Compile Time Constants cycle check

compiler/java/com/google/dart/compiler/resolver/CompileTimeConstantAnalyzer.java

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.google.dart.compiler.resolver;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
+import com.google.dart.compiler.DartCompilationError;
+import com.google.dart.compiler.DartCompilationPhase;
+import com.google.dart.compiler.DartCompilerContext;
+import com.google.dart.compiler.InternalCompilerException;
+import com.google.dart.compiler.ast.DartArrayLiteral;
+import com.google.dart.compiler.ast.DartBinaryExpression;
+import com.google.dart.compiler.ast.DartBooleanLiteral;
+import com.google.dart.compiler.ast.DartDoubleLiteral;
+import com.google.dart.compiler.ast.DartExpression;
+import com.google.dart.compiler.ast.DartField;
+import com.google.dart.compiler.ast.DartFunction;
+import com.google.dart.compiler.ast.DartFunctionObjectInvocation;
+import com.google.dart.compiler.ast.DartIdentifier;
+import com.google.dart.compiler.ast.DartIntegerLiteral;
+import com.google.dart.compiler.ast.DartInvocation;
+import com.google.dart.compiler.ast.DartMapLiteral;
+import com.google.dart.compiler.ast.DartMapLiteralEntry;
+import com.google.dart.compiler.ast.DartMethodDefinition;
+import com.google.dart.compiler.ast.DartMethodInvocation;
+import com.google.dart.compiler.ast.DartNewExpression;
+import com.google.dart.compiler.ast.DartNode;
+import com.google.dart.compiler.ast.DartNodeTraverser;
+import com.google.dart.compiler.ast.DartParameter;
+import com.google.dart.compiler.ast.DartParenthesizedExpression;
+import com.google.dart.compiler.ast.DartPropertyAccess;
+import com.google.dart.compiler.ast.DartRedirectConstructorInvocation;
+import com.google.dart.compiler.ast.DartStringInterpolation;
+import com.google.dart.compiler.ast.DartStringLiteral;
+import com.google.dart.compiler.ast.DartSuperExpression;
+import com.google.dart.compiler.ast.DartThisExpression;
+import com.google.dart.compiler.ast.DartUnaryExpression;
+import com.google.dart.compiler.ast.DartUnit;
+import com.google.dart.compiler.ast.DartUnqualifiedInvocation;
+import com.google.dart.compiler.ast.DartVariable;
+import com.google.dart.compiler.ast.DartVariableStatement;
+import com.google.dart.compiler.ast.Modifiers;
+import com.google.dart.compiler.common.Symbol;
+import com.google.dart.compiler.type.Type;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Given an expression, Determines if the expression matches all the rules for a
+ * compile-time constant expression and emits a resolution error if not.
+ *
+ * This script doesn't just resolve expressions, it also sets types to the
+ * extent needed to validate compile-time constant expressions (boolean, int,
+ * double, and string types might be set)
+ *
+ */
+public class CompileTimeConstantAnalyzer extends DartNodeTraverser<Void> {
+
+  public static class Phase implements DartCompilationPhase {
+    /**
+     * Executes symbol resolution on the given compilation unit.
+     *
+     * @param context The listener through which compilation errors are reported
+     *          (not <code>null</code>)
+     */
+    @Override
+    public DartUnit exec(DartUnit unit, DartCompilerContext context,
+                         CoreTypeProvider typeProvider) {
+      new CompileTimeConstantAnalyzer(typeProvider, context).exec(unit);
+      return unit;
+    }
+  }
+  private class ExpressionVisitor extends DartNodeTraverser<Void> {
+    private ExpressionVisitor() {
+    }
+
+    private boolean checkBoolean(DartNode x, Type type) {
+      if (!type.equals(boolType)) {
+        context.onError(new DartCompilationError(x,
+            ResolverErrorCode.EXPECTED_CONSTANT_EXPRESSION_BOOLEAN, type
+                .toString()));
+        return false;
+      }
+      return true;
+    }
+
+    private boolean checkInt(DartNode x, Type type) {
+      if (!type.equals(intType)) {
+        context
+            .onError(new DartCompilationError(x,
+                ResolverErrorCode.EXPECTED_CONSTANT_EXPRESSION_INT, type
+                    .toString()));
+        return false;
+      }
+      return true;
+    }
+
+    private boolean checkNumber(DartNode x, Type type) {
+      if (!(type.equals(numType) || type.equals(intType) || type
+          .equals(doubleType))) {
+        context.onError(new DartCompilationError(x,
+            ResolverErrorCode.EXPECTED_CONSTANT_EXPRESSION_NUMBER, type
+                .toString()));
+
+        return false;
+      }
+      return true;
+    }
+
+    private boolean checkNumberBooleanOrStringType(DartNode x, Type type) {
+      if (!type.equals(intType) && !type.equals(boolType)
+          && !type.equals(numType) && !type.equals(doubleType)
+          && !type.equals(stringType)) {
+        context.onError(new DartCompilationError(x,
+            ResolverErrorCode.EXPECTED_CONSTANT_EXPRESSION_STRING_NUMBER_BOOL,
+            type.toString()));
+        return false;
+      }
+      return true;
+    }
+
+    /**
+     * Logs a general message "expected a constant expression" error. Use a more
+     * specific error message when possible.
+     */
+    private void expectedConstant(DartNode x) {
+      context.onError(new DartCompilationError(x,
+          ResolverErrorCode.EXPECTED_CONSTANT_EXPRESSION));
+    }
+
+    /**
+     * Determine the most specific type assigned to an expression node. Prefer
+     * the setting in the expression's symbol if present. Otherwise, use a type
+     * tagged in the expression node itself.
+     *
+     * @return a non <code>null</code> type value. Dynamic if none other can be
+     * determined.
+     */
+    private Type getMostSpecificType(DartNode node) {
+      Element element = (Element) node.getSymbol();
+      Type type = inferredTypes.get(node);

