DAS: Rearrange code to promote variables better

The motivation here was to remove the local duplicate variables like
`final_foo` or `foo_final`. These variables only existed because the
variables they duplicate lose their promoted types inside the
`builder.addDartFileEdit` closure. They lose their promoted type
because they are multiply assigned in loops or not always promoted to
be non-null.

Often the fix is to replace a `if (x == null) return` with
`} else { return; }`. I think this code more directly represents the
flow of code, rather than relying on the nullity of a variable, like
"is this variable still null? Oh then we must not have entered any
of the situations above, so we should return."

Change-Id: I9dd6686b7f4d9c6caf59c171179b129a5a957ba8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/418160
Reviewed-by: Phil Quitslund <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>

Author: srawlins

pkg/analysis_server/lib/src/services/correction/dart/add_async.dart

@@ -39,27 +39,27 @@ class AddAsync extends ResolvedCorrectionProducer {
     switch (_type) {
       case _Type.missingReturn:
         var node = this.node;
-        FunctionBody? body;
-        DartType? returnType;
+        FunctionBody body;
+        DartType returnType;
         switch (node) {
           case FunctionDeclaration():
             body = node.functionExpression.body;
             if (node.declaredFragment?.element case var declaredElement?) {
               returnType = declaredElement.returnType;
             } else if (node.declaredFragment case var declaredFragment?) {
               returnType = declaredFragment.element.returnType;
+            } else {
+              return;
             }
           case MethodDeclaration():
             body = node.body;
             returnType = node.declaredFragment!.element.returnType;
-        }
-        if (body == null || returnType == null) {
-          return;
+          default:
+            return;
         }
         if (_isFutureVoid(returnType) && _hasNoReturns(body)) {
-          var final_body = body;
           await builder.addDartFileEdit(file, (builder) {
-            builder.addSimpleInsertion(final_body.offset, 'async ');
+            builder.addSimpleInsertion(body.offset, 'async ');
           });
         }
       case _Type.wrongReturnType:

pkg/analysis_server/lib/src/services/correction/dart/add_missing_enum_case_clauses.dart

@@ -83,7 +83,7 @@ class AddMissingEnumCaseClauses extends ResolvedCorrectionProducer {
     var singleIndent = utils.oneIndent;
 
     var prefixString = prefix.isNotEmpty ? '$prefix.' : '';
-    var enumName_final = '$prefixString$enumName';
+    var prefixedEnumName = '$prefixString$enumName';
     await builder.addDartFileEdit(file, (builder) {
       builder.insertCaseClauseAtEnd(
         switchKeyword: statement.switchKeyword,
@@ -110,7 +110,7 @@ class AddMissingEnumCaseClauses extends ResolvedCorrectionProducer {
           // TODO(brianwilkerson): Consider inserting the names in order into the
           //  switch statement.
           for (var constantName in unhandledEnumCases) {
-            addMissingCase('$enumName_final.$constantName');
+            addMissingCase('$prefixedEnumName.$constantName');
           }
           if (unhandledNullValue) {
             addMissingCase('null');

pkg/analysis_server/lib/src/services/correction/dart/change_to_static_access.dart

@@ -28,36 +28,40 @@ class ChangeToStaticAccess extends ResolvedCorrectionProducer {
 
   @override
   Future<void> compute(ChangeBuilder builder) async {
-    Expression? target;
-    Element2? invokedElement;
     var identifier = node;
-    if (identifier is SimpleIdentifier) {
-      var parent = identifier.parent;
-      if (parent is MethodInvocation) {
-        if (parent.methodName == identifier) {
-          target = parent.target;
-          invokedElement = identifier.element;
-        }
-      } else if (parent is PrefixedIdentifier) {
-        if (parent.identifier == identifier) {
-          target = parent.prefix;
-          invokedElement = identifier.element;
-        }
+    if (identifier is! SimpleIdentifier) {
+      return;
+    }
+
+    Expression target;
+    var parent = identifier.parent;
+    if (parent case MethodInvocation(target: var parentTarget?)) {
+      if (parent.methodName != identifier) {
+        return;
       }
+      target = parentTarget;
+    } else if (parent is PrefixedIdentifier) {
+      if (parent.identifier != identifier) {
+        return;
+      }
+      target = parent.prefix;
+    } else {
+      return;
     }
-    if (target == null || invokedElement is! ExecutableElement2) {
+
+    var invokedElement = identifier.element;
+    if (invokedElement is! ExecutableElement2) {
       return;
     }
 
