Review fixes.

src/WpfMath/Atoms/BigOperatorAtom.cs

@@ -91,8 +91,7 @@ protected override Box CreateBoxCore(TexEnvironment environment)
             // Make all component boxes equally wide.
             var maxWidth = Math.Max(Math.Max(baseBox.Width, upperLimitBox == null ? 0 : upperLimitBox.Width),
                 lowerLimitBox == null ? 0 : lowerLimitBox.Width);
-            if (baseBox != null)
-                baseBox = ChangeWidth(baseBox, maxWidth);
+            baseBox = ChangeWidth(baseBox, maxWidth);
             if (upperLimitBox != null)
                 upperLimitBox = ChangeWidth(upperLimitBox, maxWidth);
             if (lowerLimitBox != null)
@@ -114,7 +113,7 @@ protected override Box CreateBoxCore(TexEnvironment environment)
             }
 
             // Add box for base atom.
-            resultBox.Add(baseBox!);
+            resultBox.Add(baseBox);
 
             // Create and add box for lower limit.
             if (this.LowerLimitAtom != null)
@@ -127,7 +126,7 @@ protected override Box CreateBoxCore(TexEnvironment environment)
             }
 
             // Adjust height and depth of result box.
-            var baseBoxHeight = baseBox!.Height;
+            var baseBoxHeight = baseBox.Height;
             var totalHeight = resultBox.Height + resultBox.Depth;
             if (upperLimitBox != null)
                 baseBoxHeight += opSpacing5 + kern + upperLimitBox.Height + upperLimitBox.Depth;

src/WpfMath/Atoms/CharAtom.cs

@@ -17,15 +17,13 @@ public CharAtom(SourceSpan? source, char character, string? textStyle = null)
         // Null means default text style.
         public string? TextStyle { get; }
 
-        private bool IsDefaultTextStyle => this.TextStyle == null;
-
         public override ITeXFont GetStyledFont(TexEnvironment environment) =>
             this.TextStyle == TexUtilities.TextStyleName ? environment.TextFont : base.GetStyledFont(environment);
 
         protected override Result<CharInfo> GetCharInfo(ITeXFont texFont, TexStyle style) =>
-            this.IsDefaultTextStyle
+            this.TextStyle == null
                 ? texFont.GetDefaultCharInfo(this.Character, style)
-                : texFont.GetCharInfo(this.Character, this.TextStyle!, style); // Nullable: CS8604, could be resolved by inlining IsDefaultTextStyle
+                : texFont.GetCharInfo(this.Character, this.TextStyle, style);
 
         public override Result<CharFont> GetCharFont(ITeXFont texFont) =>
             // Style is irrelevant here.

src/WpfMath/Atoms/Radical.cs

@@ -13,14 +13,14 @@ internal class Radical : Atom
 
         private const double scale = 0.55;
 
-        public Radical(SourceSpan? source, Atom? baseAtom, Atom? degreeAtom = null)
+        public Radical(SourceSpan? source, Atom baseAtom, Atom? degreeAtom = null)
             : base(source)
         {
             this.BaseAtom = baseAtom;
             this.DegreeAtom = degreeAtom;
         }
 
-        public Atom? BaseAtom { get; }
+        public Atom BaseAtom { get; }
 
         public Atom? DegreeAtom { get; }
 
@@ -39,7 +39,7 @@ protected override Box CreateBoxCore(TexEnvironment environment)
             clearance = defaultRuleThickness + Math.Abs(clearance) / 4;
 
             // Create box for base atom, in cramped style.
-            var baseBox = this.BaseAtom!.CreateBox(environment.GetCrampedStyle()); // Nullable TODO: See whether BaseAtom is really always non-null here
+            var baseBox = this.BaseAtom.CreateBox(environment.GetCrampedStyle());
 
             // Create box for radical sign.
             var totalHeight = baseBox.Height + baseBox.Depth;

src/WpfMath/Atoms/ScriptsAtom.cs

@@ -57,9 +57,9 @@ protected override Box CreateBoxCore(TexEnvironment environment)
             var delta = 0d;
             double shiftUp, shiftDown;
 
