Classify method and property accesses semantically.

pkg/analyzer2dart/lib/src/identifier_semantics.dart

+// Copyright (c) 2014, 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.
+
+/**
+ * Code for classifying the semantics of identifiers appearing in a Dart file.
+ */
+library analyzer2dart.identifierSemantics;
+
+import 'package:analyzer/analyzer.dart';
+import 'package:analyzer/src/generated/element.dart';
+
+/**
+ * Base class used to classify the semantics of a method or function
+ * invocation.
+ */
+abstract class MethodInvocationSemantics {}
+
+/**
+ * MethodInvocationSemantics object representing the invocation of a method
+ * that is defined statically within a class, or of a function that is defined
+ * at toplevel within a library.
+ */
+class StaticMethodInvocation extends MethodInvocationSemantics {
+  /**
+   * The method or function being invoked.
+   */
+  final ExecutableElement methodElement;
+
+  /**
+   * The class containing the member being invoked, or null if a toplevel
+   * function is being invoked.
+   */
+  final ClassElement classElement;
+
+  /**
+   * The identifier being used to invoke the method or function.
+   */
+  final SimpleIdentifier methodName;
+
+  // TODO(paulberry): would it also be useful to store the libraryElement?
+
+  StaticMethodInvocation(this.methodElement, this.classElement,
+      this.methodName);
+}
+
+/**
+ * MethodInvocationSemantics object representing the invocation of a function
+ * that is defined inside of another function or method.
+ */
+class LocalFunctionInvocation extends MethodInvocationSemantics {
+  /**
+   * The function being invoked.
+   */
+  final FunctionElement functionElement;
+
+  LocalFunctionInvocation(this.functionElement);
+}
+
+/**
+ * MethodInvocationSemantics object representing the invocation of an instance
+ * method within a class.
+ *
+ * This also handles calls to an undefined method using a bare
+ * identifier (since it cannot be determined until runtime whether the method
+ * is truly undefined).
+ */
+class DynamicMethodInvocation extends MethodInvocationSemantics {
+  /**
+   * The expression on which the method is being invoked (or null if the target
+   * is an implicit "this").
+   */
+  final Expression target;
+
+  /**
+   * The identifier being used to invoke the method.
+   */
+  final SimpleIdentifier methodName;
+
+  DynamicMethodInvocation(this.target, this.methodName);
+}
+
+/**
+ * Base class used to classify the semantics of a property access.
+ */
+abstract class AccessSemantics {
+  /**
+   * The identifier being used to access the property.
+   */
+  final SimpleIdentifier _identifier;
+
+  AccessSemantics(this._identifier);
+
+  /**
+   * True if this is a read access to the property.  Note that both
+   * [isRead] and [isWrite] will be true in the case of a read-modify-write
+   * operation (e.g. "+=").
+   */
+  bool get isRead => _identifier.inGetterContext();
+
+  /**
+   * True if this is a write access to the property.  Note that both
+   * [isRead] and [isWrite] will be true in the case of a read-modify-write
+   * operation (e.g. "+=").
+   */
+  bool get isWrite => _identifier.inSetterContext();
+}
+
+/**
+ * AccessSemantics object representing an access to a field that is defined
+ * statically within a class, or to a variable that is defined at toplevel
+ * within a library.
+ */
+class StaticFieldAccess extends AccessSemantics {
+  /**
+   * The field or variable being referenced.
+   */
+  final PropertyInducingElement field;
+
+  /**
+   * The class containing the field being referenced, or null if a toplevel
+   * variable is being referenced.
+   */
+  final ClassElement classElement;
+
+  // TODO(paulberry): would it also be useful to store the libraryElement?
+
+  StaticFieldAccess(this.field, this.classElement, SimpleIdentifier identifier)
+      : super(identifier);
+}
+
+/**
+ * AccessSemantics object representing an access to a property that is defined
+ * statically within a class, or defined at toplevel within a library.
+ */
+class StaticPropertyAccess extends AccessSemantics {
+  /**
+   * The property being referenced, or null if the property is undefined.
+   */
+  final PropertyAccessorElement property;
+
+  /**
+   * The class containing the property being referenced, or null if a toplevel
+   * property is being referenced.
+   */
+  final ClassElement classElement;
+
+  /**
+   * The identifier being used to access the property.
+   */
+  SimpleIdentifier get propertyName => _identifier;
+
+  // TODO(paulberry): would it also be useful to store the libraryElement?
+
+  StaticPropertyAccess(this.property, this.classElement,
+      SimpleIdentifier propertyName)
+      : super(propertyName);
+}
+
+/**
+ * AccessSemantics object representing an access to an instance property or
+ * field within a class.
+ *
+ * This also handles access to an undefined property using a bare
+ * identifier (since it cannot be determined until runtime whether the property
+ * is truly undefined).
+ */
+class DynamicPropertyAccess extends AccessSemantics {
+  /**
+   * The expression on which the method is being invoked (or null if the target
+   * is an implicit "this").
+   */
+  final Expression target;
+
+  /**
+   * The identifier being used to access the property.
+   */
+  final SimpleIdentifier propertyName;
+
+  DynamicPropertyAccess(this.target, SimpleIdentifier propertyName)
+      : super(propertyName),
+        propertyName = propertyName;
+}
+
+/**
+ * AccessSemantics object representing an access to a local variable within a
+ * function or method.
+ */
+class LocalVariableAccess extends AccessSemantics {
+  final LocalVariableElement variable;
+  LocalVariableAccess(this.variable, SimpleIdentifier identifier)
+      : super(identifier);
+}
+
+/**
+ * Return the method invocation semantics for [node].
+ */
+MethodInvocationSemantics classifyMethodInvocation(MethodInvocation node) {
+  Expression target = node.realTarget;
+  if (target == null) {
+    Element staticElement = node.methodName.staticElement;
+    if (staticElement is FunctionElement) {
+      if (staticElement.enclosingElement is CompilationUnitElement) {
+        return new StaticMethodInvocation(staticElement, null, node.methodName);
+      } else {
+        return new LocalFunctionInvocation(staticElement);
+      }
+    } else if (staticElement is MethodElement && staticElement.isStatic) {
+      return new StaticMethodInvocation(
+          staticElement,
+          staticElement.enclosingElement,
+          node.methodName);
+    }