[zundel, 2011/11/16 19:25:01]

First, consult the local hash table.

+      if (type != null) {
+        return type;
+      }
+
+      switch (ElementKind.of(element)) {
+        case FIELD:
+          type = ((FieldElement) element).getType();
+          break;
+        case METHOD:
+          type = ((MethodElement) element).getType();
+          break;
+        case VARIABLE:
+          type = ((VariableElement) element).getType();
+          break;
+        case CONSTRUCTOR:
+          type = ((ConstructorElement) element).getType();
+          break;
+        case NONE:
+          if (node.getType() != null) {
+            return node.getType();
+          }
+          return dynamicType;
+        default:
+          throw new InternalCompilerException("Unexpected element "
+              + node.toString() + " kind: " + ElementKind.of(element)
+              + "evaluating type for compile-time constant expression.");
+      }
+      if (type == null) {
+        return node.getType();
+      }
+      return type;
+    }
+
+    private void setType(DartNode x, Type type) {

[zundel, 2011/11/16 19:25:01]

This method used to set the type on the node, but now it only sets it in a local
hash table to avoid interfering with the Dart type analyzer.

+      if (type != null && ! type.equals(dynamicType)) {
+        inferredTypes.put(x,  type);
+      }
+    }
+
+    @Override
+    public Void visitArrayLiteral(DartArrayLiteral x) {
+      if (!x.isConst()) {
+        expectedConstant(x);
+      } else {
+        for (DartExpression expr : x.getExpressions()) {
+          expr.accept(this);
+        }
+      }
+      return null;
+    }
+
+    @Override
+    public Void visitBinaryExpression(DartBinaryExpression x) {
+      x.visitChildren(this);
+
+      DartExpression lhs = x.getArg1();
+      DartExpression rhs = x.getArg2();
+      Type lhsType = getMostSpecificType(lhs);
+      Type rhsType = getMostSpecificType(rhs);
+      if (lhsType == null) {
+        lhsType = dynamicType;
+      }
+      if (rhsType == null) {
+        rhsType = dynamicType;
+      }
+
+      switch (x.getOperator()) {
+        case NE:
+        case EQ:
+        case NE_STRICT:
+        case EQ_STRICT:
+          if (checkNumberBooleanOrStringType(lhs, lhsType)
+              && checkNumberBooleanOrStringType(rhs, rhsType)) {
+            setType(x, boolType);
+          }
+          break;
+
+        case AND:
+        case OR:
+          if (checkBoolean(lhs, lhsType) && checkBoolean(rhs, rhsType)) {
+            setType(x, boolType);
+          }
+          break;
+
+        case BIT_NOT:
+        case TRUNC:
+        case BIT_XOR:
+        case BIT_AND:
+        case BIT_OR:
+        case SAR:
+        case SHL:
+          if (checkInt(lhs, lhsType) && checkInt(rhs, rhsType)) {
+            setType(x, intType);
+          }
+          break;
+
+        case ADD:
+        case SUB:
+        case MUL:
+        case DIV:
+        case MOD:
+          if (checkNumber(lhs, lhsType) && checkNumber(rhs, rhsType)) {
+            setType(x, numType);
+          }
+          break;
+        case LT:
+        case GT:
+        case LTE:
+        case GTE:
+          if (checkNumber(lhs, lhsType) && checkNumber(rhs, rhsType)) {
+            setType(x, boolType);
+          }
+          break;
+
+        default:
+          // all other operators...
+          expectedConstant(x);
+      }
+      return null;
+    }
+
+    @Override
+    public Void visitBooleanLiteral(DartBooleanLiteral x) {
+      setType(x, boolType);
+      return null;
+    }
+
+    @Override
+    public Void visitDoubleLiteral(DartDoubleLiteral x) {
+      setType(x, doubleType);
+      return null;
+    }
+
+    @Override
+    public Void visitField(DartField x) {
+      x.visitChildren(this);
+      if (x.getType() == null || x.getType().equals(dynamicType)) {
+        Type type = getMostSpecificType(x.getValue());
+        setType(x, type);
+      }
+      return null;
+    }
+
+    @Override
+    public Void visitFunction(DartFunction x) {
+      // No need to traverse, functions are always disallowed.
+      expectedConstant(x);
+      return null;
+    }
+
+    @Override
