Reduce strong mode errors and warnings

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 881d8f3cdd4b486557a0ad43ae39a5a349b640ba..25e2299d5e346f5214e5828e3767dbacf29e5225 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -224,13 +224,14 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   Block popBlock(int count) {
-    List<Statement> statements = popList(count) ?? <Statement>[];
+    List statements = popList(count) ?? <Statement>[];

[Siggi Cherem (dart-lang), 2017/02/02 04:26:58]

this is a temporary way of hiding some errors, but not the ideal fix. I think
here (as well as in how we process optional arguments) we might need a different
way to represent this kind of union type.

Note that this change (and the related changes below) produce warnings in strong
mode, but at least not an error.

[ahe, 2017/02/02 07:28:30]

I'm strongly opposed to removing types to appease a buggy type checker.

[Siggi Cherem (dart-lang), 2017/02/02 16:30:35]

in this case I don't believe it's a bug in the checker: it seems that the type
is actually not accurate in this case. The `statements` variable is not a
List<Statement>, but a List< {Statement | List<Statement> } >, correct?

     List<Statement> copy;
     for (int i = 0; i < statements.length; i++) {
       var statement = statements[i];
       if (statement is List) {
         copy ??= new List<Statement>.from(statements.getRange(0, i));
-        copy.addAll(statement);
+        List<Statement> subStatements = statement;
+        copy.addAll(subStatements);
       } else if (copy != null) {
         copy.add(statement);
       }
@@ -459,7 +460,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void endArguments(int count, Token beginToken, Token endToken) {
     debugEvent("Arguments");
-    List arguments = popList(count) ?? <Expression>[];
+    List<Expression> arguments = popList(count) ?? <Expression>[];
     int firstNamedArgument = arguments.length;
     for (int i = 0; i < arguments.length; i++) {
       var node = arguments[i];
@@ -493,7 +494,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void endSend(Token token) {
     debugEvent("Send");
     Arguments arguments = pop();
-    List typeArguments = pop();
+    List<DartType> typeArguments = pop();
     Object receiver = pop();
     if (arguments != null && typeArguments != null) {
       arguments.types.addAll(typeArguments);
@@ -989,7 +990,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     if (variableOrExpression is VariableDeclaration) {
       variables.add(variableOrExpression);
     } else if (variableOrExpression is List) {
-      variables.addAll(variableOrExpression);
+      List<VariableDeclaration> vars = variableOrExpression;

[Siggi Cherem (dart-lang), 2017/02/02 04:26:58]

This has an implicit downcast warning, without this fix, the argument couldn't
be assigned to the `addAll` below.

An alternative here would be to change the is check to `is
List<VariableDeclaration>` - that would work if the list has the reified type,
which I think it does.

[ahe, 2017/02/02 07:28:30]

Implicit downcast warning?!?

[kasperl, 2017/02/02 07:51:30]

Is this the warning that will go away when we implement the correct runtime
checks in Dart 2.0? See https://github.com/dart-lang/sdk/issues/28588.

[Siggi Cherem (dart-lang), 2017/02/06 23:35:50]

It's quite related, but there is an extra nuance here because the argument is
List and the parameter is Iterable. I filed this bug to the language team:
https://github.com/dart-lang/sdk/issues/28651

For now, I made a small change here to introduce an intermediate assignment to
Iterable to turn the error into a warning that we ignore and a TODO to remove
it.

+      variables.addAll(vars);
     } else if (variableOrExpression == null) {
       // Do nothing.
     } else if (variableOrExpression is Expression) {
@@ -1189,7 +1191,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       push(name.buildTypesWithBuiltArguments(arguments));
     } else if (name is TypeDeclarationBuilder) {
       push(name.buildTypesWithBuiltArguments(arguments));
-    } else if (name is TypeBuilder) {
+    } else if (name is KernelTypeBuilder) {

[Siggi Cherem (dart-lang), 2017/02/02 04:26:58]

.build is not defined in TypeBuilder - I was expecting the error to be visible
also without strong mode, but it wasn't

[ahe, 2017/02/02 07:28:30]

This fix isn't correct. It potentially causes a TypeBuilder to passed to
toKernelType.

[Siggi Cherem (dart-lang), 2017/02/02 16:30:35]

Shold `TypeBuilder` declare a `build()` method instead?

[Siggi Cherem (dart-lang), 2017/02/06 23:35:50]

Done - I added `build()` to TypeBuilder as discussed. I didn't have a return
type for it though, I left it dynamic but let me know if there is something
better for it.

       push(name.build());
     } else {
       push(toKernelType(name, arguments));
@@ -1269,7 +1271,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
             name.fileOffset);
       }
       if (thisKeyword == null) {
-        variable = builder.build();
+        KernelFormalParameterBuilder formalBuilder = builder;
+        variable = formalBuilder.build();
         variable.initializer = name.initializer;
       } else if (builder.isField && builder.parent == classBuilder) {
         FieldBuilder field = builder;
@@ -1609,7 +1612,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     debugEvent("NewExpression");
     Arguments arguments = pop();
     String name = pop();
-    List typeArguments = pop();
+    List<DartType> typeArguments = pop();
     var type = pop();
 
     if (typeArguments != null) {
@@ -1618,7 +1621,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     }
 
     String errorName;
-    if (type is ClassBuilder) {
+    if (type is KernelClassBuilder) {
       Builder b = type.findConstructorOrFactory(name);
       Member target;
       if (b == null) {
@@ -1731,7 +1734,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       exitLocalScope();
     }
     FormalParameters formals = pop();
-    List typeParameters = pop();
+    List<TypeParameter> typeParameters = pop();
     push(formals.addToFunction(new FunctionNode(body,
                 typeParameters: typeParameters, asyncMarker: asyncModifier)));
     functionNestingLevel--;
@@ -1757,7 +1760,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     AsyncMarker asyncModifier = pop();
     exitLocalScope();
     FormalParameters formals = pop();
-    List typeParameters = pop();
+    List<TypeParameter> typeParameters = pop();
     FunctionNode function = formals.addToFunction(new FunctionNode(body,
             typeParameters: typeParameters, asyncMarker: asyncModifier));
     push(new FunctionExpression(function));