-    var target_final = target;
     var declaringElement = invokedElement.enclosingElement2;
 
     if (declaringElement is InterfaceElement2) {
       var declaringElementName = declaringElement.name3;
       if (declaringElementName != null) {
         _className = declaringElementName;
         await builder.addDartFileEdit(file, (builder) {
-          builder.addReplacement(range.node(target_final), (builder) {
+          builder.addReplacement(range.node(target), (builder) {
             builder.writeReference(declaringElement);
           });
         });
@@ -67,7 +71,7 @@ class ChangeToStaticAccess extends ResolvedCorrectionProducer {
       if (extensionName != null) {
         _className = extensionName;
         await builder.addDartFileEdit(file, (builder) {
-          builder.addReplacement(range.node(target_final), (builder) {
+          builder.addReplacement(range.node(target), (builder) {
             builder.writeReference(declaringElement);
           });
         });

pkg/analysis_server/lib/src/services/correction/dart/convert_to_expression_function_body.dart

@@ -50,11 +50,11 @@ class ConvertToExpressionFunctionBody extends ResolvedCorrectionProducer {
     if (statements.length != 1) {
       return;
     }
-    var onlyStatement = statements.first;
-    // prepare returned expression
-    Expression? returnExpression;
-    if (onlyStatement is ReturnStatement) {
-      returnExpression = onlyStatement.expression;
+    var onlyStatement = statements.single;
+    // Prepare the returned expression.
+    Expression returnExpression;
+    if (onlyStatement case ReturnStatement(:var expression?)) {
+      returnExpression = expression;
       if (onlyStatement.returnKeyword.precedingComments != null) {
         // TODO(srawlins): Include comments in fixed output.
         // https://github.com/dart-lang/sdk/issues/29313
@@ -82,25 +82,23 @@ class ConvertToExpressionFunctionBody extends ResolvedCorrectionProducer {
         // https://github.com/dart-lang/sdk/issues/29313
         return;
       }
-    }
-    if (returnExpression == null) {
+    } else {
       return;
     }
 
-    // Return expressions can be quite large, e.g. Flutter build() methods.
+    // Return expressions can be quite large, e.g. Flutter `build()` methods.
     // It is surprising to see this Quick Assist deep in the function body.
     if (selectionOffset >= returnExpression.offset) {
       return;
     }
 
-    var returnExpression_final = returnExpression;
     await builder.addDartFileEdit(file, (builder) {
       builder.addReplacement(range.node(body), (builder) {
         if (body.isAsynchronous) {
           builder.write('async ');
         }
         builder.write('=> ');
-        builder.write(utils.getNodeText(returnExpression_final));
+        builder.write(utils.getNodeText(returnExpression));
         var parent = body.parent;
         if (parent is! FunctionExpression ||
             parent.parent is FunctionDeclaration) {

pkg/analysis_server/lib/src/services/correction/dart/convert_to_relative_import.dart

@@ -74,10 +74,10 @@ class ConvertToRelativeImport extends ResolvedCorrectionProducer {
       from: path.dirname(sourceUri.path),
     );
 
-    var node_final = targetNode;
+    var uriNode = targetNode.uri;
     await builder.addDartFileEdit(file, (builder) {
       builder.addSimpleReplacement(
-        range.node(node_final.uri).getExpanded(-1),
+        range.node(uriNode).getExpanded(-1),
         relativePath,
       );
     });

pkg/analysis_server/lib/src/services/correction/dart/remove_unused_parameter.dart

@@ -25,23 +25,20 @@ class RemoveUnusedParameter extends ResolvedCorrectionProducer {
 
   @override
   Future<void> compute(ChangeBuilder builder) async {
-    // To work for the unused_parameter hint as well as the lint, we must
-    // allow for passing in `SimpleIdentifier`s.
+    // To work for the unused_element_parameter warning as well as the lint (?),
+    // we must allow for passing in `SimpleIdentifier`s.
     var maybeParameter = node;
     var maybeParameterParent = maybeParameter.parent;
     if (maybeParameter is SimpleIdentifier && maybeParameterParent != null) {
       maybeParameter = maybeParameterParent;
     }
 
-    var parameter = maybeParameter;
-    if (parameter is! FormalParameter) {
+    if (maybeParameter is! FormalParameter) {
       return;
     }
 