-            if (this.BaseAtom is AccentedAtom accentedAtom)
+            if (this.BaseAtom is AccentedAtom accentedAtom && accentedAtom.BaseAtom != null)
             {
-                var accentedBox = accentedAtom.BaseAtom!.CreateBox(environment.GetCrampedStyle());  // Nullable TODO: This probably needs null checking
+                var accentedBox = accentedAtom.BaseAtom.CreateBox(environment.GetCrampedStyle());
                 shiftUp = accentedBox.Height - texFont.GetSupDrop(superscriptStyle.Style);
                 shiftDown = accentedBox.Depth + texFont.GetSubDrop(subscriptStyle.Style);
             }
@@ -141,16 +141,21 @@ protected override Box CreateBoxCore(TexEnvironment environment)
             // Check if only superscript is set.
             if (subscriptBox == null)
             {
-                superscriptContainerBox!.Shift = -shiftUp; // Nullable TODO: Check whether superscriptContainerBox is really always non-null here
+                if (superscriptContainerBox == null)
+                    throw new Exception("ScriptsAtom with neither subscript nor superscript defined");
+
+                superscriptContainerBox.Shift = -shiftUp;
                 resultBox.Add(superscriptContainerBox);
                 return resultBox;
             }
 
             // Check if only subscript is set.
             if (superscriptBox == null)
             {
-                // Nullable TODO: Check whether subscriptContainerBox is really always non-null here
-                subscriptContainerBox!.Shift = Math.Max(Math.Max(shiftDown, texFont.GetSub1(style)), subscriptBox.Height - 4 *
+                if (subscriptContainerBox == null)
+                    throw new Exception("ScriptsAtom with neither subscript nor superscript defined");
+
+                subscriptContainerBox.Shift = Math.Max(Math.Max(shiftDown, texFont.GetSub1(style)), subscriptBox.Height - 4 *
                     Math.Abs(texFont.GetXHeight(style, lastFontId)) / 5);
                 resultBox.Add(subscriptContainerBox);
                 return resultBox;
@@ -178,11 +183,14 @@ protected override Box CreateBoxCore(TexEnvironment environment)
             scriptsInterSpace = shiftUp - superscriptBox.Depth + shiftDown - subscriptBox.Height;
 
             // Create box containing both superscript and subscript.
+            if (superscriptContainerBox == null || subscriptContainerBox == null)
+                throw new Exception($"ScriptsAtom with superscriptContainerBox = {superscriptContainerBox} and subscriptContainerBox = {subscriptContainerBox} is not supposed to be here");
+
             var scriptsBox = new VerticalBox();
-            superscriptContainerBox!.Shift = delta; // Nullable TODO: Check whether superscriptContainerBox is really always non-null here
+            superscriptContainerBox.Shift = delta;
             scriptsBox.Add(superscriptContainerBox);
             scriptsBox.Add(new StrutBox(0, scriptsInterSpace, 0, 0));
-            scriptsBox.Add(subscriptContainerBox!);
+            scriptsBox.Add(subscriptContainerBox);
             scriptsBox.Height = shiftUp + superscriptBox.Height;
             scriptsBox.Depth = shiftDown + subscriptBox.Depth;
             resultBox.Add(scriptsBox);

src/WpfMath/Atoms/SymbolAtom.cs

@@ -57,10 +57,13 @@ public static SymbolAtom GetAtom(string name, SourceSpan? source) =>
             TryGetAtom(name, source, out var atom) ? atom : throw new SymbolNotFoundException(name);
 
 #if !NET452
-        public static bool TryGetAtom(SourceSpan name, [NotNullWhen(true)] out SymbolAtom? atom) => TryGetAtom(name.ToString(), name, out atom);
+        public static bool TryGetAtom(SourceSpan name, [NotNullWhen(true)] out SymbolAtom? atom)
 #else
-        public static bool TryGetAtom(SourceSpan name, out SymbolAtom? atom) => TryGetAtom(name.ToString(), name, out atom);
+        public static bool TryGetAtom(SourceSpan name, out SymbolAtom? atom)
 #endif
+        {
+            return TryGetAtom(name.ToString(), name, out atom);
+        }
 
         public SymbolAtom(SourceSpan? source, SymbolAtom symbolAtom, TexAtomType type)
             : base(source, type)

src/WpfMath/DefaultTexFontParser.cs

@@ -50,7 +50,7 @@ private static void SetCharChildParsers()
 
         public DefaultTexFontParser()
         {
-            var doc = XDocument.Load(new System.IO.StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!)); // Nullable: CS8604: Possibly just throw if the resource is missing?
+            var doc = XDocument.Load(new System.IO.StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!));
             this.rootElement = doc.Root;
 
             this.parsedTextStyles = new Dictionary<string, CharFont[]>();

src/WpfMath/DelimiterFactory.cs

@@ -43,25 +43,28 @@ public static Box CreateBox(string symbol, double minHeight, TexEnvironment envi
                 if (extension.Bottom != null)
                     resultBox.Add(new CharBox(environment, extension.Bottom) { Source = source });
 
