feat: pizza example, maybe needs work

Author: thygrrr

NewType.Generator/NUGET.md

@@ -12,18 +12,37 @@ dotnet add package newtype
 
 ## Usage
 
-#### Basic: strongly typed `string`-names, `int`-IDs, and `int`-counts
+#### Basic: typed IDs and counts
 ```csharp
 using newtype;
 
+[newtype<string>]
+public readonly partial struct TableId;
+
 [newtype<int>]
-public readonly partial struct Pizzas;
+public readonly partial struct PizzasEaten;
 
 [newtype<double>]
 public readonly partial struct Fullness;
+
+class Guest
+{
+    TableId table = "Table 1";
+    PizzasEaten pizzasEaten;
+    Fullness fullness;
+    
+    public void fillEmUp(Fullness threshold)
+    {
+        while (fullness < threshold)
+        {
+            pizzasEaten++;
+            fullness += 0.1;
+        }
+    }
+}
 ```
 
-#### Typical: quantities backed by the same data type. 
+#### Typical: quantities backed by the same data type but distinct domain semantics
 *For example, forces, velocities, positions, etc. all lose their semantics when expressed as `Vector3`*
 ```csharp
 using System.Numerics;

NewType.Tests/GeneratorTests/ReadmeExampleTests.cs

@@ -0,0 +1,93 @@
+using Xunit;
+
+namespace newtype.tests;
+
+public class ReadmeExampleTests
+{
+    private const string ReadmeSource = """
+        using newtype;
+
+        [newtype<string>]
+        public readonly partial struct TableId;
+
+        [newtype<int>]
+        public readonly partial struct PizzasEaten;
+
+        [newtype<double>]
+        public readonly partial struct Fullness;
+
+        class Guest
+        {
+            TableId table = "Table 1";
+            PizzasEaten pizzasEaten;
+            Fullness fullness;
+
+            public void fillEmUp(Fullness threshold)
+            {
+                while (fullness < threshold)
+                {
+                    pizzasEaten++;
+                    fullness += 0.1;
+                }
+            }
+        }
+        """;
+
+    [Fact]
+    public void Readme_Example_Compiles_Without_Errors()
+    {
+        var result = GeneratorTestHelper.RunGenerator(ReadmeSource);
+
+        // Attribute + 3 aliases
+        Assert.Equal(4, result.GeneratedTrees.Length);
+
+        var sources = result.Results[0].GeneratedSources;
+        Assert.Single(sources.Where(s => s.HintName.EndsWith("TableId.g.cs")));
+        Assert.Single(sources.Where(s => s.HintName.EndsWith("PizzasEaten.g.cs")));
+        Assert.Single(sources.Where(s => s.HintName.EndsWith("Fullness.g.cs")));
+    }
+
+    [Fact]
+    public void TableId_Has_String_Backing_And_Implicit_Conversion()
+    {
+        var result = GeneratorTestHelper.RunGenerator(ReadmeSource);
+        var text = GetGeneratedText(result, "TableId.g.cs");
+
+        Assert.Contains("private readonly string _value;", text);
+        Assert.Contains("public static implicit operator TableId(string value)", text);
+        Assert.Contains("public static implicit operator string(TableId value)", text);
+    }
+
+    [Fact]
+    public void PizzasEaten_Has_Int_Backing_And_Arithmetic()
+    {
+        var result = GeneratorTestHelper.RunGenerator(ReadmeSource);
+        var text = GetGeneratedText(result, "PizzasEaten.g.cs");
+
+        Assert.Contains("private readonly int _value;", text);
+        // ++ works via implicit conversion to int and back
+        Assert.Contains("public static implicit operator PizzasEaten(int value)", text);
+        Assert.Contains("public static implicit operator int(PizzasEaten value)", text);
+        Assert.Contains("operator +", text);
+    }
+
+    [Fact]
+    public void Fullness_Has_Comparison_And_Addition()
+    {
+        var result = GeneratorTestHelper.RunGenerator(ReadmeSource);
+        var text = GetGeneratedText(result, "Fullness.g.cs");
+
+        Assert.Contains("private readonly double _value;", text);
+        Assert.Contains("operator <", text);
+        Assert.Contains("operator +", text);
+    }
+
+    private static string GetGeneratedText(
+        Microsoft.CodeAnalysis.GeneratorDriverRunResult result,
+        string hintNameSuffix)
+    {
+        return result.Results[0].GeneratedSources
+            .Single(s => s.HintName.EndsWith(hintNameSuffix))
+            .SourceText.ToString();
+    }
+}

README.md

@@ -18,7 +18,7 @@ dotnet add package newtype
 
 ## Usage
 
-#### Basic: strongly typed `string`-names, `int`-IDs, and `int`-counts
+#### Basic: typed IDs and counts
 ```csharp
 using newtype;
 
@@ -48,7 +48,7 @@ class Guest
 }
 ```
 
-#### Typical: quantities backed by the same data type.
+#### Typical: quantities backed by the same data type but distinct domain semantics
 *For example, forces, velocities, positions, etc. all lose their semantics when expressed as `Vector3`*
 ```csharp
 using System.Numerics;