From the article "Can AI Generate Functional Terraform?"

add-iam-hcl

resource "aws_iam_policy" "lambda_s3" {
  name = "lambda_s3_policy"
  policy = jsonencode({
    Version = "2012-10-17",
    Statement = [{
      Effect   = "Allow",
      Action   = ["s3:GetObject", "s3:PutObject"],
      Resource = "${aws_s3_bucket.example.arn}/*"
    }]
  })
}

resource "aws_iam_role_policy_attachment" "lambda_attach" {
  role       = aws_iam_role.lambda_exec.name
  policy_arn = aws_iam_policy.lambda_s3.arn
}