-                // Insert repeatable part multiple times until box is high enough.
-                var repeatBox = new CharBox(environment, extension.Repeat!) { Source = source }; // Nullable TODO: This probably needs null checking
-                do
+                if (extension.Repeat != null)
                 {
-                    if (extension.Top != null && extension.Bottom != null)
+                    // Insert repeatable part multiple times until box is high enough.
+                    var repeatBox = new CharBox(environment, extension.Repeat) { Source = source };
+                    do
                     {
-                        resultBox.Add(1, repeatBox);
-                        if (extension.Middle != null)
-                            resultBox.Add(resultBox.Children.Count - 1, repeatBox);
-                    }
-                    else if (extension.Bottom != null)
-                    {
-                        resultBox.Add(0, repeatBox);
-                    }
-                    else
-                    {
-                        resultBox.Add(repeatBox);
-                    }
-                } while (resultBox.Height + resultBox.Depth < minHeight);
+                        if (extension.Top != null && extension.Bottom != null)
+                        {
+                            resultBox.Add(1, repeatBox);
+                            if (extension.Middle != null)
+                                resultBox.Add(resultBox.Children.Count - 1, repeatBox);
+                        }
+                        else if (extension.Bottom != null)
+                        {
+                            resultBox.Add(0, repeatBox);
+                        }
+                        else
+                        {
+                            resultBox.Add(repeatBox);
+                        }
+                    } while (resultBox.Height + resultBox.Depth < minHeight);
+                }
 
                 return resultBox;
             }

src/WpfMath/GlueSettingsParser.cs

@@ -61,7 +61,7 @@ private static void SetStyleMappings()
 
         public GlueSettingsParser()
         {
-            var doc = XDocument.Load(new System.IO.StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!)); // Nullable: CS8604: Possibly just throw if the resource is missing?
+            var doc = XDocument.Load(new System.IO.StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!));
             this.rootElement = doc.Root;
 
             this.glueTypes = new List<Glue>();

src/WpfMath/Parsers/CommandParsers.cs

@@ -48,7 +48,7 @@ public CommandContext(
 
     internal class CommandProcessingResult
     {
-        /// <summary>A parsed atom. May be <c>null</c>.</summary>
+        /// <summary>A parsed atom..</summary>
         public Atom? Atom { get; }
 
         /// <summary>

src/WpfMath/PredefinedTexFormulaSettingsParser.cs

@@ -34,7 +34,7 @@ private static void AddToMap(IEnumerable<XElement> mapList, string[] table)
 
         public TexPredefinedFormulaSettingsParser()
         {
-            var doc = XDocument.Load(new System.IO.StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!)); // Nullable: CS8604: Possibly just throw if the resource is missing?
+            var doc = XDocument.Load(new System.IO.StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!));
             this.rootElement = doc.Root;
         }
 

src/WpfMath/TexFormulaHelper.cs

@@ -1,3 +1,4 @@
+using System.Diagnostics;
 using WpfMath.Atoms;
 
 namespace WpfMath
@@ -137,7 +138,8 @@ public void AddRadical(TexFormula baseFormula)
 
         public void AddRadical(TexFormula baseFormula, TexFormula? degreeFormula)
         {
-            this.Add(new Radical(null, baseFormula?.RootAtom, degreeFormula?.RootAtom));
+            Debug.Assert(baseFormula.RootAtom != null);
+            this.Add(new Radical(null, baseFormula.RootAtom, degreeFormula?.RootAtom));
         }
 
         public void AddOperator(string operatorFormula, string lowerLimitFormula, string upperLimitFormula)

src/WpfMath/TexFormulaParser.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
 using System.Windows;
@@ -43,9 +44,9 @@ public class TexFormulaParser
             "sqrt"
         };
 