[Brian Wilkerson, 2014/09/22 19:44:48]

It's also possible for the static element to be a PropertyAccessorElement:

typedef int F(int x);

class C {
  F f;
  int three() {
    return f(3);
  }
}

[Paul Berry, 2014/09/23 16:32:49]

Done.

+  } else if (target is SimpleIdentifier) {
+    Element targetStaticElement = target.staticElement;
+    if (targetStaticElement is PrefixElement) {
+      if (node.methodName.staticElement != null) {
+        return new StaticMethodInvocation(
+            node.methodName.staticElement,
+            null,
+            node.methodName);
+      } else {
+        return new DynamicMethodInvocation(null, node.methodName);
+      }
+    } else if (targetStaticElement is ClassElement) {
+      return new StaticMethodInvocation(
+          node.methodName.staticElement,
+          targetStaticElement,
+          node.methodName);
+    }
+  }

[Brian Wilkerson, 2014/09/22 19:44:47]

This is missing the case where the target is a PrefixedIdentifier representing a
class:

import 'lib.dart' as 'p';

f() {
  p.SomeClass.staticMethod();
}

[Paul Berry, 2014/09/23 16:32:49]

Done.  It turned out that I was able to handle this by simply changing "if
(target is SimpleIdentifier)" to "if (target is Identifier)".

+  return new DynamicMethodInvocation(target, node.methodName);
+}
+
+/**
+ * Return the access semantics for [node].
+ */
+AccessSemantics classifyPrefixedIdentifier(PrefixedIdentifier node) {
+  Element prefixElement = node.prefix.staticElement;
+  Element suffixElement = node.identifier.staticElement;
+  if (prefixElement is PrefixElement) {
+    Element staticElement = node.identifier.staticElement;

[Brian Wilkerson, 2014/09/22 19:44:48]

staticElement == suffixElement

[Paul Berry, 2014/09/23 16:32:49]

Done.

