffer();
	typeVars.stream().map((tv) -> new UndetVar((TypeVar)tv, null, types)).forEach((undetVar) -> {
	undetVarsBuffer.add(undetVar);
	});
	List<Type> undetVarsList = undetVarsBuffer.toList();
	InferenceContext inferenceContext = new InferenceContext(infer, nil(), undetVarsList);
	inferenceContext.rollback(undetVarsList);
	consumer.accept(inferenceContext);
	}

	private void error(String msg) {
	throw new AssertionError("Unexpected result: " + msg);
	}

	// <editor-fold defaultstate="collapsed" desc="type functions">

	/** compute the erasure of a type 't' */
	public Type erasure(Type t) {
	return types.erasure(t);
	}

	/** compute the capture of a type 't' */
	public Type capture(Type t) {
	return types.capture(t);
	}

	/** compute the boxed type associated with 't' */
	public Type box(Type t) {
	if (!t.isPrimitive()) {
	throw new AssertionError("Cannot box non-primitive type: " + t);
	}
	return types.boxedClass(t).type;
	}

	/** compute the unboxed type associated with 't' */
	public Type unbox(Type t) {
	Type u = types.unboxedType(t);
	if (t == null) {
	throw new AssertionError("Cannot unbox reference type: " + t);
	} else {
	return u;
	}
	}

	/** compute a type substitution on 't' given a list of type mappings */
	public Type subst(Type t, Mapping... maps) {
	ListBuffer<Type> from = new ListBuffer<>();
	ListBuffer<Type> to = new ListBuffer<>();
	for (Mapping tm : maps) {
	from.append(tm.from);
	to.append(tm.to);
	}
	return types.subst(t, from.toList(), to.toList());
	}

	/** create a fresh type mapping from a type to another */
	public Mapping Mapping(Type from, Type to) {
	return new Mapping(from, to);
	}

	public static class Mapping {
	Type from;
	Type to;
	private Mapping(Type from, Type to) {
	this.from = from;
	this.to = to;
	}
	}
	// </editor-fold>

	// <editor-fold defaultstate="collapsed" desc="type factory">

	/**
	* This class is used to create Java types in a simple way. All main
	* kinds of type are supported: primitive, reference, non-denotable. The
	* factory also supports creation of constant types (used by the compiler
	* to represent the type of a literal).
	*/
	public class Factory {

	private int synthNameCount = 0;

	private Name syntheticName() {
	return names.fromString("A$" + synthNameCount++);
	}

	public ClassType Class(long flags, Type... typeArgs) {
	ClassSymbol csym = new ClassSymbol(flags, syntheticName(), predef.noSymbol);
	csym.type = new ClassType(Type.noType, List.from(typeArgs), csym);
	((ClassType)csym.type).supertype_field = predef.objectType;
	return (ClassType)csym.type;
	}

	public ClassType Class(Type... typeArgs) {
	return Class(0, typeArgs);
	}

	public ClassType Interface(Type... typeArgs) {
	return Class(Flags.INTERFACE, typeArgs);
	}

	public ClassType Interface(long flags, Type... typeArgs) {
	return Class(Flags.INTERFACE \| flags, typeArgs);
	}

	public Type Constant(byte b) {
	return predef.byteType.constType(b);
	}

	public Type Constant(short s) {
	return predef.shortType.constType(s);
	}

	public Type Constant(int i) {
	return predef.intType.constType(i);
	}

	public Type Constant(long l) {
	return predef.longType.constType(l);
	}

	public Type Constant(float f) {
	return predef.floatType.constType(f);
	}

	public Type Constant(double d) {
	return predef.doubleType.constType(d);
	}

	public Type Constant(char c) {
	return predef.charType.constType(c + 0);
	}

	public ArrayType Array(Type elemType) {
	return new ArrayType(elemType, predef.arrayClass);
	}

	public TypeVar TypeVariable() {
	return TypeVariable(predef.objectType);
	}

	public TypeVar TypeVariable(Type bound) {
	TypeSymbol tvsym = new TypeVariableSymbol(0, syntheticName(), null, predef.noSymbol);
	tvsym.type = new TypeVar(tvsym, bound, Type.noType);
	return (TypeVar)tvsym.type;
	}

	public WildcardType Wildcard(BoundKind bk, Type bound) {
	return new WildcardType(bound, bk, predef.boundClass);
	}

	public CapturedType CapturedVariable(Type upper, Type lower) {
	return new CapturedType(syntheticName(), predef.noSymbol, upper, lower, null);
	}

	public ClassType Intersection(Type classBound, Type... intfBounds) {
	ClassType ct = Class(Flags.COMPOUND);
	ct.supertype_field = classBound;
	ct.interfaces_field = List.from(intfBounds);
	return ct;
	}
	}
	// </editor-fold>

