From 846871c495ec4a52057ebd214b1a2a59add61e2c Mon Sep 17 00:00:00 2001
From: Sam Rawlins <srawlins@google.com>
Date: Mon, 20 Sep 2021 15:43:33 -0700
Subject: [PATCH 1/3] Migrat mustachio to null safety

---
 lib/src/mustachio/annotations.dart           |  8 +-
 lib/src/mustachio/parser.dart                | 37 ++++----
 lib/src/mustachio/renderer_base.dart         | 87 +++++++++----------
 tool/mustachio/builder.dart                  | 42 ++++------
 tool/mustachio/codegen_aot_compiler.dart     | 43 +++++-----
 tool/mustachio/codegen_runtime_renderer.dart | 88 ++++++++++----------
 tool/mustachio/utilities.dart                |  2 -
 7 files changed, 145 insertions(+), 162 deletions(-)

diff --git a/lib/src/mustachio/annotations.dart b/lib/src/mustachio/annotations.dart
index e7854432ec..a0c57e8689 100644
--- a/lib/src/mustachio/annotations.dart
+++ b/lib/src/mustachio/annotations.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart=2.9
-
 // See the Mustachio README at tool/mustachio/README.md for high-level
 // documentation.
 
@@ -95,7 +93,7 @@ class RendererSpec {
 
   final String standardMdTemplate;
 
-  final Map<TemplateFormat, Uri> standardTemplateUris;
+  final Map<TemplateFormat, Uri?> standardTemplateUris;
 
   RendererSpec(
     this.name,
@@ -111,8 +109,8 @@ class RendererSpec {
   /// Parses a URI from a String which comes from a const annotation object.
   ///
   /// The String value may be the literal value, 'null'.
-  static Uri _parseUriFromAnnotation(String unparsed) =>
-      unparsed == 'null' || unparsed == null ? null : Uri.parse(unparsed);
+  static Uri? _parseUriFromAnnotation(String unparsed) =>
+      unparsed == 'null' ? null : Uri.parse(unparsed);
 
   ClassElement get contextElement => contextType.element;
 }
diff --git a/lib/src/mustachio/parser.dart b/lib/src/mustachio/parser.dart
index a33e3c10f7..fbd4136ef5 100644
--- a/lib/src/mustachio/parser.dart
+++ b/lib/src/mustachio/parser.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart=2.9
-
 // See the Mustachio README at tool/mustachio/README.md for high-level
 // documentation.
 
@@ -50,7 +48,7 @@ class MustachioParser {
   ///   [sectionKey], the end tag is treated as plain text, not a tag.
   /// * if [sectionKey] is null, the end tag is treated as plain text, not a
   ///   tag.
-  List<MustachioNode> _parseBlock({String /*?*/ sectionKey}) {
+  List<MustachioNode> _parseBlock({String? sectionKey}) {
     var children = <MustachioNode>[];
     var textStartIndex = _index;
     var textEndIndex = _index;
@@ -128,7 +126,7 @@ class MustachioParser {
             trimTextRight();
           }
           addTextNode(textStartIndex, textEndIndex);
-          children.add(result.node);
+          children.add(result.node!);
           textStartIndex = _index;
           continue;
         }
@@ -193,7 +191,7 @@ class MustachioParser {
   ///
   /// [_index] should be at the character immediately following the `>`
   /// character which opens a possible partial tag.
-  _TagParseResult _parsePartial({@required int tagStartIndex}) {
+  _TagParseResult _parsePartial({required int tagStartIndex}) {
     var startIndex = _index;
     int endIndex;
     while (true) {
@@ -229,7 +227,7 @@ class MustachioParser {
   /// [_index] should be at the character immediately following the `#`
   /// character which opens a possible section tag.
   _TagParseResult _parseSection(
-      {@required bool invert, @required int tagStartIndex}) {
+      {required bool invert, required int tagStartIndex}) {
     var parsedKey = _parseKey();
     if (parsedKey.type == _KeyParseResultType.notKey) {
       return _TagParseResult.notTag;
@@ -239,6 +237,7 @@ class MustachioParser {
 
     var children = _parseBlock(sectionKey: parsedKey.joinedNames);
     var span = _sourceFile.span(tagStartIndex, _index);
+    var parsedKeySpan = parsedKey.span!;
 
     if (parsedKey.names.length > 1) {
       // Desugar section with dots into nested sections.
@@ -252,7 +251,7 @@ class MustachioParser {
       // [three] section is the singular child node of the [two] section, and
       // the [two] section is the singular child of the [one] section.
       var lastName = parsedKey.names.last;
-      var keySpanEndOffset = parsedKey.span.end.offset;
+      var keySpanEndOffset = parsedKeySpan.end.offset;
       var lastNameSpan = _sourceFile.span(
           keySpanEndOffset - lastName.length, keySpanEndOffset);
       var section = Section([lastName], children,
@@ -262,7 +261,7 @@ class MustachioParser {
         // To find the start offset of the ith name, take the length of all of
         // the names 0 through `i - 1` re-joined with '.', and a final '.' at
         // the end.
-        var sectionKeyStartOffset = parsedKey.span.start.offset +
+        var sectionKeyStartOffset = parsedKeySpan.start.offset +
             (i == 0 ? 0 : parsedKey.names.take(i).join('.').length + 1);
         var keySpan = _sourceFile.span(
             sectionKeyStartOffset, sectionKeyStartOffset + sectionKey.length);
@@ -273,7 +272,7 @@ class MustachioParser {
     }
 
     return _TagParseResult.ok(Section(parsedKey.names, children,
-        invert: invert, span: span, keySpan: parsedKey.span));
+        invert: invert, span: span, keySpan: parsedKeySpan));
   }
 
