Issue 29358. Fix for reporting constant errors while evaluating constructor invocations.

pkg/analyzer/lib/src/error/codes.dart

Index: pkg/analyzer/lib/src/error/codes.dart
diff --git a/pkg/analyzer/lib/src/error/codes.dart b/pkg/analyzer/lib/src/error/codes.dart
index 48df41b741e95b3072131ecdaf979932f813baa8..f86f0d9608e9bcf4afdf224d052966fd7011d173 100644
--- a/pkg/analyzer/lib/src/error/codes.dart
+++ b/pkg/analyzer/lib/src/error/codes.dart
@@ -51,6 +51,14 @@ class CheckedModeCompileTimeErrorCode extends ErrorCode {
           "'{1}'.");
 
   /**
+   * 16.12.2 Const: It is a compile-time error if evaluation of a constant
+   * object results in an uncaught exception being thrown.
+   */
+  static const CheckedModeCompileTimeErrorCode CONST_EVAL_THROWS_EXCEPTION =
+      const CheckedModeCompileTimeErrorCode('CONST_EVAL_THROWS_EXCEPTION',
+          "Evaluation of this constant expression throws an exception.");

[Brian Wilkerson, 2017/04/18 18:53:21]

I can't see, from the tests, where the error is being reported, so it might not
be as bad as I'm imagining, but this seems vague. Longer term (not for this CL),
is there any reasonable way for us to give more actionable feedback (don't pass
this value for this argument) or more compete information (such as where the
exception will be thrown).

[scheglov, 2017/04/18 19:11:03]

Potentially it would be a sequence of places, and/or several reasons at several
places.

For example:

class A {
  const A() : v = new Object();
  final v;
}

class B {
  const B() : a = const A();
  final a;
}

class C {
  const C() : b = const B();
  final b;
}

const c = const C();

We will report an error for the top-level variable "c".
The actual problem is however in A (new Object() instead of const Object()).
Not quite this error code, but I think you get the idea.

+
+  /**
    * 7.6.1 Generative Constructors: In checked mode, it is a dynamic type error
    * if o is not <b>null</b> and the interface of the class of <i>o</i> is not a
    * subtype of the static type of the field <i>v</i>.