repo/org.ibex.tool/src/org/eclipse/jdt/internal/compiler/ast/Expression.java

   1 /*******************************************************************************
   2  * Copyright (c) 2000, 2004 IBM Corporation and others.
   3  * All rights reserved. This program and the accompanying materials
   4  * are made available under the terms of the Common Public License v1.0
   5  * which accompanies this distribution, and is available at
   6  * http://www.eclipse.org/legal/cpl-v10.html
   7  *
   8  * Contributors:
   9  *     IBM Corporation - initial API and implementation
  10  *******************************************************************************/
  11 package org.eclipse.jdt.internal.compiler.ast;
  12
  13 import org.eclipse.jdt.internal.compiler.impl.*;
  14 import org.eclipse.jdt.internal.compiler.codegen.*;
  15 import org.eclipse.jdt.internal.compiler.flow.*;
  16 import org.eclipse.jdt.internal.compiler.lookup.*;
  17 import org.eclipse.jdt.internal.compiler.problem.*;
  18 import org.eclipse.jdt.internal.compiler.util.Util;
  19
  20 public abstract class Expression extends Statement {
  21
  22         //Some expression may not be used - from a java semantic point
  23         //of view only - as statements. Other may. In order to avoid the creation
  24         //of wrappers around expression in order to tune them as expression
  25         //Expression is a subclass of Statement. See the message isValidJavaStatement()
  26
  27         public int implicitConversion;
  28         public TypeBinding resolvedType;
  29
  30         public Constant constant;
  31
  32         public Expression() {
  33                 super();
  34         }
  35
  36         public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
  37
  38                 return flowInfo;
  39         }
  40
  41         public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo, boolean valueRequired) {
  42
  43                 return analyseCode(currentScope, flowContext, flowInfo);
  44         }
  45
  46         /**
  47          * Constant usable for bytecode pattern optimizations, but cannot be inlined
  48          * since it is not strictly equivalent to the definition of constant expressions.
  49          * In particular, some side-effects may be required to occur (only the end value
  50          * is known).
  51          * @return Constant known to be of boolean type
  52          */
  53         public Constant optimizedBooleanConstant() {
  54                 return this.constant;
  55         }
  56
  57         public static final boolean isConstantValueRepresentable(
  58                 Constant constant,
  59                 int constantTypeID,
  60                 int targetTypeID) {
  61
  62                 //true if there is no loss of precision while casting.
  63                 // constantTypeID == constant.typeID
  64                 if (targetTypeID == constantTypeID)
  65                         return true;
  66                 switch (targetTypeID) {
  67                         case T_char :
  68                                 switch (constantTypeID) {
  69                                         case T_char :
  70                                                 return true;
  71                                         case T_double :
  72                                                 return constant.doubleValue() == constant.charValue();
  73                                         case T_float :
  74                                                 return constant.floatValue() == constant.charValue();
  75                                         case T_int :
  76                                                 return constant.intValue() == constant.charValue();
  77                                         case T_short :
  78                                                 return constant.shortValue() == constant.charValue();
  79                                         case T_byte :
  80                                                 return constant.byteValue() == constant.charValue();
  81                                         case T_long :
  82                                                 return constant.longValue() == constant.charValue();
  83                                         default :
  84                                                 return false;//boolean
  85                                 }
  86
  87                         case T_float :
  88                                 switch (constantTypeID) {
  89                                         case T_char :
  90                                                 return constant.charValue() == constant.floatValue();
  91                                         case T_double :
  92                                                 return constant.doubleValue() == constant.floatValue();
  93                                         case T_float :
  94                                                 return true;
  95                                         case T_int :
  96                                                 return constant.intValue() == constant.floatValue();
  97                                         case T_short :
  98                                                 return constant.shortValue() == constant.floatValue();
  99                                         case T_byte :
 100                                                 return constant.byteValue() == constant.floatValue();
 101                                         case T_long :
 102                                                 return constant.longValue() == constant.floatValue();
 103                                         default :
 104                                                 return false;//boolean
 105                                 }
 106
 107                         case T_double :
 108                                 switch (constantTypeID) {
 109                                         case T_char :
 110                                                 return constant.charValue() == constant.doubleValue();
 111                                         case T_double :
 112                                                 return true;
 113                                         case T_float :
 114                                                 return constant.floatValue() == constant.doubleValue();
 115                                         case T_int :
 116                                                 return constant.intValue() == constant.doubleValue();
 117                                         case T_short :
 118                                                 return constant.shortValue() == constant.doubleValue();
 119                                         case T_byte :
 120                                                 return constant.byteValue() == constant.doubleValue();
 121                                         case T_long :
 122                                                 return constant.longValue() == constant.doubleValue();
 123                                         default :
 124                                                 return false; //boolean
 125                                 }
 126
 127                         case T_byte :
 128                                 switch (constantTypeID) {
 129                                         case T_char :
 130                                                 return constant.charValue() == constant.byteValue();
 131                                         case T_double :
 132                                                 return constant.doubleValue() == constant.byteValue();
