Invalid YAML parses successfully: indentation changed after scalar value

[Braydon Kains]

Describe the bug
The following YAML is invalid:

a: 'b'
  b: 1

It is invalid because the indentation level has changed after a scalar value, which doesn't make sense.

To Reproduce
https://go.dev/play/p/WkfZUGjlNY6

Expected behavior
This yaml should be rejected with an error.

Screenshots
If applicable, add screenshots to help explain your problem.

Version Variables

• Go version: 1.21
• go-yaml's Version: v1.11.2

Additional context
In the playground, I show that yaml.v3 correctly rejects the invalid yaml.

[Braydon Kains]

Very likely #358 is related

[Masaaki Goshima]

Thank you for your reporting. I'll try to fix this problem.