   /// Tries to parse an end tag at [_index].
@@ -295,7 +294,7 @@ class MustachioParser {
   ///
   /// [_index] should be at the character immediately following the `{{`
   /// characters which open a possible variable tag.
-  _TagParseResult _parseVariable({@required int tagStartIndex}) {
+  _TagParseResult _parseVariable({required int tagStartIndex}) {
     var escape = true;
     if (_thisChar == $lbrace) {
       escape = false;
@@ -311,7 +310,7 @@ class MustachioParser {
 
     var span = _sourceFile.span(tagStartIndex, _index);
     return _TagParseResult.ok(Variable(parsedKey.names,
-        escape: escape, span: span, keySpan: parsedKey.span));
+        escape: escape, span: span, keySpan: parsedKey.span!));
   }
 
   /// Tries to parse a key at [_index].
@@ -436,7 +435,7 @@ class Text implements MustachioNode {
   @override
   final SourceSpan span;
 
-  Text(this.content, {@required this.span});
+  Text(this.content, {required this.span});
 
   @override
   String toString() => 'Text["$content"]';
@@ -457,7 +456,7 @@ class Variable with HasMultiNamedKey implements MustachioNode {
   final SourceSpan keySpan;
 
   Variable(this.key,
-      {@required this.escape, @required this.span, @required this.keySpan});
+      {required this.escape, required this.span, required this.keySpan});
 
   @override
   String toString() => 'Variable[$key, escape=$escape]';
@@ -481,7 +480,7 @@ class Section with HasMultiNamedKey implements MustachioNode {
   final SourceSpan keySpan;
 
   Section(this.key, this.children,
-      {@required this.invert, @required this.span, @required this.keySpan});
+      {required this.invert, required this.span, required this.keySpan});
 
   @override
   String toString() => 'Section[$key, invert=$invert]';
@@ -497,7 +496,7 @@ class Partial implements MustachioNode {
 
   final SourceSpan keySpan;
 
-  Partial(this.key, {@required this.span, @required this.keySpan});
+  Partial(this.key, {required this.span, required this.keySpan});
 }
 
 /// An enumeration of types of tag parse results.
@@ -519,10 +518,10 @@ class _TagParseResult {
   /// This field is `null` if EOF was reached, or if a tag was not parsed
   /// (perhaps it started out like a tag, but was malformed, and so is read as
   /// text).
-  final MustachioNode /*?*/ node;
+  final MustachioNode? node;
 
   /// The key of an end tag, if an end tag was parsed.
-  final String /*?*/ endTagKey;
+  final String? endTagKey;
 
   _TagParseResult(this.type, this.node, this.endTagKey);
 
@@ -564,12 +563,12 @@ class _KeyParseResult {
 
   /// The source span from where this key was parsed, if this represents a
   /// parsed key, othwerwise `null`.
-  final SourceSpan /*?*/ span;
+  final SourceSpan? span;
 
   const _KeyParseResult._(this.type, this.names, {this.span});
 
   factory _KeyParseResult(_KeyParseResultType type, String key,
-      {@required SourceSpan span}) {
+      {required SourceSpan span}) {
     if (key == '.') {
       return _KeyParseResult._(type, [key], span: span);
     } else {
diff --git a/lib/src/mustachio/renderer_base.dart b/lib/src/mustachio/renderer_base.dart
index 072594a264..77d1db8f69 100644
--- a/lib/src/mustachio/renderer_base.dart
+++ b/lib/src/mustachio/renderer_base.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart=2.9
-
 // See the Mustachio README at tool/mustachio/README.md for high-level
 // documentation.
 
@@ -48,9 +46,9 @@ class Template {
   final Map<File, Template> partialTemplates;
 
   Template._(
-      {@required this.ast,
-      @required this.partials,
-      @required this.partialTemplates});
+      {required this.ast,
+      required this.partials,
+      required this.partialTemplates});
 
   /// Parses [file] as a Mustache template, returning a [Template].
   ///
@@ -69,8 +67,8 @@ class Template {
   /// the directory containing `p1.html`, not relative to the top-level
   /// template), as `/foo/partials/p2.html`.
   static Future<Template> parse(File file,
-      {PartialResolver partialResolver,
-      @internal Map<File, Template> partialTemplates}) async {
+      {PartialResolver? partialResolver,
+      @internal Map<File, Template>? partialTemplates}) async {
     partialTemplates ??= <File, Template>{};
     if (partialResolver == null) {
       var pathContext = file.provider.pathContext;
@@ -113,7 +111,7 @@ class Template {
         if (!partials.containsKey(key)) {
           partials[key] = await partialResolver(key);
         }
-        var partialFile = partials[key];
+        var partialFile = partials[key]!;
         if (!partialTemplates.containsKey(partialFile)) {
           try {
             var partialTemplate = await Template.parse(partialFile,
@@ -139,7 +137,7 @@ abstract class RendererBase<T> {
   final T context;
 
