Revert "Start formatting patterns and other related syntax. (#1165)" (#1166)

This reverts commit b5ad63e.

Author: munificent

lib/src/dart_formatter.dart

@@ -90,10 +90,6 @@ class DartFormatter {
     var featureSet = FeatureSet.fromEnableFlags2(
       sdkLanguageVersion: Version(2, 19, 0),
       flags: [
-        // TODO(rnystrom): This breaks existing switch cases containing constant
-        // expressions that aren't valid patterns. See:
-        // https://github.com/dart-lang/dart_style/issues/1164
-        'patterns',
         'records',
         'unnamed-libraries',
       ],

lib/src/source_visitor.dart

@@ -359,10 +359,11 @@ class SourceVisitor extends ThrowingAstVisitor {
     // appears before the first operand.
     builder.startLazyRule();
 
-    // Flatten out a tree/chain of the same precedence. If we need to split on
-    // any of them, we split on all of them.
+    // Flatten out a tree/chain of the same precedence. If we split on this
+    // precedence level, we will break all of them.
     var precedence = node.operator.type.precedence;
 
+    @override
     void traverse(Expression e) {
       if (e is BinaryExpression && e.operator.type.precedence == precedence) {
         traverse(e.leftOperand);
@@ -390,46 +391,6 @@ class SourceVisitor extends ThrowingAstVisitor {
     builder.endRule();
   }
 
-  @override
-  void visitBinaryPattern(BinaryPattern node) {
-    builder.startSpan();
-    builder.nestExpression(now: true);
-
-    // Start lazily so we don't force the operator to split if a line comment
-    // appears before the first operand.
-    builder.startLazyRule();
-
-    // Flatten out a tree/chain of the same precedence. If we need to split on
-    // any of them, we split on all of them.
-    var precedence = node.operator.type.precedence;
-
-    void traverse(DartPattern p) {
-      if (p is BinaryPattern && p.operator.type.precedence == precedence) {
-        traverse(p.leftOperand);
-
-        space();
-        token(p.operator);
-
-        split();
-        traverse(p.rightOperand);
-      } else {
-        visit(p);
-      }
-    }
-
-    // Blocks as operands to infix patterns should always nest like regular
-    // operands.
-    builder.startBlockArgumentNesting();
-
-    traverse(node);
-
-    builder.endBlockArgumentNesting();
-
-    builder.unnest();
-    builder.endSpan();
-    builder.endRule();
-  }
-
   @override
   void visitBlock(Block node) {
     // Treat empty blocks specially. In most cases, they are not allowed to
@@ -794,12 +755,6 @@ class SourceVisitor extends ThrowingAstVisitor {
     visit(node.uri);
   }
 
-  @override
-  void visitConstantPattern(ConstantPattern node) {
-    token(node.constKeyword, after: space);
-    visit(node.expression);
-  }
-
   @override
   void visitConstructorDeclaration(ConstructorDeclaration node) {
     visitMetadata(node.metadata);
@@ -1819,8 +1774,12 @@ class SourceVisitor extends ThrowingAstVisitor {
 
     var hasInnerControlFlow = false;
     for (var element in ifElements) {
-      _visitIfCondition(element.ifKeyword, element.leftParenthesis,
-          element.condition, element.caseClause, element.rightParenthesis);
+      // The condition.
+      token(element.ifKeyword);
+      space();
+      token(element.leftParenthesis);
+      visit(element.condition);
+      token(element.rightParenthesis);
 
       visitChild(element, element.thenElement);
       if (element.thenElement.isControlFlowElement) {
@@ -1863,8 +1822,13 @@ class SourceVisitor extends ThrowingAstVisitor {
 
   @override
   void visitIfStatement(IfStatement node) {
-    _visitIfCondition(node.ifKeyword, node.leftParenthesis, node.condition,
-        node.caseClause, node.rightParenthesis);
+    builder.nestExpression();
+    token(node.ifKeyword);
+    space();
+    token(node.leftParenthesis);
+    visit(node.condition);
+    token(node.rightParenthesis);
+    builder.unnest();
 
     void visitClause(Statement clause) {
       if (clause is Block || clause is IfStatement) {
@@ -2258,15 +2222,6 @@ class SourceVisitor extends ThrowingAstVisitor {
     token(node.rightParenthesis);
   }
 