 133                                         case T_float :
 134                                                 return constant.floatValue() == constant.byteValue();
 135                                         case T_int :
 136                                                 return constant.intValue() == constant.byteValue();
 137                                         case T_short :
 138                                                 return constant.shortValue() == constant.byteValue();
 139                                         case T_byte :
 140                                                 return true;
 141                                         case T_long :
 142                                                 return constant.longValue() == constant.byteValue();
 143                                         default :
 144                                                 return false; //boolean
 145                                 }
 146
 147                         case T_short :
 148                                 switch (constantTypeID) {
 149                                         case T_char :
 150                                                 return constant.charValue() == constant.shortValue();
 151                                         case T_double :
 152                                                 return constant.doubleValue() == constant.shortValue();
 153                                         case T_float :
 154                                                 return constant.floatValue() == constant.shortValue();
 155                                         case T_int :
 156                                                 return constant.intValue() == constant.shortValue();
 157                                         case T_short :
 158                                                 return true;
 159                                         case T_byte :
 160                                                 return constant.byteValue() == constant.shortValue();
 161                                         case T_long :
 162                                                 return constant.longValue() == constant.shortValue();
 163                                         default :
 164                                                 return false; //boolean
 165                                 }
 166
 167                         case T_int :
 168                                 switch (constantTypeID) {
 169                                         case T_char :
 170                                                 return constant.charValue() == constant.intValue();
 171                                         case T_double :
 172                                                 return constant.doubleValue() == constant.intValue();
 173                                         case T_float :
 174                                                 return constant.floatValue() == constant.intValue();
 175                                         case T_int :
 176                                                 return true;
 177                                         case T_short :
 178                                                 return constant.shortValue() == constant.intValue();
 179                                         case T_byte :
 180                                                 return constant.byteValue() == constant.intValue();
 181                                         case T_long :
 182                                                 return constant.longValue() == constant.intValue();
 183                                         default :
 184                                                 return false; //boolean
 185                                 }
 186
 187                         case T_long :
 188                                 switch (constantTypeID) {
 189                                         case T_char :
 190                                                 return constant.charValue() == constant.longValue();
 191                                         case T_double :
 192                                                 return constant.doubleValue() == constant.longValue();
 193                                         case T_float :
 194                                                 return constant.floatValue() == constant.longValue();
 195                                         case T_int :
 196                                                 return constant.intValue() == constant.longValue();
 197                                         case T_short :
 198                                                 return constant.shortValue() == constant.longValue();
 199                                         case T_byte :
 200                                                 return constant.byteValue() == constant.longValue();
 201                                         case T_long :
 202                                                 return true;
 203                                         default :
 204                                                 return false; //boolean
 205                                 }
 206
 207                         default :
 208                                 return false; //boolean
 209                 }
 210         }
 211
 212         /**
 213          * Expression statements are plain expressions, however they generate like
 214          * normal expressions with no value required.
 215          *
 216          * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
 217          * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
 218          */
 219         public void generateCode(BlockScope currentScope, CodeStream codeStream) {
 220
 221                 if ((bits & IsReachableMASK) == 0) {
 222                         return;
 223                 }
 224                 generateCode(currentScope, codeStream, false);
 225         }
 226
 227         /**
 228          * Every expression is responsible for generating its implicit conversion when necessary.
 229          *
 230          * @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
 231          * @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
 232          * @param valueRequired boolean
 233          */
 234         public void generateCode(
 235                 BlockScope currentScope,
 236                 CodeStream codeStream,
 237                 boolean valueRequired) {
 238
 239                 if (constant != NotAConstant) {
 240                         // generate a constant expression
 241                         int pc = codeStream.position;
 242                         codeStream.generateConstant(constant, implicitConversion);
 243                         codeStream.recordPositionsFrom(pc, this.sourceStart);
 244                 } else {
 245                         // actual non-constant code generation
 246                         throw new ShouldNotImplement(Util.bind("ast.missingCode")); //$NON-NLS-1$
 247                 }
 248         }
 249
 250         /**
 251          * Default generation of a boolean value
 252          * @param currentScope
 253          * @param codeStream
 254          * @param trueLabel
 255          * @param falseLabel
 256          * @param valueRequired
 257          */
 258         public void generateOptimizedBoolean(
 259                 BlockScope currentScope,
 260                 CodeStream codeStream,
 261                 Label trueLabel,
 262                 Label falseLabel,
 263                 boolean valueRequired) {
 264
 265                 // a label valued to nil means: by default we fall through the case...