	// <editor-fold defaultstate="collapsed" desc="StrToTypeFactory">
	/**
	* StrToTypeFactory is a class provided to ease the creation of complex types from Strings.
	* The client code can specify a package, a list of imports and a list of type variables when
	* creating an instance of StrToTypeFactory. Later types including, or not, these type variables
	* can be created by the factory. All occurrences of the same type variable in a type defined
	* using a String are guaranteed to refer to the same type variable in the created type.
	*
	* An example is reported below:
	*
	* <pre>
	* List<String> imports = new ArrayList<>();
	* imports.add("java.util.*");
	* List<String> typeVars = new ArrayList<>();
	* typeVars.add("T");
	* strToTypeFactory = new StrToTypeFactory(null, imports, typeVars);
	*
	* Type freeType = strToTypeFactory.getType("List<? extends T>");
	* Type aType = strToTypeFactory.getType("List<? extends String>");
	*
	* // method withInferenceContext() belongs to TypeHarness
	* withInferenceContext(strToTypeFactory.getTypeVars(), inferenceContext -> {
	* assertSameType(inferenceContext.asUndetVar(freeType), aType);
	* UndetVar undetVarForT = (UndetVar)inferenceContext.undetVars().head;
	* com.sun.tools.javac.util.List<Type> equalBounds = undetVarForT.getBounds(InferenceBound.EQ);
	* Assert.check(!equalBounds.isEmpty() && equalBounds.length() == 1,
	* "undetVar must have only one equality bound");
	* });
	* </pre>
	*/
	public class StrToTypeFactory {
	int id = 0;
	String pkg;
	java.util.List<String> imports;
	public java.util.List<String> typeVarDecls;
	public List<Type> typeVariables;

	public StrToTypeFactory(String pkg, java.util.List<String> imports, java.util.List<String> typeVarDecls) {
	this.pkg = pkg;
	this.imports = imports;
	this.typeVarDecls = typeVarDecls == null ? new ArrayList<>() : typeVarDecls;
	this.typeVariables = from(this.typeVarDecls.stream()
	.map(this::typeVarName)
	.map(this::getType)
	.collect(Collectors.toList())
	);
	}

	TypeVar getTypeVarFromStr(String name) {
	if (typeVarDecls.isEmpty()) {
	return null;
	}
	int index = typeVarDecls.indexOf(name);
	if (index != -1) {
	return (TypeVar)typeVariables.get(index);
	}
	return null;
	}

	List<Type> getTypeVars() {
	return typeVariables;
	}

	String typeVarName(String typeVarDecl) {
	String[] ss = typeVarDecl.split(" ");
	return ss[0];
	}

	public final Type getType(String type) {
	JavaSource source = new JavaSource(type);
	MyAttr.theType = null;
	MyAttr.typeParameters = List.nil();
	tool.clear();
	List<JavaFileObject> inputs = of(source);
	try {
	tool.compile(inputs);
	} catch (Throwable ex) {
	throw new Abort(ex);
	}
	if (typeVariables != null) {
	return types.subst(MyAttr.theType, MyAttr.typeParameters, typeVariables);
	}
	return MyAttr.theType;
	}

	class JavaSource extends SimpleJavaFileObject {

	String id;
	String type;
	String template = "#Package;\n" +
	"#Imports\n" +
	"class G#Id#TypeVars {\n" +
	" #FieldType var;" +
	"}";

	JavaSource(String type) {
	super(URI.create("myfo:/Test.java"), JavaFileObject.Kind.SOURCE);
	this.id = String.valueOf(StrToTypeFactory.this.id++);
	this.type = type;
	}

	@Override
	public CharSequence getCharContent(boolean ignoreEncodingErrors) {
	String impStmts = imports.size() > 0 ?
	imports.stream().map(i -> "import " + i + ";").collect(Collectors.joining("\n")) : "";
	String tvars = !typeVarDecls.isEmpty() ?
	typeVarDecls.stream().collect(Collectors.joining(",", "<", ">")) : "";
	return template
	.replace("#Package", (pkg == null) ? "" : "package " + pkg + ";")
	.replace("#Imports", impStmts)
	.replace("#Id", id)
	.replace("#TypeVars", tvars)
	.replace("#FieldType", type);
	}
	}
	}
	// </editor-fold>

	// <editor-fold defaultstate="collapsed" desc="helper classes">
	static class MyAttr extends Attr {

	private static Type theType;
	private static List<Type> typeParameters = List.nil();

	static void preRegister(Context context) {
	context.put(attrKey, (com.sun.tools.javac.util.Context.Factory<Attr>) c -> new MyAttr(c));
	}

	MyAttr(Context context) {
	super(context);
	}

	@Override
	public void visitVarDef(JCVariableDecl tree) {
	super.visitVarDef(tree);
	theType = tree.type;
	}

	@Override
	public void attribClass(DiagnosticPosition pos, ClassSymbol c) {
	super.attribClass(pos, c);
	ClassType ct = (ClassType)c.type;
	typeParameters = ct.typarams_field;
	}
	}

	static class ReusableJavaCompiler extends JavaCompiler {
	ReusableJavaCompiler(Context context) {
	super(context);
	}

	@Override
	protected void checkReusable() {
	// do nothing
	}

	@Override
	public void close() {
	//do nothing
	}

	void clear() {
	newRound();
	Modules.instance(context).newRound();
	}
	}
	// </editor-fold>
	}