Implements simple statement executer

Implements simple statement executer

This change adds support for executing:
 - BlockStatement
 - ExpressionStatement
 - IfStatement
 - VariableDeclaration

Currently only BlockStatement introduces a new environment and
VariableDeclaration modifies the environment.

BUG=
R=kmillikin@google.com

Committed: https://github.com/dart-lang/sdk/commit/23cc114c2f61596f5b168cd3b08107c03851bbbe

[zhivkag, 2017-03-27 13:14:57]

zhivkag@google.com changed reviewers:
+ kmillikin@google.com

[Kevin Millikin (Google), 2017-03-28 07:11:21]

LGTM with some suggestions.

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
File pkg/kernel/lib/interpreter/interpreter.dart (right):

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
pkg/kernel/lib/interpreter/interpreter.dart:232: defaultStatement(Statement
node, env) {}
Do you want to throw some kind of 'not implemented' here?

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
pkg/kernel/lib/interpreter/interpreter.dart:234: defaultStatement(node, env);
I don't think this should occur, so we could just throw if it does.

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
pkg/kernel/lib/interpreter/interpreter.dart:236:
visitExpressionStatement(ExpressionStatement node, env) =>
As a style issue, I would suggest to make either all of the visit methods use =>
bodies or make all of them use { } bodies.

It might be convenient to have an eval method on this class.

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
pkg/kernel/lib/interpreter/interpreter.dart:257: Value value =
evaluator.eval(node.initializer ?? new NullLiteral(), env);
It amounts to the same thing, but we probably want to write this as:

Value value = node.initializer != null
    ? eval(node.initializer, env)
    : Value.nullInstance;

Which has the advantage of being compositional (only recurring on proper
subparts of the input).  This normally ends up making reasoning about the
semantics easier.

[zhivkag, 2017-03-28 08:21:31]

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
File pkg/kernel/lib/interpreter/interpreter.dart (right):

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
pkg/kernel/lib/interpreter/interpreter.dart:232: defaultStatement(Statement
node, env) {}
On 2017/03/28 07:11:21, Kevin Millikin (Google) wrote:
> Do you want to throw some kind of 'not implemented' here?

Done.

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
pkg/kernel/lib/interpreter/interpreter.dart:234: defaultStatement(node, env);
On 2017/03/28 07:11:21, Kevin Millikin (Google) wrote:
> I don't think this should occur, so we could just throw if it does.

Done.

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
pkg/kernel/lib/interpreter/interpreter.dart:236:
visitExpressionStatement(ExpressionStatement node, env) =>
On 2017/03/28 07:11:21, Kevin Millikin (Google) wrote:
> As a style issue, I would suggest to make either all of the visit methods use
=>
> bodies or make all of them use { } bodies.
> 
> It might be convenient to have an eval method on this class.

Done.

https://codereview.chromium.org/2775293002/diff/1/pkg/kernel/lib/interpreter/...
pkg/kernel/lib/interpreter/interpreter.dart:257: Value value =
evaluator.eval(node.initializer ?? new NullLiteral(), env);
On 2017/03/28 07:11:21, Kevin Millikin (Google) wrote:
> It amounts to the same thing, but we probably want to write this as:
> 
> Value value = node.initializer != null
>     ? eval(node.initializer, env)
>     : Value.nullInstance;
> 
> Which has the advantage of being compositional (only recurring on proper
> subparts of the input).  This normally ends up making reasoning about the
> semantics easier.

Done.

[zhivkag, 2017-03-28 08:23:26]

Description was changed from

==========
Implements simple statement executer

This change adds support for executing:
 - BlockStatement
 - ExpressionStatement
 - IfStatement
 - VariableDeclaration

Currently only BlockStatement introduces a new environment and
VariableDeclaration modifies the environment.

BUG=
==========

to

==========
Implements simple statement executer

This change adds support for executing:
 - BlockStatement
 - ExpressionStatement
 - IfStatement
 - VariableDeclaration

Currently only BlockStatement introduces a new environment and
VariableDeclaration modifies the environment.

BUG=
R=kmillikin@google.com

Committed:
https://github.com/dart-lang/sdk/commit/23cc114c2f61596f5b168cd3b08107c03851bbbe
==========

[zhivkag, 2017-03-28 08:23:27]

Committed patchset #2 (id:20001) manually as
23cc114c2f61596f5b168cd3b08107c03851bbbe (presubmit successful).