fix a dce issue identified by ci

internal/bundler/bundler_dce_test.go

@@ -1030,15 +1030,15 @@ func TestDeadCodeFollowingJump(t *testing.T) {
 					if (true) return y + z()
 					if (FAIL) return FAIL
 					if (x) { var y }
-					function z() {}
+					function z() { KEEP_ME() }
 					return FAIL
 				}
 
 				function testThrow() {
 					if (true) throw y + z()
 					if (FAIL) return FAIL
 					if (x) { var y }
-					function z() {}
+					function z() { KEEP_ME() }
 					return FAIL
 				}
 
@@ -1050,7 +1050,7 @@ func TestDeadCodeFollowingJump(t *testing.T) {
 						}
 						if (FAIL) return FAIL
 						if (x) { var y }
-						function z() {}
+						function z() { KEEP_ME() }
 						return FAIL
 					}
 				}
@@ -1063,7 +1063,7 @@ func TestDeadCodeFollowingJump(t *testing.T) {
 						}
 						if (FAIL) return FAIL
 						if (x) { var y }
-						function z() {}
+						function z() { KEEP_ME() }
 						return FAIL
 					}
 				}

internal/bundler/snapshots/snapshots_dce.txt

@@ -18,13 +18,15 @@ function testReturn() {
   if (x)
     var y;
   function z() {
+    KEEP_ME();
   }
 }
 function testThrow() {
   throw y + z();
   if (x)
     var y;
   function z() {
+    KEEP_ME();
   }
 }
 function testBreak() {
@@ -34,6 +36,7 @@ function testBreak() {
     if (x)
       var y;
     function z() {
+      KEEP_ME();
     }
   }
 }
@@ -44,6 +47,7 @@ function testContinue() {
     if (x)
       var y;
     function z() {
+      KEEP_ME();
     }
   }
 }

internal/js_parser/js_parser.go

@@ -6022,6 +6022,14 @@ func shouldKeepStmtInDeadControlFlow(stmt js_ast.Stmt) bool {
 		s.Decls = identifiers
 		return true
 
+	case *js_ast.SBlock:
+		for _, child := range s.Stmts {
+			if shouldKeepStmtInDeadControlFlow(child) {
+				return true
+			}
+		}
+		return false
+
 	case *js_ast.SIf:
 		return shouldKeepStmtInDeadControlFlow(s.Yes) || (s.No != nil && shouldKeepStmtInDeadControlFlow(*s.No))
 
@@ -6113,30 +6121,13 @@ func (p *parser) visitStmts(stmts []js_ast.Stmt) []js_ast.Stmt {
 	visited := make([]js_ast.Stmt, 0, len(stmts))
 	var after []js_ast.Stmt
 	for _, stmt := range stmts {
-		var target *[]js_ast.Stmt
 		if _, ok := stmt.Data.(*js_ast.SExportEquals); ok {
 			// TypeScript "export = value;" becomes "module.exports = value;". This
 			// must happen at the end after everything is parsed because TypeScript
 			// moves this statement to the end when it generates code.
-			target = &after
+			after = p.visitAndAppendStmt(after, stmt)
 		} else {
-			target = &visited
-		}
-
-		// This call should only append new statements but never modify old ones
-		nextStmtIndex := len(*target)
-		*target = p.visitAndAppendStmt(*target, stmt)
-
-		// If there is a jump-like statement in the middle of this statement
-		// sequence, control flow is dead for all of the following statements.
-		// This improves dead-code elimination.
-		if p.options.mangleSyntax {
-			for _, stmt := range (*target)[nextStmtIndex:] {
-				if isJumpStatement(stmt.Data) {
-					p.isControlFlowDead = true
-					break
-				}
-			}
+			visited = p.visitAndAppendStmt(visited, stmt)
 		}
 	}
 	visited = append(visited, after...)