 266                 // both nil means we leave the value on the stack
 267
 268                 if ((constant != Constant.NotAConstant) && (constant.typeID() == T_boolean)) {
 269                         int pc = codeStream.position;
 270                         if (constant.booleanValue() == true) {
 271                                 // constant == true
 272                                 if (valueRequired) {
 273                                         if (falseLabel == null) {
 274                                                 // implicit falling through the FALSE case
 275                                                 if (trueLabel != null) {
 276                                                         codeStream.goto_(trueLabel);
 277                                                 }
 278                                         }
 279                                 }
 280                         } else {
 281                                 if (valueRequired) {
 282                                         if (falseLabel != null) {
 283                                                 // implicit falling through the TRUE case
 284                                                 if (trueLabel == null) {
 285                                                         codeStream.goto_(falseLabel);
 286                                                 }
 287                                         }
 288                                 }
 289                         }
 290                         codeStream.recordPositionsFrom(pc, this.sourceStart);
 291                         return;
 292                 }
 293                 generateCode(currentScope, codeStream, valueRequired);
 294                 // branching
 295                 int position = codeStream.position;
 296                 if (valueRequired) {
 297                         if (falseLabel == null) {
 298                                 if (trueLabel != null) {
 299                                         // Implicit falling through the FALSE case
 300                                         codeStream.ifne(trueLabel);
 301                                 }
 302                         } else {
 303                                 if (trueLabel == null) {
 304                                         // Implicit falling through the TRUE case
 305                                         codeStream.ifeq(falseLabel);
 306                                 } else {
 307                                         // No implicit fall through TRUE/FALSE --> should never occur
 308                                 }
 309                         }
 310                 }
 311                 // reposition the endPC
 312                 codeStream.updateLastRecordedEndPC(position);
 313         }
 314
 315         /* Optimized (java) code generation for string concatenations that involve StringBuffer
 316          * creation: going through this path means that there is no need for a new StringBuffer
 317          * creation, further operands should rather be only appended to the current one.
 318          * By default: no optimization.
 319          */
 320         public void generateOptimizedStringBuffer(
 321                 BlockScope blockScope,
 322                 org.eclipse.jdt.internal.compiler.codegen.CodeStream codeStream,
 323                 int typeID) {
 324
 325                 if (typeID == T_String && this.constant != NotAConstant && this.constant.stringValue().length() == 0) {
 326                         return; // optimize str + ""
 327                 }
 328                 generateCode(blockScope, codeStream, true);
 329                 codeStream.invokeStringBufferAppendForType(typeID);
 330         }
 331
 332         /* Optimized (java) code generation for string concatenations that involve StringBuffer
 333          * creation: going through this path means that there is no need for a new StringBuffer
 334          * creation, further operands should rather be only appended to the current one.
 335          */
 336         public void generateOptimizedStringBufferCreation(
 337                 BlockScope blockScope,
 338                 CodeStream codeStream,
 339                 int typeID) {
 340
 341                 // Optimization only for integers and strings
 342                 if (typeID == T_Object) {
 343                         // in the case the runtime value of valueOf(Object) returns null, we have to use append(Object) instead of directly valueOf(Object)
 344                         // append(Object) returns append(valueOf(Object)), which means that the null case is handled by append(String).
 345                         codeStream.newStringBuffer();
 346                         codeStream.dup();
 347                         codeStream.invokeStringBufferDefaultConstructor();
 348                         generateCode(blockScope, codeStream, true);
 349                         codeStream.invokeStringBufferAppendForType(T_Object);
 350                         return;
 351                 }
 352                 codeStream.newStringBuffer();
 353                 codeStream.dup();
 354                 if (typeID == T_String || typeID == T_null) {
 355                         if (constant != NotAConstant) {
 356                                 String stringValue = constant.stringValue();
 357                                 if (stringValue.length() == 0) {  // optimize ""+<str>
 358                                         codeStream.invokeStringBufferDefaultConstructor();
 359                                         return;
 360                                 }
 361                                 codeStream.ldc(stringValue);
 362                         } else {
 363                                 generateCode(blockScope, codeStream, true);
 364                                 codeStream.invokeStringValueOf(T_Object);
 365                         }
 366                 } else {
 367                         generateCode(blockScope, codeStream, true);
 368                         codeStream.invokeStringValueOf(typeID);
 369                 }
 370                 codeStream.invokeStringBufferStringConstructor();
 371         }
 372
 373         // Base types need that the widening is explicitly done by the compiler using some bytecode like i2f
 374         public void implicitWidening(
 375                 TypeBinding runtimeTimeType,
 376                 TypeBinding compileTimeType) {
 377
 378                 if (runtimeTimeType == null || compileTimeType == null)
 379                         return;
 380
 381 //              if (compileTimeType.id == T_null) {
 382 //                      // this case is possible only for constant null
 383 //                      // The type of runtime is a reference type
 384 //                      // The code gen use the constant id thus any value
 385 //                      // for the runtime id (akak the <<4) could be used.
