Revert "unreachable_from_main: Report unreachable constructors (#4162)" (#4253)

This reverts commit 6447552.

Author: pq

lib/src/rules/unreachable_from_main.dart

@@ -8,16 +8,15 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
-import 'package:collection/collection.dart';
 
 import '../analyzer.dart';
 
 const _desc = 'Unreachable top-level members in executable libraries.';
 
 const _details = r'''
-Top-level members and static members in an executable library should be used
-directly inside this library.  An executable library is a library that contains
-a `main` top-level function or that contains a top-level function annotated with
+Top-level members in an executable library should be used directly inside this
+library.  An executable library is a library that contains a `main` top-level
+function or that contains a top-level function annotated with
 `@pragma('vm:entry-point')`).  Executable libraries are not usually imported
 and it's better to avoid defining unused members.
 
@@ -44,7 +43,7 @@ void f() {}
 
 class UnreachableFromMain extends LintRule {
   static const LintCode code = LintCode('unreachable_from_main',
-      "Unreachable member '{0}' in an executable library.",
+      'Unreachable top-level member in an executable library.',
       correctionMessage: 'Try referencing the member or removing it.');
 
   UnreachableFromMain()
@@ -100,12 +99,7 @@ class _DeclarationGatherer {
   }
 
   void _addStaticMember(ClassMember member) {
-    if (member is ConstructorDeclaration) {
-      var e = member.declaredElement;
-      if (e != null && e.isPublic && member.parent is! EnumDeclaration) {
-        declarations.add(member);
-      }
-    } else if (member is FieldDeclaration && member.isStatic) {
+    if (member is FieldDeclaration && member.isStatic) {
       for (var field in member.fields.variables) {
         var e = field.declaredElement;
         if (e != null && e.isPublic) {
@@ -121,72 +115,20 @@ class _DeclarationGatherer {
   }
 }
 
-/// A visitor which gathers the declarations of the "references" it visits.
-///
-/// "References" are most often [SimpleIdentifier]s, but can also be other
-/// nodes which refer to a declaration.
-// TODO(srawlins): Add support for patterns.
-class _ReferenceVisitor extends RecursiveAstVisitor {
+/// A visitor which gathers the declarations of the identifiers it visits.
+class _IdentifierVisitor extends RecursiveAstVisitor {
   Map<Element, Declaration> declarationMap;
 
   Set<Declaration> declarations = {};
 
-  _ReferenceVisitor(this.declarationMap);
-
-  @override
-  void visitAnnotation(Annotation node) {
-    var e = node.element;
-    if (e != null) {
-      _addDeclaration(e);
-    }
-    super.visitAnnotation(node);
-  }
+  _IdentifierVisitor(this.declarationMap);
 
   @override
   void visitAssignmentExpression(AssignmentExpression node) {
     _visitCompoundAssignmentExpression(node);
     super.visitAssignmentExpression(node);
   }
 
-  @override
-  void visitClassDeclaration(ClassDeclaration node) {
-    var element = node.declaredElement;
-    if (element != null) {
-      var hasConstructors =
-          node.members.any((e) => e is ConstructorDeclaration);
-      if (!hasConstructors) {
-        // The default constructor will have an implicit super-initializer to
-        // the super-type's unnamed constructor.
-        _addDefaultSuperConstructorDeclaration(node);
-      }
-    }
-    super.visitClassDeclaration(node);
-  }
-
-  @override
-  void visitConstructorDeclaration(ConstructorDeclaration node) {
-    // If a constructor does not have an explicit super-initializer (or redirection?)
-    // then it has an implicit super-initializer to the super-type's unnamed constructor.
-    var hasSuperInitializer =
-        node.initializers.any((e) => e is SuperConstructorInvocation);
-    if (!hasSuperInitializer) {
-      var enclosingClass = node.parent;
-      if (enclosingClass is ClassDeclaration) {
-        _addDefaultSuperConstructorDeclaration(enclosingClass);
-      }
-    }
-    super.visitConstructorDeclaration(node);
-  }
-
-  @override
-  void visitConstructorName(ConstructorName node) {
-    var e = node.staticElement;
-    if (e != null) {
-      _addDeclaration(e);
-    }
-    super.visitConstructorName(node);
-  }
-
   @override
   void visitPostfixExpression(PostfixExpression node) {
     _visitCompoundAssignmentExpression(node);
@@ -199,16 +141,6 @@ class _ReferenceVisitor extends RecursiveAstVisitor {
     super.visitPrefixExpression(node);
   }
 
-  @override
-  void visitRedirectingConstructorInvocation(
-      RedirectingConstructorInvocation node) {
-    var element = node.staticElement;
-    if (element != null) {
-      _addDeclaration(element);
-    }
-    super.visitRedirectingConstructorInvocation(node);
-  }
-
   @override
   void visitSimpleIdentifier(SimpleIdentifier node) {
     if (!node.inDeclarationContext()) {
@@ -220,15 +152,6 @@ class _ReferenceVisitor extends RecursiveAstVisitor {
     super.visitSimpleIdentifier(node);
   }
 
