Add index-compare-to-contains Linter

Summary

This PR introduces a new static analysis linter that detects strings.Index() and bytes.Index() comparisons that should be replaced with the more readable strings.Contains() or bytes.Contains() variants.

Motivation

Code patterns like strings.Index(s, sub) != -1 are valid but less idiomatic than strings.Contains(s, sub). This linter catches these patterns and suggests the more readable alternatives.

Patterns Detected

The linter reports the following patterns:

Positive Containment Checks

• strings.Index(s, sub) != -1 → strings.Contains(s, sub)
• strings.Index(s, sub) >= 0 → strings.Contains(s, sub)
• strings.Index(s, sub) > -1 → strings.Contains(s, sub)

Negative Containment Checks

• strings.Index(s, sub) == -1 → !strings.Contains(s, sub)
• strings.Index(s, sub) < 0 → !strings.Contains(s, sub)
• strings.Index(s, sub) <= -1 → !strings.Contains(s, sub)

Also Handles

• strings.LastIndex() / bytes.LastIndex() comparisons
• strings.IndexByte() / bytes.IndexByte() comparisons
• Yoda-order comparisons (e.g., -1 != strings.Index(...))
• Parenthesized expressions

Test Coverage

The linter includes comprehensive test cases covering:

• All comparison operators and patterns
• Both strings and bytes packages
• Normal and Yoda-order comparisons
• Edge cases and legitimate uses of Index() that should not be flagged

All tests pass:

✓ go test ./pkg/linters/indexcomparetocontains/...
✓ go build ./cmd/linters

Files Changed

1. pkg/linters/indexcomparetocontains/ - New linter package

   • indexcomparetocontains.go - Main linter implementation
   • indexcomparetocontains_test.go - Test suite
   • testdata/ - Test fixtures

2. pkg/linters/README.md - Added linter documentation

3. pkg/linters/registry.go - Registered the new analyzer

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Generated by Linter Miner · copilot · mai10 · 168.3 AIC · ⊞ 6.6K · ◷

• expires on Oct 12, 2026, 9:47 AM UTC-08:00