   /// The renderer of the parent context, if any, otherwise `null`.
-  final RendererBase parent;
+  final RendererBase? parent;
 
   /// The current template being rendered.
   ///
@@ -165,12 +163,12 @@ abstract class RendererBase<T> {
   void write(String text) => sink.write(text);
 
   String get contextChainString =>
-      parent == null ? '$T' : '${parent.contextChainString} > $T';
+      parent == null ? '$T' : '${parent!.contextChainString} > $T';
 
   /// Returns the [Property] on this renderer named [name].
   ///
   /// If no property named [name] exists for this renderer, `null` is returned.
-  Property<T> getProperty(String key);
+  Property<T>? getProperty(String key);
 
   /// Resolves [names] into one or more field accesses, returning the result as
   /// a String.
@@ -186,8 +184,8 @@ abstract class RendererBase<T> {
     var firstName = names.first;
     try {
       var property = getProperty(firstName);
+      var remainingNames = [...names.skip(1)];
       if (property != null) {
-        var remainingNames = [...names.skip(1)];
         try {
           return property.renderVariable(context, property, remainingNames);
         } on PartialMustachioResolutionError catch (e) {
@@ -205,7 +203,7 @@ abstract class RendererBase<T> {
     }
 
     if (parent != null) {
-      return parent.getFields(node);
+      return parent!.getFields(node);
     } else {
       throw MustachioResolutionError(node.keySpan.message(
           "Failed to resolve '${names.first}' as a property on any types in the "
@@ -242,21 +240,22 @@ abstract class RendererBase<T> {
             "Failed to resolve '$key' as a property on any types in the "
             'current context'));
       } else {
-        return parent.section(node);
+        return parent!.section(node);
       }
     }
 
-    if (property.getBool != null) {
-      var boolResult = property.getBool(context);
+    var getBool = property.getBool;
+    if (getBool != null) {
+      var boolResult = getBool(context);
       if ((boolResult && !node.invert) || (!boolResult && node.invert)) {
         renderBlock(node.children);
       }
       return;
     }
 
-    if (property.renderIterable != null) {
-      var renderedIterable =
-          property.renderIterable(context, this, node.children, sink);
+    var renderIterable = property.renderIterable;
+    if (renderIterable != null) {
+      var renderedIterable = renderIterable(context, this, node.children, sink);
       if (node.invert && renderedIterable.isEmpty) {
         // An inverted section is rendered with the current context.
         renderBlock(node.children);
@@ -270,17 +269,18 @@ abstract class RendererBase<T> {
 
     // If this section is not a conditional or repeated section, it is a value
     // section, regardless of type.
-    if (node.invert && property.isNullValue(context)) {
+    var isNullValue = property.isNullValue!;
+    if (node.invert && isNullValue(context)) {
       renderBlock(node.children);
-    } else if (!node.invert && !property.isNullValue(context)) {
-      property.renderValue(context, this, node.children, sink);
+    } else if (!node.invert && !isNullValue(context)) {
+      property.renderValue!(context, this, node.children, sink);
     }
   }
 
   void partial(Partial node) {
     var key = node.key;
     var partialFile = template.partials[key];
-    var partialTemplate = template.partialTemplates[partialFile];
+    var partialTemplate = template.partialTemplates[partialFile]!;
     var outerTemplate = _template;
     _template = partialTemplate;
     renderBlock(partialTemplate.ast);
@@ -289,8 +289,13 @@ abstract class RendererBase<T> {
 }
 
 String renderSimple(
-    Object context, List<MustachioNode> ast, Template template, StringSink sink,
-    {@required RendererBase parent, Set<String> getters}) {
+  Object context,
+  List<MustachioNode> ast,
+  Template template,
+  StringSink sink, {
+  required RendererBase<Object> parent,
+  required Set<String> getters,
+}) {
   var renderer = SimpleRenderer(context, parent, template, sink, getters);
   renderer.renderBlock(ast);
   return renderer.sink.toString();
@@ -307,7 +312,7 @@ class SimpleRenderer extends RendererBase<Object> {
             invisibleGetters: invisibleGetters);
 
   @override
-  Property<Object> getProperty(String key) {
+  Property<Object>? getProperty(String key) {
     if (_invisibleGetters.contains(key)) {
       throw MustachioResolutionError(_failedKeyVisibilityMessage(key));
     } else {
@@ -324,7 +329,7 @@ class SimpleRenderer extends RendererBase<Object> {
     } else if (_invisibleGetters.contains(firstName)) {
       throw MustachioResolutionError(_failedKeyVisibilityMessage(firstName));
     } else if (parent != null) {
-      return parent.getFields(node);
+      return parent!.getFields(node);
     } else {
       return 'null';
     }
@@ -345,34 +350,32 @@ class SimpleRenderer extends RendererBase<Object> {
 @immutable
 class Property<T> {
   /// Gets the value of this property on the object [context].
-  final Object /*?*/ Function(T context) /*!*/ getValue;
+  final Object? Function(T context) getValue;
 
