Infer types of bool/null/string literals.

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

Index: pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
index 6f57f7d708a8a63a349517cdfe465a218a761e68..386b47a6ce08ace6154d1e2d6c7579cfddf65652 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
@@ -35,6 +35,17 @@ class KernelBlock extends Block implements KernelStatement {
   }
 }
 
+/// Concrete shadow object representing a boolean literal in kernel form.
+class KernelBoolLiteral extends BoolLiteral implements KernelExpression {
+  KernelBoolLiteral(bool value) : super(value);
+
+  @override
+  DartType _inferExpression(
+      KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
+    return inferrer.inferBoolLiteral(typeContext, typeNeeded);
+  }
+}
+
 /// Concrete shadow object representing a double literal in kernel form.
 class KernelDoubleLiteral extends DoubleLiteral implements KernelExpression {
   KernelDoubleLiteral(double value) : super(value);
@@ -225,6 +236,29 @@ class KernelStaticGet extends StaticGet implements KernelExpression {
   }
 }
 
+/// Concrete shadow object representing a string concatenation in kernel form.
+class KernelStringConcatenation extends StringConcatenation
+    implements KernelExpression {
+  KernelStringConcatenation(List<Expression> expressions) : super(expressions);
+
+  @override
+  DartType _inferExpression(
+      KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
+    return inferrer.inferStringLiteral(typeContext, typeNeeded);

[Paul Berry, 2017/05/01 22:03:44]

This works for now, but in the long run it will need to recurse into the
subexpressions in order to handle stuff like:

f(x) {
  if (x is int) {
    return "$x"; // (1)
  }
}

(the kernel object for the reference to `x` at (1) needs to have its
promotedType field set to `int`, and that will only happen if we recurse into
the subexpression).

Would you mind adding a TODO comment?

[scheglov, 2017/05/02 02:35:20]

Done.
I ended up removing testing for StringConcatenation at all, because with
analyzer we do report the promoted type, but not in front_end yet.

+  }
+}
+
+/// Concrete shadow object representing a string literal in kernel form.
+class KernelStringLiteral extends StringLiteral implements KernelExpression {
+  KernelStringLiteral(String value) : super(value);
+
+  @override
+  DartType _inferExpression(
+      KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
+    return inferrer.inferStringLiteral(typeContext, typeNeeded);
+  }
+}
+
 /// Concrete implementation of [TypeInferenceEngine] specialized to work with
 /// kernel objects.
 class KernelTypeInferenceEngine extends TypeInferenceEngineImpl<KernelField> {