Pulling the element model out of global type inference.

pkg/compiler/lib/src/inferrer/builder_kernel.dart

+// Copyright (c) 2017, 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.
+
+import 'package:kernel/ast.dart' as ir;
+
+import '../closure.dart';
+import '../compiler.dart';
+import '../elements/elements.dart';
+import '../elements/entities.dart';
+import '../kernel/kernel.dart';
+import '../ssa/kernel_ast_adapter.dart';
+import '../tree/tree.dart' as ast;
+import '../types/types.dart' show TypeMask;
+import '../universe/side_effects.dart' show SideEffects;
+import 'inferrer_engine.dart';
+import 'locals_handler.dart';
+import 'type_graph_nodes.dart';
+import 'type_system.dart';
+
+/// [KernelTypeGraphBuilder] can be thought of as a type-inference graph

[Siggi Cherem (dart-lang), 2017/03/16 00:37:44]

BTW - we should be able to update these comments a bit. They were written when
the name of this class was "SimpleTypeInferrerVisitor" so we had to explain it
was sort of like a builder :)

[Emily Fortuna, 2017/03/17 01:03:02]

Done.

+/// builder for a single element.
+///
+/// Calling [run] will start the work of visiting the body of the code to
+/// construct a set of infernece-nodes that abstractly represent what the code
+/// is doing.
+///
+/// This visitor is parameterized by an [InferenceEngine], which internally

[Siggi Cherem (dart-lang), 2017/03/16 00:37:44]

similarly note the engine parameter is now gone (Johnni got rid of it, we seem
to still have the old comments though)

[Emily Fortuna, 2017/03/17 01:03:01]

Done.

+/// decides how to represent inference nodes.
+class KernelTypeGraphBuilder extends ir.Visitor<TypeInformation> {
+  final Compiler compiler;
+  final AstElement originalElement;
+  // TODO(efortuna): Remove this.
+  final Element outermostElement;
+  ir.Node analyzedNode;
+  final ResolvedAst resolvedAst;
+  final TypeSystem types;
+  LocalsHandler locals;
+  final InferrerEngine inferrer;
+  SideEffects sideEffects = new SideEffects.empty();
+  int loopLevel = 0;
+  final Set<Entity> capturedVariables = new Set<Entity>();
+
+  KernelAstAdapter astAdapter;
+
+  bool get inLoop => loopLevel > 0;

[Siggi Cherem (dart-lang), 2017/03/16 00:37:44]

nit: I'd move htis up next to loopLevel (it mixes fields and getters, but I
think there are so coupled that it's nice to see them together.

[Emily Fortuna, 2017/03/17 01:03:02]

Done.

+
+  KernelTypeGraphBuilder.internal(this.originalElement, this.resolvedAst,
+      this.outermostElement, this.inferrer, this.compiler, this.locals)
+      : this.types = inferrer.types {
+    if (locals != null) return;
+
+    Kernel kernel = compiler.backend.kernelTask.kernel;
+    this.astAdapter = new KernelAstAdapter(kernel, compiler.backend,

[Siggi Cherem (dart-lang), 2017/03/16 00:37:45]

it might not be worth making this change because the adapter is temporary, but
if it were more permanent I'd try to make this an initializer so we could make
the field final. It should be possible either with a helper function or with a
factory method. For example:

  : astAdapter = _createKernelAdapter(compiler, resolvedAst);

[Emily Fortuna, 2017/03/17 01:03:02]

Done.

+        resolvedAst, kernel.nodeToAst, kernel.nodeToElement);
+
+    analyzedNode = astAdapter.getInitialKernelNode(originalElement);

[Siggi Cherem (dart-lang), 2017/03/16 00:37:44]

will analyzerNode ever change? If not, then maybe going the factory route might
be easier to make it final as well.

[Emily Fortuna, 2017/03/17 01:03:02]

Done.

+
+    ast.Node node;

[Siggi Cherem (dart-lang), 2017/03/16 00:37:45]

I'm guessing the idea is this will be replaced by the analyzedNode once we get
to change the locals handler?

[Emily Fortuna, 2017/03/17 01:03:01]

yep. The list of things to do grows very quickly!