-  final String /*!*/ Function(
-      T, Property<T>, List<String> /*!*/) /*?*/ renderVariable;
+  final String Function(T, Property<T>, List<String>) renderVariable;
 
   /// Gets the bool value (true or false, never null) of this property on the
   /// object [context].
-  final bool /*!*/ Function(T context) /*?*/ getBool;
+  final bool Function(T context)? getBool;
 
-  final Iterable<void> /*!*/ Function(
-          T, RendererBase<T>, List<MustachioNode> /*!*/, StringSink /*!*/) /*?*/
-      renderIterable;
+  final Iterable<void> Function(
+      T, RendererBase<T>, List<MustachioNode>, StringSink)? renderIterable;
 
-  final bool /*!*/ Function(T) /*?*/ isNullValue;
+  final bool Function(T)? isNullValue;
 
-  final void /*!*/ Function(T, RendererBase<T>, List<MustachioNode> /*!*/,
-      StringSink /*!*/) /*?*/ renderValue;
+  final void Function(T, RendererBase<T>, List<MustachioNode>, StringSink)?
+      renderValue;
 
   Property(
-      {@required this.getValue,
-      this.renderVariable,
+      {required this.getValue,
+      required this.renderVariable,
       this.getBool,
       this.renderIterable,
       this.isNullValue,
       this.renderValue});
 
-  String /*!*/ renderSimpleVariable(
-      T c, List<String> /*!*/ remainingNames, String /*!*/ typeString) {
+  String renderSimpleVariable(
+      T c, List<String> remainingNames, String typeString) {
     if (remainingNames.isEmpty) {
       return getValue(c).toString();
     } else {
@@ -421,7 +424,7 @@ class _MustachioResolutionErrorWithoutSpan extends Error {
 extension MapExtensions<T> on Map<String, Property<T>> {
   Property<T> getValue(String name) {
     if (containsKey(name)) {
-      return this[name];
+      return this[name]!;
     } else {
       throw PartialMustachioResolutionError(name, T);
     }
diff --git a/tool/mustachio/builder.dart b/tool/mustachio/builder.dart
index 17a39abae1..9d98ce3c89 100644
--- a/tool/mustachio/builder.dart
+++ b/tool/mustachio/builder.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart=2.9
-
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/member.dart';
@@ -37,7 +35,6 @@ class MustachioBuilder implements Builder {
     var inputId = buildStep.inputId;
 
     final entryLib = await buildStep.inputLibrary;
-    if (entryLib == null) return;
 
     final rendererGatherer = _RendererGatherer(entryLib);
 
@@ -53,8 +50,8 @@ class MustachioBuilder implements Builder {
 
     if (rendererGatherer._rendererSpecs.isEmpty) {
       await buildStep.writeAsString(runtimeRenderersLibrary, '');
-      await buildStep.writeAsString(aotLibraries[TemplateFormat.html], '');
-      await buildStep.writeAsString(aotLibraries[TemplateFormat.md], '');
+      await buildStep.writeAsString(aotLibraries[TemplateFormat.html]!, '');
+      await buildStep.writeAsString(aotLibraries[TemplateFormat.md]!, '');
 
       return;
     }
@@ -85,7 +82,8 @@ class MustachioBuilder implements Builder {
         aotRenderersContents = '';
       }
 
-      await buildStep.writeAsString(aotLibraries[format], aotRenderersContents);
+      await buildStep.writeAsString(
+          aotLibraries[format]!, aotRenderersContents);
     }
   }
 }
@@ -100,37 +98,33 @@ class _RendererGatherer {
 
     void addRendererSpecs(List<ElementAnnotation> annotations) {
       for (var annotation in annotations) {
-        if (annotation == null) continue;
+        //if (annotation == null) continue;
         if (annotation.element is ConstructorElement) {
-          if (annotation.element.enclosingElement.name == 'Renderer') {
+          if (annotation.element!.enclosingElement!.name == 'Renderer') {
             rendererSpecs.add(_buildRendererSpec(annotation));
           }
         } else if (annotation.element is ConstructorMember) {
-          if (annotation.element.enclosingElement.name == 'Renderer') {
+          if (annotation.element!.enclosingElement!.name == 'Renderer') {
             rendererSpecs.add(_buildRendererSpec(annotation));
           }
         }
       }
     }
 