+    public Void visitFunctionObjectInvocation(DartFunctionObjectInvocation x) {
+      // No need to traverse, function object invocations are always disallowed.
+      expectedConstant(x);
+      return null;
+    }
+
+    @Override
+    public Void visitIdentifier(DartIdentifier x) {
+      x.visitChildren(this);
+
+      Element element = x.getSymbol();
+      switch (ElementKind.of(element)) {
+        case CLASS:
+        case PARAMETER:
+          // OK
+          break;
+        case FIELD:
+        case VARIABLE:
+
+          if (element != null && visitedSymbols.contains(element)) {
+            context.onError(new DartCompilationError(x,
+                ResolverErrorCode.CIRCULAR_REFERENCE));
+            setType(x, getMostSpecificType(x));
+            return null;
+          }
+          visitedSymbols.add(element);
+
+          if (!element.getModifiers().isConstant()) {
+            expectedConstant(x);
+          }
+          DartNode identifierNode = element.getNode();
+
+          switch (ElementKind.of(element)) {
+            case FIELD:
+              setType(x, getMostSpecificType(x));
+              break;
+          }
+          this.visit(Lists.newArrayList(identifierNode));
+
+          visitedSymbols.remove(element);
+
+          switch (ElementKind.of(element)) {
+            case FIELD:
+              setType(x, getMostSpecificType(identifierNode));
+              break;
+          }
+
+          break;
+
+        case CONSTRUCTOR:
+          if (!element.getModifiers().isConstant()) {
+            expectedConstant(x);
+          }
+          setType(x, getMostSpecificType(x));
+          break;
+
+        case NONE:
+          Type type = getMostSpecificType(x);
+          if (dynamicType.equals(type)) {
+            // TODO(zundel) This is the case for unresolved identifiers that
+            // need to be recursively
+            // checked.
+            expectedConstant(x);
+          }
+          setType(x, type);
+          break;
+        default:
+          throw new InternalCompilerException("Unexpected element "
+              + x.toString() + " kind: " + ElementKind.of(element)
+              + " evaluating type for compile-time constant expression.");
+      }
+      return null;
+    }
+
+
+    @Override
+    public Void visitIntegerLiteral(DartIntegerLiteral x) {
+      setType(x, intType);
+      return null;
+    }
+
+    @Override
+    public Void visitInvocation(DartInvocation x) {
+      // No need to traverse, invocations are always disallowed.
+      expectedConstant(x);
+      return null;
+    }
+
+    @Override
+    public Void visitMapLiteral(DartMapLiteral x) {
+      if (!x.isConst()) {
+        expectedConstant(x);
+      } else {
+        for (DartMapLiteralEntry entry : x.getEntries()) {
+          entry.accept(this);
+        }
+      }
+      return null;
+    }
+
+    @Override
+    public Void visitMethodInvocation(DartMethodInvocation x) {
+      // No need to traverse, method invocations are always disallowed.
+      expectedConstant(x);
+      return null;
+    }
+
+    @Override
+    public Void visitNewExpression(DartNewExpression x) {
+      if (!x.isConst()) {
+        expectedConstant(x);
+      } else {
+        for (DartExpression arg : x.getArgs()) {
+          arg.accept(this);
+        }
+      }
+      setType(x, x.getConstructor().getType());
+      return null;
+    }
+
+    @Override
+    public Void visitParenthesizedExpression(DartParenthesizedExpression x) {
+      x.visitChildren(this);
+      Type type = getMostSpecificType(x.getExpression());
+      setType(x, type);
+      return null;
+    }
+
+    @Override
+    public Void visitPropertyAccess(DartPropertyAccess x) {
+      x.visitChildren(this);
+      switch (ElementKind.of(x.getQualifier().getSymbol())) {
+        case CLASS:
+        case LIBRARY:
+        case NONE:
+          // OK.
+          break;
+        default:
+          expectedConstant(x);
+          return null;
+      }
+      Element element = x.getName().getSymbol();
+      if (element != null && !element.getModifiers().isConstant()) {
+        expectedConstant(x);
+      }
+      Type type = getMostSpecificType(x.getName());
+      setType(x, type);
