Transating checked assignments using checked {} code blocks

Author: SteveWilkes

ReadableExpressions.UnitTests/WhenTranslatingAssignments.cs

@@ -39,7 +39,7 @@ public void ShouldTranslateACheckedAdditionAssignment()
 
             var translated = addTenAndAssign.ToReadableString();
 
-            Assert.AreEqual("i += 10", translated);
+            Assert.AreEqual("checked { i += 10 }", translated);
         }
 
         [TestMethod]
@@ -61,7 +61,7 @@ public void ShouldTranslateACheckedSubtractionAssignment()
 
             var translated = substractOneAndAssign.ToReadableString();
 
-            Assert.AreEqual("i -= 1", translated);
+            Assert.AreEqual("checked { i -= 1 }", translated);
         }
 
         [TestMethod]
@@ -83,7 +83,7 @@ public void ShouldTranslateACheckedMultiplicationAssignment()
 
             var translated = doubleAndAssign.ToReadableString();
 
-            Assert.AreEqual("i *= 2", translated);
+            Assert.AreEqual("checked { i *= 2 }", translated);
         }
 
         [TestMethod]

ReadableExpressions/StringExtensions.cs

@@ -38,7 +38,7 @@ public static string Indent(this string line)
                 return string.Empty;
             }
 
-            if (line.Contains(Environment.NewLine))
+            if (line.IsMultiLine())
             {
                 return string.Join(
                     Environment.NewLine,
@@ -48,6 +48,8 @@ public static string Indent(this string line)
             return IndentSpaces + line;
         }
 
+        public static bool IsMultiLine(this string value) => value.Contains(Environment.NewLine);
+
         private const string UnindentPlaceholder = "*unindent*";
 
         public static string Unindented(this string line)

ReadableExpressions/Translators/AssignmentExpressionTranslator.cs

@@ -1,5 +1,6 @@
 namespace AgileObjects.ReadableExpressions.Translators
 {
+    using System;
     using System.Collections.Generic;
     using System.Linq;
     using System.Linq.Expressions;
@@ -26,6 +27,11 @@ internal class AssignmentExpressionTranslator : ExpressionTranslatorBase
                 [ExpressionType.SubtractAssignChecked] = "-="
             };
 
+        private static readonly ExpressionType[] _checkedAssignmentTypes = _symbolsByNodeType
+            .Keys
+            .Where(nt => nt.ToString().EndsWith("Checked", StringComparison.Ordinal))
+            .ToArray();
+
         private readonly DefaultExpressionTranslator _defaultTranslator;
 
         internal AssignmentExpressionTranslator(DefaultExpressionTranslator defaultTranslator)
@@ -54,7 +60,11 @@ internal string GetAssignment(
                 ? _defaultTranslator.Translate((DefaultExpression)value)
                 : GetValueTranslation(value, context);
 
-            return $"{target} {symbol} {valueString}";
+            var assignment = $"{target} {symbol} {valueString}";
+
+            assignment = AdjustForCheckedAssignmentIfAppropriate(assignment, assignmentType);
+
+            return assignment;
         }
 
         private string GetValueTranslation(Expression value, TranslationContext context)
@@ -73,5 +83,26 @@ private string GetValueTranslation(Expression value, TranslationContext context)
 
             return valueBlock.WithReturn().WithParentheses();
         }
+
+        private static string AdjustForCheckedAssignmentIfAppropriate(
+            string assignment,
+            ExpressionType assignmentType)
+        {
+            if (!_checkedAssignmentTypes.Contains(assignmentType))
+            {
+                return assignment;
+            }
+
+            if (assignment.IsMultiLine())
+            {
+                return $@"
+checked
+{{
+{assignment.Indent()}
+}}".TrimStart();
+            }
+
+            return $"checked {{ {assignment} }}";
+        }
     }
 }

ReadableExpressions/Translators/Formatting/FormattableExpressionBase.cs

@@ -17,7 +17,7 @@ protected string GetFormattedTranslation()
         {
             var translation = SingleLineTranslationFactory.Invoke();
 
-            return (translation.Length > 100) || translation.Contains(Environment.NewLine)
+            return (translation.Length > 100) || translation.IsMultiLine()
                 ? MultipleLineTranslationFactory.Invoke()
                 : translation;
         }