1099252-Check that alignment is a 'good' constant (changeset 1394370)

Src/Compilers/CSharp/Portable/Binder/Binder_InterpolatedString.cs

@@ -39,16 +39,17 @@ private BoundExpression BindInterpolatedString(InterpolatedStringExpressionSynta
                             if (interpolation.AlignmentClause != null)
                             {
                                 alignment = GenerateConversionForAssignment(intType, BindValue(interpolation.AlignmentClause.Value, diagnostics, Binder.BindValueKind.RValue), diagnostics);
-                                if (alignment.ConstantValue != null)
+                                var alignmentConstant = alignment.ConstantValue;
+                                if (alignmentConstant != null && !alignmentConstant.IsBad)
                                 {
                                     const int magnitudeLimit = 32767;
                                     // check that the magnitude of the alignment is "in range".
-                                    int alignmentValue = alignment.ConstantValue.Int32Value;
+                                    int alignmentValue = alignmentConstant.Int32Value;
                                     //  We do the arithmetic using negative numbers because the largest negative int has no corresponding positive (absolute) value.
                                     alignmentValue = (alignmentValue > 0) ? -alignmentValue : alignmentValue;
                                     if (alignmentValue < -magnitudeLimit)
                                     {
-                                        diagnostics.Add(ErrorCode.WRN_AlignmentMagnitude, alignment.Syntax.Location, alignment.ConstantValue.Int32Value, magnitudeLimit);
+                                        diagnostics.Add(ErrorCode.WRN_AlignmentMagnitude, alignment.Syntax.Location, alignmentConstant.Int32Value, magnitudeLimit);
                                     }
                                 }
                                 else if (!alignment.HasErrors)

Src/Compilers/CSharp/Test/Semantic/Semantics/InterpolationTests.cs

@@ -1083,5 +1083,28 @@ public static void Main(string[] args)
 -System.String[]-");
         }
 
+        [WorkItem(1097386, "DevDiv")]
+        [Fact]
+        public void Dynamic01()
+        {
+            var text =
+@"class C
+{
+    const dynamic a = a;
+    string s = $""{0,a}"";
+}";
+            CreateCompilationWithMscorlibAndSystemCore(text).VerifyDiagnostics(
+                // (3,19): error CS0110: The evaluation of the constant value for 'C.a' involves a circular definition
+                //     const dynamic a = a;
+                Diagnostic(ErrorCode.ERR_CircConstValue, "a").WithArguments("C.a").WithLocation(3, 19),
+                // (3,23): error CS0134: 'C.a' is of type 'dynamic'. A const field of a reference type other than string can only be initialized with null.
+                //     const dynamic a = a;
+                Diagnostic(ErrorCode.ERR_NotNullConstRefField, "a").WithArguments("C.a", "dynamic").WithLocation(3, 23),
+                // (4,21): error CS0150: A constant value is expected
+                //     string s = $"{0,a}";
+                Diagnostic(ErrorCode.ERR_ConstantExpected, "a").WithLocation(4, 21)
+                );
+        }
+
     }
 }