-    if (entryLib.metadata != null) {
-      addRendererSpecs(entryLib.metadata);
-    }
+    addRendererSpecs(entryLib.metadata);
     for (final element in entryLib.topLevelElements) {
-      if (element.metadata != null) {
-        addRendererSpecs(element.metadata);
-      }
+      addRendererSpecs(element.metadata);
     }
     return _RendererGatherer._(rendererSpecs);
   }
 
   static RendererSpec _buildRendererSpec(ElementAnnotation annotation) {
-    var constantValue = annotation.computeConstantValue();
-    var nameField = constantValue.getField('name');
+    var constantValue = annotation.computeConstantValue()!;
+    var nameField = constantValue.getField('name')!;
     if (nameField.isNull) {
       throw StateError('@Renderer name must not be null');
     }
-    var contextField = constantValue.getField('context');
+    var contextField = constantValue.getField('context')!;
     if (contextField.isNull) {
       throw StateError('@Renderer context must not be null');
     }
@@ -138,12 +132,12 @@ class _RendererGatherer {
     assert(contextFieldType.typeArguments.length == 1);
     var contextType = contextFieldType.typeArguments.single;
 
-    var visibleTypesField = constantValue.getField('visibleTypes');
+    var visibleTypesField = constantValue.getField('visibleTypes')!;
     if (visibleTypesField.isNull) {
       throw StateError('@Renderer visibleTypes must not be null');
     }
     var visibleTypes = {
-      ...visibleTypesField.toSetValue().map((object) => object.toTypeValue())
+      ...visibleTypesField.toSetValue()!.map((object) => object.toTypeValue()!)
     };
 
     var standardHtmlTemplateField =
@@ -151,11 +145,11 @@ class _RendererGatherer {
     var standardMdTemplateField = constantValue.getField('standardMdTemplate');
 
     return RendererSpec(
-      nameField.toSymbolValue(),
-      contextType,
+      nameField.toSymbolValue()!,
+      contextType as InterfaceType,
       visibleTypes,
-      standardHtmlTemplateField.toStringValue(),
-      standardMdTemplateField.toStringValue(),
+      standardHtmlTemplateField!.toStringValue()!,
+      standardMdTemplateField!.toStringValue()!,
     );
   }
 }
diff --git a/tool/mustachio/codegen_aot_compiler.dart b/tool/mustachio/codegen_aot_compiler.dart
index 1e12843d15..0d25e9b2cb 100644
--- a/tool/mustachio/codegen_aot_compiler.dart
+++ b/tool/mustachio/codegen_aot_compiler.dart
@@ -2,14 +2,13 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart=2.9
-
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/dart/element/type_provider.dart';
 import 'package:analyzer/dart/element/type_system.dart';
 import 'package:build/build.dart';
 import 'package:code_builder/code_builder.dart';
+import 'package:collection/collection.dart';
 import 'package:dart_style/dart_style.dart';
 import 'package:dartdoc/src/mustachio/annotations.dart';
 import 'package:dartdoc/src/mustachio/parser.dart';
@@ -118,7 +117,7 @@ class _AotCompiler {
     String rendererName,
     AssetId templateAssetId,
     _BuildData buildData, {
-    List<_VariableLookup> contextStack,
+    List<_VariableLookup> contextStack = const [],
   }) async {
     var template = await buildData._buildStep.readAsString(templateAssetId);
     var syntaxTree = MustachioParser(template, templateAssetId.uri).parse();
@@ -133,9 +132,9 @@ class _AotCompiler {
     this._templateAssetId,
     this._syntaxTree,
     this._buildData, {
-    List<_VariableLookup> contextStack,
-  })  : _contextStack = _rename(contextStack ?? []),
-        _contextNameCounter = contextStack?.length ?? 0;
+    required List<_VariableLookup> contextStack,
+  })  : _contextStack = _rename(contextStack),
+        _contextNameCounter = contextStack.length;
 
   /// Returns a copy of [original], replacing each variable's name with
   /// `context0` through `contextN` for `N` variables.
@@ -172,15 +171,16 @@ class _AotCompiler {
     var typeParameters = <TypeReference>[];
     for (var context in _contextStack) {
       for (var typeParameter in context.type.element.typeParameters) {
-        if (typeParameter.bound == null) {
+        var bound = typeParameter.bound;
+        if (bound == null) {
           typeParameters
               .add(TypeReference((b) => b..symbol = typeParameter.name));
         } else {
-          var bound = typeParameter.bound.element;
-          var boundUri = await _elementUri(bound);
+          var boundElement = bound.element!;
+          var boundUri = await _elementUri(boundElement);
           typeParameters.add(TypeReference((b) => b
             ..symbol = typeParameter.name
-            ..bound = refer(bound.name, boundUri)));
+            ..bound = refer(boundElement.name!, boundUri)));
         }
       }
     }
@@ -222,12 +222,13 @@ return buffer.toString();
 
   /// Returns the URI of [element] for use in generated import directives.
   Future<String> _elementUri(Element element) async {
-    if (element.library.isInSdk) {
-      return element.library.source.uri.toString();
+    var libraryElement = element.library!;
+    if (libraryElement.isInSdk) {
+      return libraryElement.source.uri.toString();
     }
 