+    if (staticElement is PropertyAccessorElement) {
+      if (staticElement.isSynthetic) {
+        return new StaticFieldAccess(
+            staticElement.variable,
+            null,
+            node.identifier);
+      } else {
+        return new StaticPropertyAccess(staticElement, null, node.identifier);
+      }
+    }
+    return new DynamicPropertyAccess(null, node.identifier);
+  } else if (prefixElement is ClassElement) {
+    if (suffixElement is PropertyAccessorElement && suffixElement.isSynthetic) {
+      return new StaticFieldAccess(
+          suffixElement.variable,
+          prefixElement,
+          node.identifier);
+    }
+    return new StaticPropertyAccess(
+        suffixElement,
+        prefixElement,
+        node.identifier);
+  } else {
+    return new DynamicPropertyAccess(node.prefix, node.identifier);

[Brian Wilkerson, 2014/09/22 19:44:47]

Do we represent method tear-offs as property accesses?

[Paul Berry, 2014/09/23 16:32:49]

Method tear-offs weren't being handled properly.  They are now represented as an
AccessSemantics object whose kind is STATIC_METHOD, LOCAL_FUNCTION, or DYNAMIC,
and whose isInvoke boolean is true.

+  }
+}
+
+/**
+ * Return the access semantics for [node].
+ */
+DynamicPropertyAccess classifyPropertyAccess(PropertyAccess node) {
+  return new DynamicPropertyAccess(node.realTarget, node.propertyName);
+}
+
+/**
+ * Return the access semantics for [node].  Caller must ensure that [node] is
+ * not the right hand side of a [PropertyAccess] or [PrefixedIdentifier], or
+ * the method name of a [MethodInvocation].
+ */
+AccessSemantics classifyBareIdentifier(SimpleIdentifier node) {
+  AstNode parent = node.parent;
+  if ((parent is FunctionDeclaration && parent.name == node) ||

[Brian Wilkerson, 2014/09/22 19:44:47]

Replace this 'if' with

if (node.inDeclarationContext()) {
  return null;
}

[Paul Berry, 2014/09/23 16:32:49]

Aha, that's much better.  Thanks!

+      parent is ImportDirective ||
+      (parent is ClassDeclaration && parent.name == node) ||
+      (parent is MethodDeclaration && parent.name == node) ||
+      (parent is VariableDeclaration && parent.name == node) ||
+      (parent is FormalParameter && parent.identifier == node)) {
+    // This identifier is a declaration, not a use.
+    // TODO(paulberry): Can some of the above cases be coalesced?
+    // TODO(paulberry): Additional cases
+    return null;
+  }
+  if (parent is TypeName) {
+    // TODO(paulberry): handle this case.

[Brian Wilkerson, 2014/09/22 19:44:48]

It might be cleanest to not visit the children of a TypeName when visiting the
AST structure.

[Paul Berry, 2014/09/23 16:32:49]

Hmm, that may be true.  I'm not sure whether I want to saddle clients of this
code with that responsibility, though.  For now, I've expanded the TODO comment
to include this as on option.

[Brian Wilkerson, 2014/09/23 17:03:58]

It looks like you're currently exiting if you're visiting the child of a type
name, so it isn't clear what new responsibilities clients would be have to
perform that they don't have to perform today, but I could easily be missing
something.

[Paul Berry, 2014/09/23 17:45:56]

Acknowledged.

+    return null;
+  }
+  // TODO(paulberry): handle PrefixElement.
+  Element staticElement = node.staticElement;
+  if (staticElement is PropertyAccessorElement) {
+    if (staticElement.isSynthetic) {
+      if (staticElement.enclosingElement is CompilationUnitElement) {
+        return new StaticFieldAccess(staticElement.variable, null, node);
+      } else if (staticElement.isStatic) {
+        return new StaticFieldAccess(
+            staticElement.variable,
+            staticElement.enclosingElement,
+            node);
+      }
+    } else {
+      if (staticElement.enclosingElement is CompilationUnitElement) {
+        return new StaticPropertyAccess(staticElement, null, node);
+      } else if (staticElement.isStatic) {
+        return new StaticPropertyAccess(
+            staticElement,
+            staticElement.enclosingElement,
+            node);
+      }
+    }
+  } else if (staticElement is LocalVariableElement) {
+    return new LocalVariableAccess(staticElement, node);
+  }

[Brian Wilkerson, 2014/09/22 19:44:48]

Missing ParameterElement?

[Paul Berry, 2014/09/23 16:32:49]

Done.

+  return new DynamicPropertyAccess(null, node);
+}