 386 //                      // T_Object is used as some general T_reference
 387 //                      implicitConversion = (T_Object << 4) + T_null;
 388 //                      return;
 389 //              }
 390
 391                 switch (runtimeTimeType.id) {
 392                         case T_byte :
 393                         case T_short :
 394                         case T_char :
 395                                 implicitConversion = (T_int << 4) + compileTimeType.id;
 396                                 break;
 397                         case T_String :
 398                         case T_float :
 399                         case T_boolean :
 400                         case T_double :
 401                         case T_int : //implicitConversion may result in i2i which will result in NO code gen
 402                         case T_long :
 403                                 implicitConversion = (runtimeTimeType.id << 4) + compileTimeType.id;
 404                                 break;
 405                         default : //nothing on regular object ref
 406                 }
 407         }
 408
 409         public boolean isCompactableOperation() {
 410
 411                 return false;
 412         }
 413
 414         //Return true if the conversion is done AUTOMATICALLY by the vm
 415         //while the javaVM is an int based-machine, thus for example pushing
 416         //a byte onto the stack , will automatically creates a int on the stack
 417         //(this request some work d be done by the VM on signed numbers)
 418         public boolean isConstantValueOfTypeAssignableToType(
 419                 TypeBinding constantType,
 420                 TypeBinding targetType) {
 421
 422                 if (constant == Constant.NotAConstant)
 423                         return false;
 424                 if (constantType == targetType)
 425                         return true;
 426                 if (constantType.isBaseType() && targetType.isBaseType()) {
 427                         //No free assignment conversion from anything but to integral ones.
 428                         if ((constantType == IntBinding
 429                                 || BaseTypeBinding.isWidening(T_int, constantType.id))
 430                                 && (BaseTypeBinding.isNarrowing(targetType.id, T_int))) {
 431                                 //use current explicit conversion in order to get some new value to compare with current one
 432                                 return isConstantValueRepresentable(constant, constantType.id, targetType.id);
 433                         }
 434                 }
 435                 return false;
 436         }
 437
 438         public boolean isTypeReference() {
 439                 return false;
 440         }
 441
 442         public void resolve(BlockScope scope) {
 443                 // drops the returning expression's type whatever the type is.
 444
 445                 this.resolveType(scope);
 446                 return;
 447         }
 448
 449         public TypeBinding resolveType(BlockScope scope) {
 450                 // by default... subclasses should implement a better TC if required.
 451
 452                 return null;
 453         }
 454
 455         public TypeBinding resolveType(ClassScope classScope) {
 456                 // by default... subclasses should implement a better TB if required.
 457                 return null;
 458         }
 459
 460         public TypeBinding resolveTypeExpecting(
 461                 BlockScope scope,
 462                 TypeBinding expectedType) {
 463
 464                 TypeBinding expressionType = this.resolveType(scope);
 465                 if (expressionType == null) return null;
 466                 if (expressionType == expectedType) return expressionType;
 467
 468                 if (!expressionType.isCompatibleWith(expectedType)) {
 469                         scope.problemReporter().typeMismatchError(expressionType, expectedType, this);
 470                         return null;
 471                 }
 472                 return expressionType;
 473         }
 474
 475         public StringBuffer print(int indent, StringBuffer output) {
 476                 printIndent(indent, output);
 477                 return printExpression(indent, output);
 478         }
 479
 480         public abstract StringBuffer printExpression(int indent, StringBuffer output);
 481
 482         public StringBuffer printStatement(int indent, StringBuffer output) {
 483                 return print(indent, output).append(";"); //$NON-NLS-1$
 484         }
 485
 486         public Expression toTypeReference() {
 487                 //by default undefined
 488
 489                 //this method is meanly used by the parser in order to transform
 490                 //an expression that is used as a type reference in a cast ....
 491                 //--appreciate the fact that castExpression and ExpressionWithParenthesis
 492                 //--starts with the same pattern.....
 493
 494                 return this;
 495         }
 496 }