     var typeAssetId =
-        await _buildData._buildStep.resolver.assetIdForElement(element.library);
+        await _buildData._buildStep.resolver.assetIdForElement(libraryElement);
     if (typeAssetId.path.startsWith('lib/')) {
       return typeAssetId.uri.toString();
     } else {
@@ -298,9 +299,8 @@ class _BlockCompiler {
     path.add('_$fileName.$extension');
     var partialAssetId = AssetId.resolve(Uri.parse(path.join('/')),
         from: _templateCompiler._templateAssetId);
-    var partialRenderer = _templateCompiler._partialCompilers.firstWhere(
-        (p) => p._templateAssetId == partialAssetId,
-        orElse: () => null);
+    var partialRenderer = _templateCompiler._partialCompilers
+        .firstWhereOrNull((p) => p._templateAssetId == partialAssetId);
     if (partialRenderer == null) {
       var sanitizedKey = node.key.replaceAll('.', '_').replaceAll('/', '_');
       var name = '${partialBaseName}_'
@@ -324,11 +324,6 @@ class _BlockCompiler {
   /// Compiles [node] into a renderer's Dart source.
   Future<void> _compileSection(Section node) async {
     var variableLookup = _lookUpGetter(node);
-    if (variableLookup == null) {
-      throw MustachioResolutionError(node.keySpan.message(
-          "Failed to resolve '${node.key}' as a property on the context type:"
-          '$contextType'));
-    }
     if (variableLookup.type.isDartCoreBool) {
       // Conditional block.
       await _compileConditionalSection(variableLookup, node.children,
@@ -382,8 +377,8 @@ class _BlockCompiler {
       // determine that the inner type of the loop is, for example,
       // `Future<int>`.
       var iterableElement = typeProvider.iterableElement;
-      var iterableType = variableLookup.type.asInstanceOf(iterableElement);
-      var innerContextType = iterableType.typeArguments.first;
+      var iterableType = variableLookup.type.asInstanceOf(iterableElement)!;
+      var innerContextType = iterableType.typeArguments.first as InterfaceType;
       var innerContext = _VariableLookup(innerContextType, newContextName);
       _contextStack.push(innerContext);
       await _compile(block);
@@ -449,7 +444,7 @@ class _BlockCompiler {
         type = getter.returnType;
         contextChain = '$contextChain.$secondaryKey';
       }
-      return _VariableLookup(type, contextChain);
+      return _VariableLookup(type as InterfaceType, contextChain);
     }
 
     var contextTypes = [
diff --git a/tool/mustachio/codegen_runtime_renderer.dart b/tool/mustachio/codegen_runtime_renderer.dart
index 162c6a99b6..7ffd943833 100644
--- a/tool/mustachio/codegen_runtime_renderer.dart
+++ b/tool/mustachio/codegen_runtime_renderer.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart=2.9
-
 import 'dart:collection';
 
 import 'package:analyzer/dart/element/element.dart';
@@ -12,7 +10,6 @@ import 'package:analyzer/dart/element/type_provider.dart';
 import 'package:analyzer/dart/element/type_system.dart';
 import 'package:dart_style/dart_style.dart';
 import 'package:dartdoc/src/mustachio/annotations.dart';
-import 'package:meta/meta.dart';
 import 'package:path/path.dart' as p;
 
 import 'utilities.dart';
@@ -24,7 +21,7 @@ String buildRuntimeRenderers(Set<RendererSpec> specs, Uri sourceUri,
   var visibleElements = specs
       .map((spec) => spec.visibleTypes)
       .reduce((value, element) => value.union(element))
-      .map((type) => type.element)
+      .map((type) => type.element!)
       .toSet();
   var raw = RuntimeRenderersBuilder(
           sourceUri, typeProvider, typeSystem, visibleElements,
@@ -189,11 +186,11 @@ import '${p.basename(_sourceUri.path)}';
   /// * If [type] is an [InterfaceType] (not assignable to [Iterable]), returns
   ///   [type].
   /// * Otherwise, returns `null`, indicating there is no relevant type.
-  InterfaceType _relevantTypeFrom(DartType type) {
+  InterfaceType? _relevantTypeFrom(DartType type) {
     if (type is InterfaceType) {
       if (_typeSystem.isAssignableTo(type, _typeProvider.iterableDynamicType)) {
         var iterableElement = _typeProvider.iterableElement;
-        var iterableType = type.asInstanceOf(iterableElement);
+        var iterableType = type.asInstanceOf(iterableElement)!;
         var innerType = iterableType.typeArguments.first;
 
         return _relevantTypeFrom(innerType);
@@ -202,7 +199,7 @@ import '${p.basename(_sourceUri.path)}';
       }
     } else if (type is TypeParameterType) {
       var bound = type.bound;
-      if (bound == null || bound.isDynamic) {
+      if (bound.isDynamic) {
         // Don't add functions for a generic type, for example
         // `List<E>.first` has type `E`, which we don't have a specific
         // renderer for.
@@ -225,9 +222,9 @@ import '${p.basename(_sourceUri.path)}';
   /// * superclass constraints (if [type] a mixin),
   /// * types of relevant properties (recursively).
   void _addTypeHierarchyToProcess(
-    InterfaceType type, {
-    @required bool isFullRenderer,
-    @required bool includeRenderFunction,
+    InterfaceType? type, {
+    required bool isFullRenderer,
+    required bool includeRenderFunction,
   }) {
     while (type != null) {
       _addTypeToProcess(
@@ -269,8 +266,8 @@ import '${p.basename(_sourceUri.path)}';
   /// Adds [type] to the [_typesToProcess] queue, if it is not already there.
   void _addTypeToProcess(
     ClassElement element, {
-    @required bool isFullRenderer,
-    @required bool includeRenderFunction,
+    required bool isFullRenderer,
+    required bool includeRenderFunction,
   }) {
     var types = _typesToProcess.where((rs) => rs._contextClass == element);
     if (types.isEmpty) {
@@ -316,10 +313,11 @@ import '${p.basename(_sourceUri.path)}';
     if (_allVisibleElements.contains(element)) {
       return true;
     }
-    if (element.supertype == null) {
+    var supertype = element.supertype;
+    if (supertype == null) {
       return false;
     }
-    return _isVisibleToMustache(element.supertype.element);
+    return _isVisibleToMustache(supertype.element);
   }
 