-        private static IList<string> symbols = new List<string>(); // Nullable: CS8618
-        private static IList<string> delimeters = new List<string>();
-        private static HashSet<string> textStyles = new HashSet<string>();
+        private static readonly IList<string> symbols;
+        private static readonly IList<string> delimeters;
+        private static readonly HashSet<string> textStyles;
         private static readonly IDictionary<string, Func<SourceSpan, TexFormula?>> predefinedFormulas =
             new Dictionary<string, Func<SourceSpan, TexFormula?>>();
 
@@ -65,16 +66,6 @@ public class TexFormulaParser
         };
 
         static TexFormulaParser()
-        {
-            Initialize();
-        }
-
-        internal static string[][] DelimiterNames
-        {
-            get { return delimiterNames; }
-        }
-
-        private static void Initialize()
         {
             //
             // If start application isn't WPF, pack isn't registered by defaultTexFontParser
@@ -95,6 +86,11 @@ private static void Initialize()
             predefinedFormulasParser.Parse(predefinedFormulas);
         }
 
+        internal static string[][] DelimiterNames
+        {
+            get { return delimiterNames; }
+        }
+
         internal static string GetDelimeterMapping(char character)
         {
             try
@@ -535,6 +531,7 @@ private TexFormula ReadScript(
                             environment.CreateChildEnvironment());
 
                         source = value.Segment(start, position - start);
+                        Debug.Assert(sqrtFormula.RootAtom != null);
                         return new Tuple<AtomAppendMode, Atom?>(
                             AtomAppendMode.Add,
                             new Radical(source, sqrtFormula.RootAtom, degreeFormula?.RootAtom));
@@ -752,7 +749,7 @@ private Atom AttachScripts(
             var primesRowSource = new SourceSpan(
                 value.SourceName,
                 value.Source,
-                primesRowAtom.Source!.Start, // Nullable TODO: This might need null checking
+                primesRowAtom.Source!.Start,
                 position - primesRowAtom.Source.Start);
             primesRowAtom = primesRowAtom.WithSource(primesRowSource);
 
@@ -803,7 +800,7 @@ private Atom AttachScripts(
             var superscriptAtom = superscriptFormula?.RootAtom;
             if (atom.GetRightType() == TexAtomType.BigOperator)
             {
-                var source = value.Segment(atom.Source!.Start, position - atom.Source.Start); // Nullable TODO: This might need null checking
+                var source = value.Segment(atom.Source!.Start, position - atom.Source.Start);
                 if (atom is BigOperatorAtom typedAtom)
                 {
                     return new BigOperatorAtom(

src/WpfMath/TexPredefinedFormulaParser.cs

@@ -85,7 +85,7 @@ private static Type[] GetArgumentTypes(IEnumerable<XElement> args)
 
         public TexPredefinedFormulaParser()
         {
-            var doc = XDocument.Load(new StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!)); // Nullable: CS8604: Possibly just throw if the resource is missing?
+            var doc = XDocument.Load(new StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!));
             this.rootElement = doc.Root;
         }
 
@@ -141,7 +141,7 @@ public override void Parse(SourceSpan source, XElement element)
                 var argValues = GetArgumentValues(args);
 
                 var helper = new TexFormulaHelper(formula, source);
-                typeof(TexFormulaHelper).GetMethod(methodName, argTypes)!.Invoke(helper, argValues); // Nullable: Hard to verify here, I guess
+                typeof(TexFormulaHelper).GetMethod(methodName, argTypes)!.Invoke(helper, argValues);
             }
         }
 

src/WpfMath/TexSymbolParser.cs

@@ -38,7 +38,7 @@ private static void SetTypeMappings()
         public TexSymbolParser()
         {
             // for 3.5
-            var doc = XDocument.Load(new StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!)); // Nullable: CS8604: Possibly just throw if the resource is missing?
+            var doc = XDocument.Load(new StreamReader(Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)!));
             this.rootElement = doc.Root;
         }
 

src/WpfMath/Utils/Result.cs

@@ -30,6 +30,6 @@ public Result(TValue value, Exception? error)
 
         public Result<TProduct> Map<TProduct>(Func<TValue, TProduct> mapper) => this.IsSuccess
             ? Result.Ok(mapper(this.Value))
-            : Result.Error<TProduct>(this.Error!); // Nullable: CS8604, could be resolved by inlining IsSuccess
+            : Result.Error<TProduct>(this.Error!);
     }
 }