-  @override
-  void visitSuperConstructorInvocation(SuperConstructorInvocation node) {
-    var e = node.staticElement;
-    if (e != null) {
-      _addDeclaration(e);
-    }
-    super.visitSuperConstructorInvocation(node);
-  }
-
   /// Adds the declaration of the top-level element which contains [element] to
   /// [declarations], if it is found in [declarationMap].
   ///
@@ -244,8 +167,8 @@ class _ReferenceVisitor extends RecursiveAstVisitor {
       declarations.add(enclosingTopLevelDeclaration);
     }
 
-    // Also add [element]'s declaration if it is a constructor, static accessor,
-    // or static method.
+    // Also add [element]'s declaration if it is a static accessor or static
+    // method.
     if (element.isPrivate) {
       return;
     }
@@ -255,7 +178,7 @@ class _ReferenceVisitor extends RecursiveAstVisitor {
     }
     if (enclosingElement is InterfaceElement ||
         enclosingElement is ExtensionElement) {
-      if (element is ConstructorElement) {
+      if (element is PropertyAccessorElement && element.isStatic) {
         var declaration = declarationMap[element];
         if (declaration != null) {
           declarations.add(declaration);
@@ -265,23 +188,6 @@ class _ReferenceVisitor extends RecursiveAstVisitor {
         if (declaration != null) {
           declarations.add(declaration);
         }
-      } else if (element is PropertyAccessorElement && element.isStatic) {
-        var declaration = declarationMap[element];
-        if (declaration != null) {
-          declarations.add(declaration);
-        }
-      }
-    }
-  }
-
-  void _addDefaultSuperConstructorDeclaration(ClassDeclaration class_) {
-    var classElement = class_.declaredElement;
-    var supertype = classElement?.supertype;
-    if (supertype != null) {
-      var unnamedConstructor =
-          supertype.constructors.firstWhereOrNull((e) => e.name.isEmpty);
-      if (unnamedConstructor != null) {
-        _addDeclaration(unnamedConstructor);
       }
     }
   }
@@ -335,14 +241,13 @@ class _Visitor extends SimpleAstVisitor<void> {
       }
     }
 
-    // The set of the declarations which each top-level and static declaration
-    // references.
+    // The set of the declarations which each top-level declaration references.
     var dependencies = <Declaration, Set<Declaration>>{};
 
     // Map each declaration to the collection of declarations which are
     // referenced within its body.
     for (var declaration in declarations) {
-      var visitor = _ReferenceVisitor(declarationByElement);
+      var visitor = _IdentifierVisitor(declarationByElement);
       declaration.accept(visitor);
       dependencies[declaration] = visitor.declarations;
     }
@@ -371,25 +276,15 @@ class _Visitor extends SimpleAstVisitor<void> {
     });
 
     for (var member in unusedMembers) {
-      if (member is ConstructorDeclaration) {
-        if (member.name == null) {
-          rule.reportLint(member.returnType, arguments: [member.nameForError]);
-        } else {
-          rule.reportLintForToken(member.name,
-              arguments: [member.nameForError]);
-        }
-      } else if (member is NamedCompilationUnitMember) {
-        rule.reportLintForToken(member.name, arguments: [member.nameForError]);
+      if (member is NamedCompilationUnitMember) {
+        rule.reportLintForToken(member.name);
       } else if (member is VariableDeclaration) {
-        rule.reportLintForToken(member.name, arguments: [member.nameForError]);
+        rule.reportLintForToken(member.name);
       } else if (member is ExtensionDeclaration) {
-        var memberName = member.name;
         rule.reportLintForToken(
-            memberName ?? member.firstTokenAfterCommentAndMetadata,
-            arguments: [member.nameForError]);
+            member.name ?? member.firstTokenAfterCommentAndMetadata);
       } else {
-        rule.reportLintForToken(member.firstTokenAfterCommentAndMetadata,
-            arguments: [member.nameForError]);
+        rule.reportLintForToken(member.firstTokenAfterCommentAndMetadata);
       }
     }
   }
@@ -428,28 +323,3 @@ extension on Annotation {
     return type is InterfaceType && type.element.isPragma;
   }
 }
-
-extension on Declaration {
-  String get nameForError {
-    // TODO(srawlins): Move this to analyzer when other uses are found.
-    // TODO(srawlins): Convert to switch-expression, hopefully.
-    var self = this;
-    if (self is ConstructorDeclaration) {
-      return self.name?.lexeme ?? self.returnType.name;
-    } else if (self is EnumConstantDeclaration) {
-      return self.name.lexeme;
-    } else if (self is ExtensionDeclaration) {
-      var name = self.name;
-      return name?.lexeme ?? 'the unnamed extension';
-    } else if (self is MethodDeclaration) {
-      return self.name.lexeme;
-    } else if (self is NamedCompilationUnitMember) {
-      return self.name.lexeme;
-    } else if (self is VariableDeclaration) {
-      return self.name.lexeme;
-    }
-
-    assert(false, 'Uncovered Declaration subtype: ${self.runtimeType}');
-    return '';
-  }
-}