   /// Builds render functions and the renderer class for [renderer].
@@ -334,7 +332,7 @@ import '${p.basename(_sourceUri.path)}';
   /// renderer classes are not built, having been built for a different
   /// [_RendererInfo].
   void _buildRenderer(_RendererInfo renderer,
-      {@required bool buildOnlyPublicFunction}) {
+      {required bool buildOnlyPublicFunction}) {
     var typeName = renderer._typeName;
     var typeWithVariables = '$typeName${renderer._typeVariablesString}';
 
@@ -413,37 +411,35 @@ class ${renderer._rendererClassName}${renderer._typeParametersString}
     static final Map<Type, Object> _propertyMapCache = {};
     static Map<String, Property<$_contextTypeVariable>> propertyMap$generics() =>
         _propertyMapCache.putIfAbsent($_contextTypeVariable, () => {''');
-    if (contextClass.supertype != null) {
-      var superclassRendererName =
-          _typeToRendererClassName[contextClass.supertype.element];
+    var supertype = contextClass.supertype;
+    if (supertype != null) {
+      var superclassRendererName = _typeToRendererClassName[supertype.element];
       if (superclassRendererName != null) {
         var superMapName = '$superclassRendererName.propertyMap';
         var generics = asGenerics([
-          ...contextClass.supertype.typeArguments
+          ...supertype.typeArguments
               .map((e) => e.getDisplayString(withNullability: false)),
           _contextTypeVariable
         ]);
         _buffer.writeln('    ...$superMapName$generics(),');
       }
     }
-    if (contextClass.mixins != null) {
-      // Mixins are spread into the property map _after_ the super class, so
-      // that they override any values which need to be overridden. Superclass
-      // and mixins override from left to right, as do spreads:
-      // `class C extends E with M, N` first takes members from N, then M, then
-      // E. Similarly, `{...a, ...b, ...c}` will feature elements from `c` which
-      // override `b` and `a`.
-      for (var mixin in contextClass.mixins) {
-        var mixinRendererName = _typeToRendererClassName[mixin.element];
-        if (mixinRendererName != null) {
-          var mixinMapName = '$mixinRendererName.propertyMap';
-          var generics = asGenerics([
-            ...mixin.typeArguments
-                .map((e) => e.getDisplayString(withNullability: false)),
-            _contextTypeVariable
-          ]);
-          _buffer.writeln('    ...$mixinMapName$generics(),');
-        }
+    // Mixins are spread into the property map _after_ the super class, so
+    // that they override any values which need to be overridden. Superclass
+    // and mixins override from left to right, as do spreads:
+    // `class C extends E with M, N` first takes members from N, then M, then
+    // E. Similarly, `{...a, ...b, ...c}` will feature elements from `c` which
+    // override `b` and `a`.
+    for (var mixin in contextClass.mixins) {
+      var mixinRendererName = _typeToRendererClassName[mixin.element];
+      if (mixinRendererName != null) {
+        var mixinMapName = '$mixinRendererName.propertyMap';
+        var generics = asGenerics([
+          ...mixin.typeArguments
+              .map((e) => e.getDisplayString(withNullability: false)),
+          _contextTypeVariable
+        ]);
+        _buffer.writeln('    ...$mixinMapName$generics(),');
       }
     }
     for (var property in [...contextClass.accessors]
@@ -452,9 +448,9 @@ class ${renderer._rendererClassName}${renderer._typeParametersString}
       if (returnType is InterfaceType) {
         _writeProperty(renderer, property, returnType);
       } else if (returnType is TypeParameterType &&
-          returnType.bound != null &&
+          //returnType.bound != null &&
           !returnType.bound.isDynamic) {
-        _writeProperty(renderer, property, returnType.bound);
+        _writeProperty(renderer, property, returnType.bound as InterfaceType);
       }
     }
     _buffer.writeln('});');
@@ -523,7 +519,7 @@ renderVariable:
           var renderFunctionName = _typeToRenderFunctionName[innerType.element];
           String renderCall;
           if (renderFunctionName == null) {
-            var typeName = innerType.element.name;
+            var typeName = innerType.element!.name!;
             if (innerType is InterfaceType) {
               _invisibleGetters.putIfAbsent(
                   typeName, () => innerType.element.allAccessorNames);
@@ -585,7 +581,7 @@ renderValue:
     _buffer.write('const _invisibleGetters = {');
     for (var class_ in _invisibleGetters.keys.toList()..sort()) {
       _buffer.write("'$class_':");
-      var getters = _invisibleGetters[class_];
+      var getters = _invisibleGetters[class_]!;
       _buffer.write('{${getters.map((e) => "'$e'").join(', ')}},');
     }
     _buffer.write('};');
@@ -620,14 +616,14 @@ class _RendererInfo {
   bool includeRenderFunction;
 
