Add support for labeled break/continue

This requires an additional field to Flow that maps user-defined
statement labels to the internal Binaryen labels passed to module.br().
Thanks to the existing logic to handle unlabeled break/continue, adding
support for labeled break/continue is a breeze.

Fixes #2889.

Author: CountBleck

src/compiler.ts

@@ -2290,6 +2290,8 @@ export class Compiler extends DiagnosticEmitter {
   private compileBlockStatement(
     statement: BlockStatement
   ): ExpressionRef {
+    if (statement.label) return this.compileLabeledBlockStatement(statement);
+
     let statements = statement.statements;
     let outerFlow = this.currentFlow;
     let innerFlow = outerFlow.fork();
@@ -2301,6 +2303,30 @@ export class Compiler extends DiagnosticEmitter {
     return this.module.flatten(stmts);
   }
 
+  private compileLabeledBlockStatement(
+    statement: BlockStatement
+  ): ExpressionRef {
+    let statements = statement.statements;
+    let outerFlow = this.currentFlow;
+    let innerFlow = outerFlow.fork();
+
+    let labelNode = assert(statement.label);
+    let label = innerFlow.pushControlFlowLabel();
+    let breakLabel = `block-break|${label}`;
+    innerFlow.addUserLabel(labelNode.text, breakLabel, null, labelNode);
+    this.currentFlow = innerFlow;
+
+    let stmts = this.compileStatements(statements);
+    innerFlow.popControlFlowLabel(label);
+    innerFlow.removeUserLabel(labelNode.text);
+
+    outerFlow.inherit(innerFlow);
+    this.currentFlow = outerFlow;
+    return innerFlow.isAny(FlowFlags.Breaks | FlowFlags.ConditionallyBreaks)
+      ? this.module.block(breakLabel, stmts)
+      : this.module.flatten(stmts);
+  }
+
   private compileTypeDeclaration(statement: TypeDeclaration): ExpressionRef {
     let flow = this.currentFlow;
     let name = statement.name.text;
@@ -2324,23 +2350,25 @@ export class Compiler extends DiagnosticEmitter {
   ): ExpressionRef {
     let module = this.module;
     let labelNode = statement.label;
+    let flow = this.currentFlow;
+    let breakLabel: string | null = null;
     if (labelNode) {
-      this.error(
-        DiagnosticCode.Not_implemented_0,
-        labelNode.range,
-        "Break label"
-      );
-      return module.unreachable();
+      const userLabel = flow.getUserLabel(labelNode.text);
+      if (userLabel) breakLabel = userLabel.breakLabel;
+    } else {
+      breakLabel = flow.breakLabel;
     }
-    let flow = this.currentFlow;
-    let breakLabel = flow.breakLabel;
+
     if (breakLabel == null) {
       this.error(
-        DiagnosticCode.A_break_statement_can_only_be_used_within_an_enclosing_iteration_or_switch_statement,
+        labelNode
+          ? DiagnosticCode.A_break_statement_can_only_jump_to_a_label_of_an_enclosing_statement
+          : DiagnosticCode.A_break_statement_can_only_be_used_within_an_enclosing_iteration_or_switch_statement,
         statement.range
       );
       return module.unreachable();
     }
+
     flow.set(FlowFlags.Breaks);
     return module.br(breakLabel);
   }
@@ -2349,25 +2377,27 @@ export class Compiler extends DiagnosticEmitter {
     statement: ContinueStatement
   ): ExpressionRef {
     let module = this.module;
-    let label = statement.label;
-    if (label) {
-      this.error(
-        DiagnosticCode.Not_implemented_0,
-        label.range,
-        "Continue label"
-      );
-      return module.unreachable();
+    let labelNode = statement.label;
+    let flow = this.currentFlow;
+    let continueLabel: string | null = null;
+    if (labelNode) {
+      const userLabel = flow.getUserLabel(labelNode.text);
+      if (userLabel) continueLabel = userLabel.continueLabel;
+    } else {
+      continueLabel = flow.continueLabel;
     }
+
     // Check if 'continue' is allowed here
-    let flow = this.currentFlow;
-    let continueLabel = flow.continueLabel;
     if (continueLabel == null) {
       this.error(
-        DiagnosticCode.A_continue_statement_can_only_be_used_within_an_enclosing_iteration_statement,
+        labelNode
+          ? DiagnosticCode.A_continue_statement_can_only_jump_to_a_label_of_an_enclosing_iteration_statement
+          : DiagnosticCode.A_continue_statement_can_only_be_used_within_an_enclosing_iteration_statement,
         statement.range
       );
       return module.unreachable();
     }
+
     flow.set(FlowFlags.Continues | FlowFlags.Terminates);
     return module.br(continueLabel);
   }
@@ -2409,6 +2439,8 @@ export class Compiler extends DiagnosticEmitter {
     let continueLabel = `do-continue|${label}`;
     flow.continueLabel = continueLabel;
     let loopLabel = `do-loop|${label}`;
+    let labelNode = statement.label;
+    if (labelNode) flow.addUserLabel(labelNode.text, breakLabel, continueLabel, labelNode);
     this.currentFlow = flow;
     let bodyStmts = new Array<ExpressionRef>();
     let body = statement.body;
@@ -2418,6 +2450,7 @@ export class Compiler extends DiagnosticEmitter {
       bodyStmts.push(this.compileStatement(body));
     }
     flow.popControlFlowLabel(label);
+    if (labelNode) flow.removeUserLabel(labelNode.text);
 
