[cfe] Add MacroAnnotationParser to support early recognition

This CL adds a parser listener that supports (the initial) part of
the syntax needed to support detection of macro application early in
the pipeline. The listener is deliberately implementing (as opposed to
extending) the listener interface to ensure that all case handled in
the listener itself. The listener keeps track of whether unsupported
constructs have been seen to ensure that only valid syntax results
in a macro application.

Change-Id: I6742a0daa39c80f09759b41b9abdd7e693da4cc0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/225723
Reviewed-by: Chloe Stefantsova <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>

Author: johnniwinther

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

@@ -395,6 +395,7 @@ class KernelTarget extends TargetImplementation {
       List<SourceClassBuilder> sourceClassBuilders =
           loader.checkSemantics(objectClassBuilder);
       loader.computeMacroDeclarations(sourceClassBuilders);
+      loader.computeMacroApplications();
       loader.finishTypeVariables(objectClassBuilder, dynamicType);
       loader.createTypeInferenceEngine();
       loader.buildComponent();
@@ -416,7 +417,6 @@ class KernelTarget extends TargetImplementation {
       loader.checkMixins(sourceClassBuilders);
       loader.buildOutlineExpressions(
           loader.coreTypes, synthesizedFunctionNodes);
-      loader.computeMacroApplications();
       loader.checkTypes();
       loader.checkRedirectingFactories(sourceClassBuilders);
       loader.checkMainMethods();

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

@@ -21,11 +21,19 @@ class MacroApplicationData {
 }
 
 class MacroApplications {
-  final List<Class> macros;
+  final List<MacroApplication> macros;
 
   MacroApplications(this.macros);
 }
 
+class MacroApplication {
+  final Class cls;
+  final String constructorName;
+  // TODO(johnniwinther): Add support for arguments.
+
+  MacroApplication(this.cls, this.constructorName);
+}
+
 class LibraryMacroApplicationData {
   Map<Class, ClassMacroApplicationData> classData = {};
   Map<Member, MacroApplications> memberApplications = {};