-  @override
-  void visitParenthesizedPattern(ParenthesizedPattern node) {
-    builder.nestExpression();
-    token(node.leftParenthesis);
-    visit(node.pattern);
-    builder.unnest();
-    token(node.rightParenthesis);
-  }
-
   @override
   void visitPartDirective(PartDirective node) {
     _visitDirectiveMetadata(node);
@@ -2447,13 +2402,6 @@ class SourceVisitor extends ThrowingAstVisitor {
     });
   }
 
-  @override
-  void visitRelationalPattern(RelationalPattern node) {
-    token(node.operator);
-    space();
-    visit(node.operand);
-  }
-
   @override
   void visitRethrowExpression(RethrowExpression node) {
     token(node.rethrowKeyword);
@@ -2590,6 +2538,7 @@ class SourceVisitor extends ThrowingAstVisitor {
     token(node.colon);
 
     builder.indent();
+    // TODO(rnystrom): Allow inline cases?
     newline();
 
     visitNodes(node.statements, between: oneOrTwoNewlines);
@@ -2603,29 +2552,7 @@ class SourceVisitor extends ThrowingAstVisitor {
     token(node.colon);
 
     builder.indent();
-    newline();
-
-    visitNodes(node.statements, between: oneOrTwoNewlines);
-    builder.unindent();
-  }
-
-  @override
-  void visitSwitchPatternCase(SwitchPatternCase node) {
-    _visitLabels(node.labels);
-
-    token(node.keyword);
-    space();
-
-    builder.startBlockArgumentNesting();
-    builder.nestExpression();
-    visit(node.guardedPattern.pattern);
-    builder.unnest();
-    builder.endBlockArgumentNesting();
-
-    visit(node.guardedPattern.whenClause);
-    token(node.colon);
-
-    builder.indent();
+    // TODO(rnystrom): Allow inline cases?
     newline();
 
     visitNodes(node.statements, between: oneOrTwoNewlines);
@@ -2784,20 +2711,6 @@ class SourceVisitor extends ThrowingAstVisitor {
     });
   }
 
-  @override
-  void visitWhenClause(WhenClause node) {
-    builder.startRule();
-    split();
-    token(node.whenKeyword);
-    space();
-    builder.startBlockArgumentNesting();
-    builder.nestExpression();
-    visit(node.expression);
-    builder.unnest();
-    builder.endBlockArgumentNesting();
-    builder.endRule();
-  }
-
   @override
   void visitWhileStatement(WhileStatement node) {
     builder.nestExpression();
@@ -3417,45 +3330,6 @@ class SourceVisitor extends ThrowingAstVisitor {
     builder.endRule();
   }
 
-  /// Visits the `if (<expr> [case <pattern> [when <expr>]])` header of an if
-  /// statement or element.
-  void _visitIfCondition(Token ifKeyword, Token leftParenthesis,
-      AstNode condition, CaseClause? caseClause, Token rightParenthesis) {
-    builder.nestExpression();
-    token(ifKeyword);
-    space();
-    token(leftParenthesis);
-
-    if (caseClause != null) {
-      // Wrap the rule for splitting before "case" around the value expression
-      // so that if the value splits, we split before "case" too.
-      builder.startRule();
-
-      // Nest the condition so that it indents deeper than the case clause.
-      builder.nestExpression();
-    }
-
-    visit(condition);
-
-    // If-case clause.
-    if (caseClause != null) {
-      split();
-      token(caseClause.caseKeyword);
-      space();
-      builder.startBlockArgumentNesting();
-      builder.nestExpression();
-      visit(caseClause.guardedPattern.pattern);
-      builder.unnest();
-      builder.endBlockArgumentNesting();
-      builder.endRule();
-      visit(caseClause.guardedPattern.whenClause);
-    }
-
-    token(rightParenthesis);
-    if (caseClause != null) builder.unnest();
-    builder.unnest();
-  }
-
   /// Writes the separator between a type annotation and a variable or
   /// parameter. If the preceding type annotation ends in a delimited list of
   /// elements that have block formatting, then we don't split between the