     let possiblyContinues = flow.isAny(FlowFlags.Continues | FlowFlags.ConditionallyContinues);
     let possiblyBreaks = flow.isAny(FlowFlags.Breaks | FlowFlags.ConditionallyBreaks);
@@ -2573,6 +2606,8 @@ export class Compiler extends DiagnosticEmitter {
     bodyFlow.breakLabel = breakLabel;
     let continueLabel = `for-continue|${label}`;
     bodyFlow.continueLabel = continueLabel;
+    let labelNode = statement.label;
+    if (labelNode) bodyFlow.addUserLabel(labelNode.text, breakLabel, continueLabel, labelNode);
     let loopLabel = `for-loop|${label}`;
     this.currentFlow = bodyFlow;
     let bodyStmts = new Array<ExpressionRef>();
@@ -2583,6 +2618,7 @@ export class Compiler extends DiagnosticEmitter {
       bodyStmts.push(this.compileStatement(body));
     }
     bodyFlow.popControlFlowLabel(label);
+    if (labelNode) bodyFlow.removeUserLabel(labelNode.text);
     bodyFlow.breakLabel = null;
     bodyFlow.continueLabel = null;
 
@@ -2683,17 +2719,27 @@ export class Compiler extends DiagnosticEmitter {
     );
     let condKind = this.evaluateCondition(condExprTrueish);
 
+    let flow = this.currentFlow;
+    let label = -1;
+    let labelNode = statement.label;
+    let breakLabel: string | null = null;
+    if (labelNode) {
+      label = flow.pushControlFlowLabel();
+      breakLabel = `if-break|${label}`;
+      flow.addUserLabel(labelNode.text, breakLabel, null, labelNode);
+    }
+
     // Shortcut if the condition is constant
     switch (condKind) {
       case ConditionKind.True: {
-        return module.block(null, [
+        return module.block(breakLabel, [
           module.drop(condExprTrueish),
           this.compileStatement(ifTrue)
         ]);
       }
       case ConditionKind.False: {
         return ifFalse
-          ? module.block(null, [
+          ? module.block(breakLabel, [
               module.drop(condExprTrueish),
               this.compileStatement(ifFalse)
             ])
@@ -2703,8 +2749,6 @@ export class Compiler extends DiagnosticEmitter {
 
     // From here on condition is always unknown
 
-    let flow = this.currentFlow;
-
     // Compile ifTrue assuming the condition turned out true
     let thenStmts = new Array<ExpressionRef>();
     let thenFlow = flow.forkThen(condExpr);
@@ -2717,6 +2761,7 @@ export class Compiler extends DiagnosticEmitter {
     this.currentFlow = flow;
 
