Parameter $1 for postgres is not supported

[eric-zhu]

In version v18.8.0, heredoc strings support was added, and "$": TokenType.PARAMETER was replaced with "$": TokenType.HEREDOC_STRING. Since then, sql query with a parameter like $1 cannot be parsed.

Here is the original PR Feat!: add support for heredoc strings (Postgres, ClickHouse) #2328

Fully reproducible code snippet

import sqlglot
from sqlglot.optimizer.annotate_types import annotate_types
from sqlglot.optimizer.qualify import qualify

schema = {"t": {"x": "text"}}
sql = "select x from t where $1::text = 'ok'"
expression = sqlglot.parse_one(sql, dialect="postgres")
print(expression.sql(dialect="postgres"))
qualified_expr = qualify(expression, schema=schema, dialect="postgres")
annotated_expr = annotate_types(qualified_expr, schema=schema)
print(annotated_expr.selects[0].type)

Exception was raised. Expected output is TEXT.

Traceback (most recent call last):
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/tokens.py", line 836, in tokenize
    self._scan()
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/tokens.py", line 859, in _scan
    self._scan_keywords()
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/tokens.py", line 994, in _scan_keywords
    if self._scan_string(word):
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/tokens.py", line 1136, in _scan_string
    tag = "" if self._char == end else self._extract_string(end)
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/tokens.py", line 1203, in _extract_string
    raise TokenError(f"Missing {delimiter} from {self._line}:{self._start}")
sqlglot.errors.TokenError: Missing $ from 1:22

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/eric/tmp/test.py", line 20, in <module>
    expression = sqlglot.parse_one(sql, dialect="postgres")
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/__init__.py", line 125, in parse_one
    result = dialect.parse(sql, **opts)
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/dialects/dialect.py", line 304, in parse
    return self.parser(**opts).parse(self.tokenize(sql), sql)
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/dialects/dialect.py", line 318, in tokenize
    return self.tokenizer.tokenize(sql)
  File "/Users/eric/venv/lib/python3.10/site-packages/sqlglot/tokens.py", line 841, in tokenize
    raise TokenError(f"Error tokenizing '{context}'") from e
sqlglot.errors.TokenError: Error tokenizing 'select x from t where $1::text = 'ok'