Remove BlockExpression from the Kernel language.

lib/ast.dart

Index: lib/ast.dart
diff --git a/lib/ast.dart b/lib/ast.dart
index aa2228581e456fe3164b650aeee3e4b5514198d3..d3ac0535120ef6a424910824a82164e3c91924dd 100644
--- a/lib/ast.dart
+++ b/lib/ast.dart
@@ -2411,36 +2411,6 @@ class Let extends Expression {
   }
 }
 
-class BlockExpression extends Expression {
-  Block body;
-  Expression value;
-
-  BlockExpression(this.body, this.value) {
-    body?.parent = this;
-    value?.parent = this;
-  }
-
-  DartType getStaticType(TypeEnvironment types) => value.getStaticType(types);
-
-  accept(ExpressionVisitor v) => v.visitBlockExpression(this);
-
-  visitChildren(Visitor v) {
-    body?.accept(v);
-    value?.accept(v);
-  }
-
-  transformChildren(Transformer v) {
-    if (body != null) {
-      body = body.accept(v);
-      body?.parent = this;
-    }
-    if (value != null) {
-      value = value.accept(v);
-      value?.parent = this;
-    }
-  }
-}
-
 // ------------------------------------------------------------------------
 //                              STATEMENTS
 // ------------------------------------------------------------------------