     // Compile ifFalse assuming the condition turned out false, if present
+    let expr: ExpressionRef;
     let elseFlow = flow.forkElse(condExpr);
     if (ifFalse) {
       this.currentFlow = elseFlow;
@@ -2728,7 +2773,7 @@ export class Compiler extends DiagnosticEmitter {
       }
       flow.inheritAlternatives(thenFlow, elseFlow); // terminates if both do
       this.currentFlow = flow;
-      return module.if(condExprTrueish,
+      expr = module.if(condExprTrueish,
         module.flatten(thenStmts),
         module.flatten(elseStmts)
       );
@@ -2742,10 +2787,15 @@ export class Compiler extends DiagnosticEmitter {
         flow.inheritAlternatives(thenFlow, elseFlow);
       }
       this.currentFlow = flow;
-      return module.if(condExprTrueish,
+      expr = module.if(condExprTrueish,
         module.flatten(thenStmts)
       );
     }
+
+    if (!labelNode) return expr;
+    flow.popControlFlowLabel(label);
+    flow.removeUserLabel(labelNode.text);
+    return module.block(breakLabel, [expr]);
   }
 
   private compileReturnStatement(
@@ -2802,6 +2852,7 @@ export class Compiler extends DiagnosticEmitter {
   ): ExpressionRef {
     let module = this.module;
     let cases = statement.cases;
+    let labelNode = statement.label;
     let numCases = cases.length;
 
     // Compile the condition (always executes)
@@ -2824,6 +2875,9 @@ export class Compiler extends DiagnosticEmitter {
     let breakIndex = 1;
     let defaultIndex = -1;
     let label = outerFlow.pushControlFlowLabel();
+    let breakLabel = `break|${label}`;
+    if (labelNode) outerFlow.addUserLabel(labelNode.text, breakLabel, null, labelNode);
+
     for (let i = 0; i < numCases; ++i) {
       let case_ = cases[i];
       if (case_.isDefault) {
@@ -2843,7 +2897,7 @@ export class Compiler extends DiagnosticEmitter {
     // If there is a default case, break to it, otherwise break out of the switch
     breaks[breakIndex] = module.br(defaultIndex >= 0
       ? `case${defaultIndex}|${label}`
-      : `break|${label}`
+      : breakLabel
     );
 
     // Nest the case blocks in order, to be targeted by the br_if sequence
@@ -2859,7 +2913,6 @@ export class Compiler extends DiagnosticEmitter {
       let innerFlow = outerFlow.fork(/* newBreakContext */ true, /* newContinueContext */ false);
       if (fallThroughFlow) innerFlow.mergeBranch(fallThroughFlow);
       this.currentFlow = innerFlow;
-      let breakLabel = `break|${label}`;
       innerFlow.breakLabel = breakLabel;
 
       let isLast = i == numCases - 1;
@@ -2897,6 +2950,7 @@ export class Compiler extends DiagnosticEmitter {
       currentBlock = module.block(nextLabel, stmts, TypeRef.None); // must be a labeled block
     }
     outerFlow.popControlFlowLabel(label);
+    if (labelNode) outerFlow.removeUserLabel(labelNode.text);
 
     // If the switch has a default, we only get past through any breaking flow
     if (defaultIndex >= 0) {
@@ -3208,6 +3262,8 @@ export class Compiler extends DiagnosticEmitter {
     thenFlow.breakLabel = breakLabel;
     let continueLabel = `while-continue|${label}`;
     thenFlow.continueLabel = continueLabel;
+    let labelNode = statement.label;
+    if (labelNode) thenFlow.addUserLabel(labelNode.text, breakLabel, continueLabel, labelNode);
     this.currentFlow = thenFlow;
     let bodyStmts = new Array<ExpressionRef>();
     let body = statement.body;
@@ -3220,6 +3276,7 @@ export class Compiler extends DiagnosticEmitter {
       module.br(continueLabel)
     );
     thenFlow.popControlFlowLabel(label);
+    if (labelNode) thenFlow.removeUserLabel(labelNode.text);
 