-    var parent = parameter.parent;
-    if (parent is DefaultFormalParameter) {
-      parameter = parent;
-    }
+    var parent = maybeParameter.parent;
+    var parameter = parent is DefaultFormalParameter ? parent : maybeParameter;
 
     var parameterList = parameter.parent;
     if (parameterList is! FormalParameterList) {
@@ -50,7 +47,6 @@ class RemoveUnusedParameter extends ResolvedCorrectionProducer {
 
     var parameters = parameterList.parameters;
     var index = parameters.indexOf(parameter);
-    var parameter_final = parameter;
     await builder.addDartFileEdit(file, (builder) {
       if (index == 0) {
         // Remove the first parameter in the list.
@@ -65,7 +61,7 @@ class RemoveUnusedParameter extends ResolvedCorrectionProducer {
           );
         } else {
           var following = parameters[1];
-          if (parameter_final.isRequiredPositional &&
+          if (parameter.isRequiredPositional &&
               !following.isRequiredPositional) {
             // The parameter to be removed and the following parameter are not
             // of the same kind, so there is a delimiter between them that we
@@ -85,8 +81,7 @@ class RemoveUnusedParameter extends ResolvedCorrectionProducer {
         }
       } else {
         var preceding = parameters[index - 1];
-        if (preceding.isRequiredPositional &&
-            !parameter_final.isRequiredPositional) {
+        if (preceding.isRequiredPositional && !parameter.isRequiredPositional) {
           // The parameter to be removed and the preceding parameter are not
           // of the same kind, so there is a delimiter between them.
           if (index == parameters.length - 1) {

pkg/analysis_server/lib/src/services/correction/dart/replace_null_with_closure.dart

@@ -26,7 +26,7 @@ class ReplaceNullWithClosure extends ResolvedCorrectionProducer {
 
   @override
   Future<void> compute(ChangeBuilder builder) async {
-    AstNode? nodeToFix;
+    AstNode nodeToFix;
     var parameters = const <FormalParameterElement>[];
 
     var coveringNode = this.coveringNode;
@@ -41,18 +41,17 @@ class ReplaceNullWithClosure extends ResolvedCorrectionProducer {
           }
         }
         nodeToFix = expression;
+      } else {
+        return;
       }
     } else if (coveringNode is NullLiteral) {
       nodeToFix = coveringNode;
-    }
-
-    if (nodeToFix == null) {
+    } else {
       return;
     }
 
-    var nodeToFix_final = nodeToFix;
     await builder.addDartFileEdit(file, (builder) {
-      builder.addReplacement(range.node(nodeToFix_final), (builder) {
+      builder.addReplacement(range.node(nodeToFix), (builder) {
         builder.writeFormalParameters(parameters);
         builder.write(' => null');
       });

pkg/analysis_server/lib/src/services/correction/dart/replace_with_null_aware.dart

@@ -45,11 +45,9 @@ class ReplaceWithNullAware extends ResolvedCorrectionProducer {
   }
 
   Future<void> _computeInChain(ChangeBuilder builder) async {
-    var node = coveringNode;
-    if (node is Expression) {
-      var node_final = node;
-      await builder.addDartFileEdit(file, (builder) {
-        var parent = node_final.parent;
+    await builder.addDartFileEdit(file, (builder) {
+      var node = coveringNode;
+      if (node case Expression(:var parent)) {
         while (parent != null) {
           if (parent is MethodInvocation && parent.target == node) {
             var operator = parent.operator;
@@ -62,10 +60,10 @@ class ReplaceWithNullAware extends ResolvedCorrectionProducer {
             break;
           }
           node = parent;
-          parent = node?.parent;
+          parent = node.parent;
         }
-      });
-    }
+      }
+    });
   }
 
   Future<void> _computeSingle(ChangeBuilder builder) async {

pkg/analysis_server/lib/src/services/correction/dart/update_sdk_constraints.dart

@@ -49,7 +49,7 @@ class UpdateSdkConstraints extends ResolvedCorrectionProducer {
       length = spaceOffset;
     }
 
-    String? newText;
+    String newText;
     if (text == 'any') {
       newText = '^$_minimumVersion';
     } else if (text.startsWith('^')) {
@@ -58,14 +58,12 @@ class UpdateSdkConstraints extends ResolvedCorrectionProducer {
       newText = '>=$_minimumVersion';
     } else if (text.startsWith('>')) {
       newText = '>=$_minimumVersion';
-    }
-    if (newText == null) {
+    } else {
       return;
     }
 
-    var newText_final = newText;
     await builder.addYamlFileEdit(pubspecFile.path, (builder) {
-      builder.addSimpleReplacement(SourceRange(offset, length), newText_final);
+      builder.addSimpleReplacement(SourceRange(offset, length), newText);
     });
   }