+      return null;
+    }
+
+    @Override
+    public Void visitRedirectConstructorInvocation(DartRedirectConstructorInvocation x) {
+      Element element = x.getSymbol();
+      if (element != null) {
+        if (!element.getModifiers().isConstant()) {
+          expectedConstant(x);
+        }
+      }
+      x.visitChildren(this);
+      return null;
+    }
+
+    @Override
+    public Void visitStringInterpolation(DartStringInterpolation x) {
+      expectedConstant(x);
+      return null;
+    }
+
+    @Override
+    public Void visitStringLiteral(DartStringLiteral x) {
+      setType(x, stringType);
+      return null;
+    }
+
+    @Override
+    public Void visitSuperExpression(DartSuperExpression x) {
+      // No need to traverse further - super() expressions are never constant
+      expectedConstant(x);
+      return null;
+    }
+
+    @Override
+    public Void visitThisExpression(DartThisExpression x) {
+      // No need to traverse, this expressions are always disallowed.
+      expectedConstant(x);
+      return null;
+    }
+
+    @Override
+    public Void visitUnaryExpression(DartUnaryExpression x) {
+      x.visitChildren(this);
+
+      Type type = getMostSpecificType(x.getArg());
+      switch (x.getOperator()) {
+        case NOT:
+          if (checkBoolean(x, type)) {
+            setType(x, boolType);
+          }
+          break;
+        case SUB:
+          if (checkNumber(x, type)) {
+            setType(x, numType);
+          }
+          break;
+        case BIT_NOT:
+          if (checkInt(x, type)) {
+            setType(x, intType);
+          }
+          break;
+        default:
+          expectedConstant(x);
+      }
+      return null;
+    }
+
+    @Override
+    public Void visitUnqualifiedInvocation(DartUnqualifiedInvocation x) {
+      // No need to traverse, always disallowed.
+      expectedConstant(x);
+      return null;
+    }
+  }
+
+  public void exec (DartUnit unit) {
+    unit.accept(this);
+  }
+
+  public Set<Symbol> visitedSymbols = Sets.newHashSet();
+
+  public Map<DartNode, Type> inferredTypes = Maps.newHashMap();
+
+  private final DartCompilerContext context;
+  private final Type boolType;
+  private final Type doubleType;
+  private final Type intType;
+  private final Type numType;
+  private final Type stringType;
+  private final Type dynamicType;
+
+  public CompileTimeConstantAnalyzer(CoreTypeProvider typeProvider,
+      DartCompilerContext context) {
+    this.context = context;
+    this.boolType = typeProvider.getBoolType();
+    this.doubleType = typeProvider.getDoubleType();
+    this.intType = typeProvider.getIntType();
+    this.numType = typeProvider.getNumType();
+    this.stringType = typeProvider.getStringType();
+    this.dynamicType = typeProvider.getDynamicType();
+  }
+
+  private void checkConstantExpression(DartExpression expression) {
+    if (expression != null) {
+      expression.accept(new ExpressionVisitor());
+    }
+  }
+
+  @Override
+  public Void visitField(DartField node) {
+    checkConstantExpression(node.getValue());
+    return null;
+  }
+
+  @Override
+  public Void visitMethodDefinition(DartMethodDefinition node) {
+    DartFunction functionNode = node.getFunction();
+    List<DartParameter> parameters = functionNode.getParams();
+    for (DartParameter parameter : parameters) {
+      // Then resolve the default values.
+      checkConstantExpression(parameter.getDefaultExpr());
+    }
+    return null;
+  }
+
+  @Override
+  public Void visitNewExpression(DartNewExpression node) {
+    if (node.isConst()) {
+      for (DartExpression arg : node.getArgs()) {
+       checkConstantExpression(arg);
+      }
+    }
+    return null;
+  }
+
+  @Override
+  public Void visitParameter(DartParameter node) {
+    checkConstantExpression(node.getDefaultExpr());
+    return null;
+  }
+
+  @Override
+  public Void visitVariableStatement(DartVariableStatement node) {
+    for (DartVariable variable : node.getVariables()) {
+      Modifiers modifiers = node.getModifiers();
+      if (modifiers.isStatic() && modifiers.isFinal() && variable.getValue() != null) {
+        checkConstantExpression(variable.getValue());
+      }
+    }
+    return null;
+  }
+}