Bug: `explicit_self` false positive with string interpolation

[jffmrk]

New Issue Checklist

• I've Updated SwiftLint to the latest version.
• I've searched for existing GitHub issues.

Bug Description

The explicit_self analyzer rule reports a violation (“Instance variables and functions should be explicitly accessed with self.”) even when the member is already accessed with self. inside string interpolation \(...) (and the same pattern with raw-string interpolation \#(...)).

Expected: No violation; self is explicit.

Actual: explicit_self reports a violation (false positive).

explicit_self only runs with swiftlint analyze (compiler invocations required), not swiftlint lint.

Minimal example:

class StringInterpolation {
    let foo = "foo"

    var description: String {
        return "StringInterpolation{foo: \(self.foo)}"
    }

    var rawStringLiteral: String {
        return #"StringInterpolation{foo: \#(self.foo)} using "raw" string literals."#
    }
}

Full repro (Swift package, xcodebuild log + analyze): https://github.com/jffmrk/swiftlint-explicit-self-string-interpolation

Example command output:

$ swiftlint analyze --compiler-log-path xcodebuild.log
Analyzing 'StringInterpolation.swift' (1/1)
/Users/jmark/src/github/swiftlint-explicit-self-string-interpolation/Sources/ExplicitSelfStringInterpolationBug/StringInterpolation.swift:5:43: error: Explicit Self Violation: Instance variables and functions should be explicitly accessed with 'self.' (explicit_self)
/Users/jmark/src/github/swiftlint-explicit-self-string-interpolation/Sources/ExplicitSelfStringInterpolationBug/StringInterpolation.swift:9:45: error: Explicit Self Violation: Instance variables and functions should be explicitly accessed with 'self.' (explicit_self)

(Line/column may vary slightly by Swift/Xcode version.)

Environment

• SwiftLint version (run swiftlint version to be sure): 0.63.2
• Xcode version (run xcodebuild -version to be sure): Xcode 26.4 (Build version 17E192)
• Installation method used (Homebrew, CocoaPods, building from source, etc): Homebrew (/opt/homebrew/bin/swiftlint)
• Configuration file:

analyzer_rules:
  - explicit_self

explicit_self:
  severity: error

Are you using nested configurations? No — single .swiftlint.yml at the repository root.

[jffmrk]

We just enabled explicit_self on our repo, and a lot of false positives showed up under string interpolation.

PR with a fix:
#6610