Setup type and modifiers of local variables on creation.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 97e7af17d8020cc2b7ec5a0481a724cbc67e6da4..14f21a21d86d667e04693831fd62ae42470241e4 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -126,6 +126,10 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
 
   bool constantExpressionRequired = false;
 
+  DartType currentLocalVariableType = const DynamicType();
+
+  int currentLocalVariableModifiers = -1;
+
   BodyBuilder(
       KernelLibraryBuilder library,
       this.member,
@@ -899,15 +903,27 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void endVariableInitializer(Token assignmentOperator) {
     debugEvent("VariableInitializer");
     assert(assignmentOperator.stringValue == "=");
-    Expression initializer = popForValue();
-    Identifier identifier = pop();
-    push(new VariableDeclaration(identifier.name, initializer: initializer)
-      ..fileEqualsOffset = assignmentOperator.charOffset);
+    pushNewLocalVariable(popForValue(),
+        equalsCharOffset: assignmentOperator.charOffset);
   }
 
   @override
   void handleNoVariableInitializer(Token token) {
     debugEvent("NoVariableInitializer");
+    pushNewLocalVariable(null);
+  }
+
+  void pushNewLocalVariable(Expression initializer,
+      {int equalsCharOffset: TreeNode.noOffset}) {
+    Identifier identifier = pop();
+    bool isConst = (currentLocalVariableModifiers & constMask) != 0;

[karlklose, 2017/03/23 09:52:15]

assert(currentLocalVariableModifiers != -1) here?

[ahe, 2017/03/23 11:17:54]

Done.

+    bool isFinal = (currentLocalVariableModifiers & finalMask) != 0;
+    assert(isConst == constantExpressionRequired);
+    push(new VariableDeclaration(identifier.name,
+        initializer: initializer,
+        type: currentLocalVariableType,
+        isFinal: isFinal,
+        isConst: isConst)..fileEqualsOffset = equalsCharOffset);
   }
 
   @override
@@ -927,15 +943,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void endInitializedIdentifier(Token nameToken) {
     // TODO(ahe): Use [InitializedIdentifier] here?
     debugEvent("InitializedIdentifier");
-    TreeNode node = pop();
-    VariableDeclaration variable;
-    if (node is VariableDeclaration) {
-      variable = node;
-    } else if (node is Identifier) {
-      variable = new VariableDeclaration(node.name);
-    } else {
-      internalError("unhandled identifier: ${node.runtimeType}");
-    }
+    VariableDeclaration variable = pop();
     variable.fileOffset = nameToken.charOffset;
     push(variable);
     scope[variable.name] = new KernelVariableBuilder(
@@ -943,22 +951,25 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   @override
+  void beginVariablesDeclaration(Token token) {
+    debugEvent("beginVariablesDeclaration");
+    DartType type = pop();
+    int modifiers = Modifier.validate(pop());
+    super.push(currentLocalVariableModifiers);

[Paul Berry, 2017/03/23 10:50:52]

Why not:

push(currentLocalVariableModifiers ?? NullValue.LocalVariableModifiers);

(and add `LocalVariableModifiers` to the `NullValue` enum)

[ahe, 2017/03/23 11:17:55]

I need to use super.push to avoid changing inInitializer. I'll look into
cleaning that up.

Based on some old advice regarding performance, I'm avoiding initializing an int
field to null, hence currentLocalVariableModifiers can't be null.

+    super.push(currentLocalVariableType);

[Paul Berry, 2017/03/23 10:50:52]

Similar question here.

[ahe, 2017/03/23 11:17:55]

I'll change it to ?? NullValue.Type.

+    currentLocalVariableType = type ?? const DynamicType();

[Paul Berry, 2017/03/23 10:50:52]

FYI, for type inference we will need to keep track of whether an explicit type
was provided, so consider moving the `?? const DynamicType()` to line 924.

[ahe, 2017/03/23 11:17:54]

Done.

+    currentLocalVariableModifiers = modifiers;
+    super.push(constantExpressionRequired);

[Paul Berry, 2017/03/23 10:50:52]

AFAICT, `constantExpressionRequired` is never null, so I think we can do:

push(constantExpressionRequired)

[ahe, 2017/03/23 11:17:54]

As mentioned above, super.push is used to avoid interfering with inInitializer.

+    constantExpressionRequired = (modifiers & constMask) != 0;
+  }
+
+  @override
   void endVariablesDeclaration(int count, Token endToken) {
     debugEvent("VariablesDeclaration");
     List<VariableDeclaration> variables = popList(count);
-    DartType type = pop();
-    int modifiers = Modifier.validate(pop());
-    bool isConst = (modifiers & constMask) != 0;
-    bool isFinal = (modifiers & finalMask) != 0;
-    if (type != null || isConst || isFinal) {
-      type ??= const DynamicType();
-      for (VariableDeclaration variable in variables) {
-        variable
-          ..type = type
-          ..isConst = isConst
-          ..isFinal = isFinal;
-      }
-    }
+    constantExpressionRequired = pop();
+    currentLocalVariableType = pop();
+    currentLocalVariableModifiers = pop();
     if (variables.length != 1) {
       push(variables);
     } else {