Use messages for (some) public API errors

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

Index: pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
index 31200547b5e0ad5e4769f939bda2f432993e8ad2..31f0df5cba96ff2f8c8472cbf1234bcfd791fc17 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
@@ -97,7 +97,7 @@ class KernelTarget extends TargetImplementation {
 
   Program program;
 
-  final List<String> errors = <String>[];
+  final List<LocatedMessage> errors = <LocatedMessage>[];

[Siggi Cherem (dart-lang), 2017/07/12 00:35:15]

note: this is now possible because I made deprecated_InputError implement
LocatedMessage

[ahe, 2017/07/12 13:14:43]

I'd like to hold back on this change. I'm pretty close to achieving the same
effect, but without making deprecated_InputError implement LocatedMessage.

[Siggi Cherem (dart-lang), 2017/07/12 21:54:59]

OK, I reverted this.

 
   final TypeBuilder dynamicType =
       new KernelNamedTypeBuilder("dynamic", null, -1, null);
@@ -120,9 +120,8 @@ class KernelTarget extends TargetImplementation {
     Uri uri = file is String ? Uri.parse(file) : file;
     deprecated_InputError error =
         new deprecated_InputError(uri, charOffset, message);
-    String formatterMessage = error.deprecated_format();
-    print(formatterMessage);
-    errors.add(formatterMessage);
+    errors.add(error);
+    print(error.deprecated_format());

[ahe, 2017/07/12 13:14:43]

I'm pretty close to removing this and all the other calls to print from this
class.

[Siggi Cherem (dart-lang), 2017/07/12 21:54:59]

fantastic!, reverted to prevent conflicts.

   }
 
   SourceLoader<Library> createLoader() =>
@@ -220,9 +219,8 @@ class KernelTarget extends TargetImplementation {
 
   void handleInputError(deprecated_InputError error, {bool isFullProgram}) {
     if (error != null) {
-      String message = error.deprecated_format();
-      print(message);
-      errors.add(message);
+      errors.add(error);
+      print(error.deprecated_format());
     }
     program = erroneousProgram(isFullProgram);
   }
@@ -311,9 +309,9 @@ class KernelTarget extends TargetImplementation {
     }
     List<Expression> expressions = <Expression>[];
     for (LocatedMessage error in recoverableErrors) {
+      errors.add(error);
       String message = deprecated_formatUnexpected(
           error.uri, error.charOffset, error.message);
-      errors.add(message);
       expressions.add(new StringLiteral(message));
     }
     mainLibrary.library.addMember(new Field(new Name("#errors"),
@@ -335,8 +333,8 @@ class KernelTarget extends TargetImplementation {
       KernelProcedureBuilder mainBuilder = new KernelProcedureBuilder(null, 0,
           null, "main", null, null, ProcedureKind.Method, library, -1, -1, -1);
       library.addBuilder(mainBuilder.name, mainBuilder, -1);
-      mainBuilder.body = new ExpressionStatement(
-          new Throw(new StringLiteral("${errors.join('\n')}")));
+      mainBuilder.body = new ExpressionStatement(new Throw(
+          new StringLiteral("${errors.map((e) => e.message).join('\n')}")));

[Siggi Cherem (dart-lang), 2017/07/12 00:35:15]

this changes the generated code a bit, one of our tests shows the difference in
the `.expect` files.

[ahe, 2017/07/12 13:14:43]

What's currently stored in the .expect files helps me catch problems when I
break the compiler's output. One can argue that it isn't the purpose of the
.expect files, but as I consider alternative, I'm actually starting to believe
that having formatted messages in the .expect files is a convenient way to
ensure that everything works as intended.

[Siggi Cherem (dart-lang), 2017/07/12 21:54:59]

reverted this for now as well

     }
     library.build(loader.coreLibrary);
     return link(<Library>[library.library]);
@@ -639,7 +637,7 @@ class KernelTarget extends TargetImplementation {
 
   void verify() {
     var verifyErrors = verifyProgram(program);
-    errors.addAll(verifyErrors.map((error) => '$error'));
+    errors.addAll(verifyErrors);
     ticker.logMs("Verified program");
   }