[Peter Hayes (HTMLPETE)]

Closes #11927

This change adds support for reversed binary comparison forms in staticExpressions.ts:

• (tuple) [op] sys.version_info
• (int) [op] sys.version_info[0]
• 'string' [op] sys.platform
• 'string' [op] os.name

Previously, only expressions with sys.version_info, sys.platform, or os.name on the left-hand side were statically evaluated for reachability and type checking.

Includes regression test coverage in StaticExpression3.

[Heejae Chang (heejaechang)]

🔴 Pyright CLI QA — 2c3eef9f — verdict: red

Automated CLI checks compared this change with its base revision.
27 focused check(s) completed.

Needs review: reportAssignmentType no longer reported

The base reports reportAssignmentType for this example; the PR does not. Is this change intended?

Reproduction and observed results

Create these files in an empty directory:

main.py

reveal_type(0)
import sys
if (3, 13) < sys.version_info:
    value: int = "not an int"

pyrightconfig.json

{
  "include": [
    "main.py"
  ],
  "pythonVersion": "3.13",
  "pythonPlatform": "Linux",
  "typeCheckingMode": "basic"
}

From that directory, run each built Pyright revision:

node <pyright-cli-entrypoint> --outputjson -p .

Base e6d4bda989a07e384ed087ce73af5b6b4d69b64d

{
  "exit_code": 1,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "error",
      "rule": "reportAssignmentType",
      "message": "Type \"Literal['not an int']\" is not assignable to declared type \"int\"\n  \"Literal['not an int']\" is not assignable to \"int\"",
      "range": {
        "start": [
          3,
          17
        ],
        "end": [
          3,
          29
        ]
      }
    },
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

PR 2c3eef9fef402248c1cee0345dfd26a4f49ebaad

{
  "exit_code": 0,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

Diagnostic ranges use zero-based line and character positions.

Needs review: reportAttributeAccessIssue newly reported

The PR reports reportAttributeAccessIssue for this example; the base does not. Is this change intended?

Reproduction and observed results

Create these files in an empty directory:

main.py

reveal_type(0)
import sys
from dataclasses import dataclass
from typing import assert_type
@dataclass(frozen=b"linux" == sys.platform)
class Record:
    value: int
record = Record(1)
assert_type(record.value, int)
record.value = 2

pyrightconfig.json

{
  "include": [
    "main.py"
  ],
  "pythonVersion": "3.13",
  "pythonPlatform": "Linux",
  "typeCheckingMode": "basic"
}

From that directory, run each built Pyright revision:

node <pyright-cli-entrypoint> --outputjson -p .

Base e6d4bda989a07e384ed087ce73af5b6b4d69b64d

{
  "exit_code": 0,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

PR 2c3eef9fef402248c1cee0345dfd26a4f49ebaad

{
  "exit_code": 1,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "error",
      "rule": "reportAttributeAccessIssue",
      "message": "Cannot assign to attribute \"value\" for class \"Record\"\n  Attribute \"value\" is read-only",
      "range": {
        "start": [
          9,
          7
        ],
        "end": [
          9,
          12
        ]
      }
    },
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

Diagnostic ranges use zero-based line and character positions.

Needs review: reportAssignmentType no longer reported

The base reports reportAssignmentType for this example; the PR does not. Is this change intended?

Reproduction and observed results

Create these files in an empty directory:

main.py

reveal_type(0)
import sys
if f"{sys.platform}" == sys.platform:
    value: int = "not an int"

pyrightconfig.json

{
  "include": [
    "main.py"
  ],
  "pythonVersion": "3.13",
  "pythonPlatform": "Linux",
  "typeCheckingMode": "basic"
}

From that directory, run each built Pyright revision:

node <pyright-cli-entrypoint> --outputjson -p .

Base e6d4bda989a07e384ed087ce73af5b6b4d69b64d

{
  "exit_code": 1,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "error",
      "rule": "reportAssignmentType",
      "message": "Type \"Literal['not an int']\" is not assignable to declared type \"int\"\n  \"Literal['not an int']\" is not assignable to \"int\"",
      "range": {
        "start": [
          3,
          17
        ],
        "end": [
          3,
          29
        ]
      }
    },
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

PR 2c3eef9fef402248c1cee0345dfd26a4f49ebaad

{
  "exit_code": 0,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

Diagnostic ranges use zero-based line and character positions.