+    if (resolvedAst.kind == ResolvedAstKind.PARSED) {
+      node = resolvedAst.node;
+    }
+    FieldInitializationScope fieldScope = (analyzedNode is ir.Constructor)
+        ? new FieldInitializationScope(types)
+        : null;
+    locals =
+        new LocalsHandler(inferrer, types, compiler.options, node, fieldScope);
+  }
+
+  KernelTypeGraphBuilder(Element element, ResolvedAst resolvedAst,
+      Compiler compiler, InferrerEngine inferrer, [LocalsHandler handler])
+      : this.internal(
+            element,
+            resolvedAst,
+            element.outermostEnclosingMemberOrTopLevel.implementation,
+            inferrer,
+            compiler,
+            handler);
+
+  TypeInformation run() {
+    ir.Expression initializer;
+    if (analyzedNode is ir.Field) {
+      initializer = (analyzedNode as ir.Field).initializer;

[Siggi Cherem (dart-lang), 2017/03/16 00:37:45]

If we can make analyzerNode final above, then this cast will no longer be
necessary (the is-check will promote the field).

Meanwhile, a convention we follow in dart2js is to avoid the cast and instead do
an assignment to a temporary variable with the precise type:

if (analyzedNode is ir.Field) {
  ir.Field field = analyzerdNode;
  if (field.initializer == null) ...

This makes it a cast in checked-mode, but free in production mode. In the future
with strong-mode, there wont be that difference anymore though.

[Emily Fortuna, 2017/03/17 01:03:02]

Hmm I made this change complete with the finals, and the analyze_unused_test was
still unhappy about it.  I went with the renaming/typing the variable instead.

[Siggi Cherem (dart-lang), 2017/03/17 21:10:17]

interesting - I think I understand why now - this class could have a subclass
that overrides the field with a getter/setter pair and makes it non-final.... :(

+      if (initializer == null) {
+        // Eagerly bailout, because computing the closure data only
+        // works for functions and field assignments.
+        return types.nullType;
+      }
+    }
+
+    // Update the locals that are boxed in [locals]. These locals will
+    // be handled specially, in that we are computing their LUB at
+    // each update, and reading them yields the type that was found in a
+    // previous analysis of [outermostElement].
+    ClosureClassMap closureData =
+        compiler.closureToClassMapper.getClosureToClassMapping(resolvedAst);
+    closureData.forEachCapturedVariable((variable, field) {
+      locals.setCaptured(variable, field);
+    });
+    closureData.forEachBoxedVariable((variable, field) {
+      locals.setCapturedAndBoxed(variable, field);
+    });
+
+    if (analyzedNode is ir.Field) {
+      return initializer.accept(this);
+    }
+    return _processFunctionNode(analyzedNode);
+  }
+
+  TypeInformation _processFunctionNode(ir.FunctionNode funcNode) {
+    // TODO(efortuna): Implement.
+    return types.dynamicType;
+  }
+
+  @override
+  TypeInformation defaultExpression(ir.Expression expression) {
+    // TODO(efortuna): Remove when more is implemented.
+    return types.dynamicType;
+  }
+
+  @override
+  TypeInformation visitNullLiteral(ir.NullLiteral literal) {
+    return types.nullType;
+  }
+
+  @override
+  TypeInformation visitBlock(ir.Block block) {
+    for (ir.Statement statement in block.statements) {
+      statement.accept(this);
+      if (locals.aborts) break;
+    }
+    return null;
+  }
+
+  @override
+  TypeInformation visitListLiteral(ir.ListLiteral listLiteral) {
+    // We only set the type once. We don't need to re-visit the children
+    // when re-analyzing the node.
+    return inferrer.concreteKernelTypes.putIfAbsent(listLiteral, () {
+      TypeInformation elementType;
+      int length = 0;
+      for (ir.Expression element in listLiteral.expressions) {
+        TypeInformation type = element.accept(this);
+        elementType = elementType == null
+            ? types.allocatePhi(null, null, type)
+            : types.addPhiInput(null, elementType, type);
+        length++;
+      }
+      elementType = elementType == null
+          ? types.nonNullEmpty()
+          : types.simplifyPhi(null, null, elementType);
+      TypeInformation containerType =
+          listLiteral.isConst ? types.constListType : types.growableListType;
+      // TODO(efortuna): Change signature of allocateList and the rest of
+      // type_system to deal with Kernel elements.
+      return types.allocateList(containerType, astAdapter.getNode(listLiteral),
+          outermostElement, elementType, length);
+    });
+  }
+}