   /// The public API function name specified with @Renderer, or null.
-  String publicApiFunctionName;
+  String? publicApiFunctionName;
 
   factory _RendererInfo(
     ClassElement contextClass, {
     bool public = false,
     bool isFullRenderer = true,
     bool includeRenderFunction = true,
-    String publicApiFunctionName,
+    String? publicApiFunctionName,
   }) {
     var typeBaseName = contextClass.name;
     var renderFunctionName = '_render_$typeBaseName';
@@ -648,8 +644,8 @@ class _RendererInfo {
     this._contextClass,
     this._renderFunctionName,
     this._rendererClassName, {
-    @required this.isFullRenderer,
-    @required this.includeRenderFunction,
+    required this.isFullRenderer,
+    required this.includeRenderFunction,
     this.publicApiFunctionName,
   });
 
@@ -679,7 +675,7 @@ extension on ClassElement {
   /// Returns a set of the names of all accessors on this [ClassElement], including supertypes.
   Set<String> get allAccessorNames {
     return {
-      ...?supertype?.element?.allAccessorNames,
+      ...?supertype?.element.allAccessorNames,
       ...accessors
           .where((e) => e.isPublic && !e.isStatic && !e.isSetter)
           .map((e) => e.name),
diff --git a/tool/mustachio/utilities.dart b/tool/mustachio/utilities.dart
index 920a6592b3..983c421a5e 100644
--- a/tool/mustachio/utilities.dart
+++ b/tool/mustachio/utilities.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart=2.9
-
 import 'package:analyzer/dart/element/element.dart';
 
 extension ClassExtensions on ClassElement {

From a81cf8242c6a2e7c2866b0c122bed0ee5daf963b Mon Sep 17 00:00:00 2001
From: Sam Rawlins <srawlins@google.com>
Date: Mon, 20 Sep 2021 16:36:44 -0700
Subject: [PATCH 2/3] Comments

---
 tool/mustachio/builder.dart                  | 1 -
 tool/mustachio/codegen_runtime_renderer.dart | 1 -
 2 files changed, 2 deletions(-)

diff --git a/tool/mustachio/builder.dart b/tool/mustachio/builder.dart
index 9d98ce3c89..e7fd0a509e 100644
--- a/tool/mustachio/builder.dart
+++ b/tool/mustachio/builder.dart
@@ -98,7 +98,6 @@ class _RendererGatherer {
 
     void addRendererSpecs(List<ElementAnnotation> annotations) {
       for (var annotation in annotations) {
-        //if (annotation == null) continue;
         if (annotation.element is ConstructorElement) {
           if (annotation.element!.enclosingElement!.name == 'Renderer') {
             rendererSpecs.add(_buildRendererSpec(annotation));
diff --git a/tool/mustachio/codegen_runtime_renderer.dart b/tool/mustachio/codegen_runtime_renderer.dart
index 7ffd943833..0fe0b4cfd5 100644
--- a/tool/mustachio/codegen_runtime_renderer.dart
+++ b/tool/mustachio/codegen_runtime_renderer.dart
@@ -448,7 +448,6 @@ class ${renderer._rendererClassName}${renderer._typeParametersString}
       if (returnType is InterfaceType) {
         _writeProperty(renderer, property, returnType);
       } else if (returnType is TypeParameterType &&
-          //returnType.bound != null &&
           !returnType.bound.isDynamic) {
         _writeProperty(renderer, property, returnType.bound as InterfaceType);
       }

From 6d7ee73ac531228953de63a391ddb4696f1998f2 Mon Sep 17 00:00:00 2001
From: Sam Rawlins <srawlins@google.com>
Date: Tue, 21 Sep 2021 19:14:47 -0700
Subject: [PATCH 3/3] cool-fix

---
 tool/mustachio/codegen_runtime_renderer.dart | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tool/mustachio/codegen_runtime_renderer.dart b/tool/mustachio/codegen_runtime_renderer.dart
index 0fe0b4cfd5..ef7b526c7b 100644
--- a/tool/mustachio/codegen_runtime_renderer.dart
+++ b/tool/mustachio/codegen_runtime_renderer.dart
@@ -549,10 +549,8 @@ renderIterable:
         String renderCall;
         if (renderFunctionName == null) {
           var typeName = getterType.element.name;
-          if (getterType is InterfaceType) {
-            _invisibleGetters.putIfAbsent(
-                typeName, () => getterType.element.allAccessorNames);
-          }
+          _invisibleGetters.putIfAbsent(
+              typeName, () => getterType.element.allAccessorNames);
           renderCall =
               'renderSimple(c.$getterName, ast, r.template, sink, parent: r, '
               "getters: _invisibleGetters['$typeName'])";