Needs review: reportAssignmentType no longer reported

The base reports reportAssignmentType for this example; the PR does not. Is this change intended?

Reproduction and observed results

Create these files in an empty directory:

main.py

reveal_type(0)
import sys
if 3j != sys.version_info[0]:
    value: int = "not an int"

pyrightconfig.json

{
  "include": [
    "main.py"
  ],
  "pythonVersion": "3.13",
  "pythonPlatform": "Linux",
  "typeCheckingMode": "basic"
}

From that directory, run each built Pyright revision:

node <pyright-cli-entrypoint> --outputjson -p .

Base e6d4bda989a07e384ed087ce73af5b6b4d69b64d

{
  "exit_code": 1,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "error",
      "rule": "reportAssignmentType",
      "message": "Type \"Literal['not an int']\" is not assignable to declared type \"int\"\n  \"Literal['not an int']\" is not assignable to \"int\"",
      "range": {
        "start": [
          3,
          17
        ],
        "end": [
          3,
          29
        ]
      }
    },
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

PR 2c3eef9fef402248c1cee0345dfd26a4f49ebaad

{
  "exit_code": 0,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

Diagnostic ranges use zero-based line and character positions.

Needs review: reportAssignmentType no longer reported

The base reports reportAssignmentType for this example; the PR does not. Is this change intended?

Reproduction and observed results

Create these files in an empty directory:

main.py

reveal_type(0)
from typing import Literal
class Runtime:
    name: Literal["custom"] = "custom"
os = Runtime()
if "custom" == os.name:
    value: int = "not an int"

pyrightconfig.json

{
  "include": [
    "main.py"
  ],
  "pythonVersion": "3.13",
  "pythonPlatform": "Linux",
  "typeCheckingMode": "basic"
}

From that directory, run each built Pyright revision:

node <pyright-cli-entrypoint> --outputjson -p .

Base e6d4bda989a07e384ed087ce73af5b6b4d69b64d

{
  "exit_code": 1,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "error",
      "rule": "reportAssignmentType",
      "message": "Type \"Literal['not an int']\" is not assignable to declared type \"int\"\n  \"Literal['not an int']\" is not assignable to \"int\"",
      "range": {
        "start": [
          6,
          17
        ],
        "end": [
          6,
          29
        ]
      }
    },
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

PR 2c3eef9fef402248c1cee0345dfd26a4f49ebaad

{
  "exit_code": 0,
  "diagnostics": [
    {
      "file": "main.py",
      "severity": "information",
      "rule": null,
      "message": "Type of \"0\" is \"Literal[0]\"",
      "range": {
        "start": [
          0,
          12
        ],
        "end": [
          0,
          13
        ]
      }
    }
  ]
}

Diagnostic ranges use zero-based line and character positions.

[Peter Hayes (HTMLPETE)]

Thanks Heejae Chang (@heejaechang) for running the QA bot!

Here is the breakdown of the flagged cases:

1. (3, 13) < sys.version_info: Intended. When pythonVersion: "3.13", (3, 13) < (3, 13) evaluates statically to false. The body is dead code, which correctly suppresses unreachable assignment errors.
2. "custom" == os.name: Intended. Follows the same static evaluation rules as os.name == "custom", evaluating to false when target platform is Linux (posix), correctly pruning the dead branch.
3. b"linux" == sys.platform & f"{sys.platform}" == sys.platform: Fixed in 06b54fab. Added _isPlainStringList to ensure bytes tokens (StringTokenFlags.Bytes) and format strings (StringTokenFlags.Format) are never evaluated as static string matches against sys.platform / os.name.
4. 3j != sys.version_info[0]: Fixed in 06b54fab. Added !node.d.leftExpr.d.isImaginary guard to prevent imaginary numbers from being treated as integers in reversed version comparisons.

[crypt0lith]

This PR is a duplicate of #11929, and the author has opened duplicates of other PRs in the past (#11895). The author is encouraged to read the GitHub Acceptable Use Policy for spam and inauthentic activity.