public static Map<ASTNode, RexNode> genExprNodeJoinCond(ASTNode expr, TypeCheckCtx tcCtx, RexBuilder rexBuilder)
      throws SemanticException {
    JoinCondTypeCheckProcFactory<RexNode> typeCheckProcFactory =
        new JoinCondTypeCheckProcFactory<>(new RexNodeExprFactory(rexBuilder));
    return typeCheckProcFactory.genExprNode(expr, tcCtx);
  }
Given an AST join expression and a context, it will produce a map from AST nodes
to Calcite RexNode.
ql/src/java/org/apache/hadoop/hive/ql/parse/type/RexNodeTypeCheck.java