     let possiblyContinues = thenFlow.isAny(FlowFlags.Continues | FlowFlags.ConditionallyContinues);
     let possiblyBreaks = thenFlow.isAny(FlowFlags.Breaks | FlowFlags.ConditionallyBreaks);

src/diagnosticMessages.json

@@ -94,6 +94,8 @@
   "Type expected.": 1110,
   "A 'default' clause cannot appear more than once in a 'switch' statement.": 1113,
   "Duplicate label '{0}'.": 1114,
+  "A 'continue' statement can only jump to a label of an enclosing iteration statement.": 1115,
+  "A 'break' statement can only jump to a label of an enclosing statement": 1116,
   "An export assignment cannot have modifiers.": 1120,
   "Octal literals are not allowed in strict mode.": 1121,
   "Digit expected.": 1124,

src/flow.ts

@@ -199,6 +199,15 @@ export const enum ConditionKind {
   False
 }
 
+class UserLabels {
+  constructor(
+    /** The label we break to when encountering a break statement. */
+    readonly breakLabel: string,
+    /** The label we break to when encountering a continue statement. */
+    readonly continueLabel: string | null
+  ) {}
+}
+
 /** A control flow evaluator. */
 export class Flow {
 
@@ -245,10 +254,12 @@ export class Flow {
   outer: Flow | null = null;
   /** Flow flags indicating specific conditions. */
   flags: FlowFlags = FlowFlags.None;
-  /** The label we break to when encountering a continue statement. */
+  /** The label we break to when encountering an unlabeled continue statement. */
   continueLabel: string | null = null;
-  /** The label we break to when encountering a break statement. */
+  /** The label we break to when encountering an unlabeled break statement. */
   breakLabel: string | null = null;
+  /** Map of user-declared statement label names to internal label names */
+  userLabelMap: Map<string,UserLabels> | null = null;
   /** Scoped local variables. */
   scopedLocals: Map<string,Local> | null = null;
   /** Scoped type alias. */
@@ -351,6 +362,9 @@ export class Flow {
     } else {
       branch.continueLabel = this.continueLabel;
     }
+    let userLabelMap = this.userLabelMap;
+    if (userLabelMap) userLabelMap = cloneMap(userLabelMap);
+    branch.userLabelMap = userLabelMap;
     branch.localFlags = this.localFlags.slice();
     if (this.sourceFunction.is(CommonFlags.Constructor)) {
       let thisFieldFlags = assert(this.thisFieldFlags);
@@ -447,6 +461,33 @@ export class Flow {
     return local;
   }
 
+
+  /** Gets the internal labels associated with a user-declared label name. */
+  getUserLabel(name: string): UserLabels | null {
+    const userLabelMap = this.userLabelMap;
+    if (userLabelMap && userLabelMap.has(name)) return assert(userLabelMap.get(name));
+    return null;
+  }
+
+  /** Associates a user-declared label name with internal labels. */
+  addUserLabel(name: string, breakLabel: string, continueLabel: string | null, declarationNode: Node): void {
+    let userLabelMap = this.userLabelMap;
+    if (!userLabelMap) {
+      this.userLabelMap = userLabelMap = new Map();
+    } else if (userLabelMap.has(name)) {
+      this.program.error(DiagnosticCode.Duplicate_label_0, declarationNode.range, name);
+    }
+
+    userLabelMap.set(name, new UserLabels(breakLabel, continueLabel));
+  }
+
+  /** Remove a user-declared label name. */
+  removeUserLabel(name: string): void {
+    let userLabelMap = assert(this.userLabelMap);
+    assert(userLabelMap.has(name));
+    userLabelMap.delete(name);
+  }
+
   /** Gets the scoped local of the specified name. */
   getScopedLocal(name: string): Local | null {
     let scopedLocals = this.scopedLocals;