How to reproduce:
1. Open the user’s attached “Shader Graph BI Tutorial.zip” project
2. Open any Shader Graph
3. Create a “Custom Function” Node
4. In the Graph Inspector, add an Output
5. Change the name
6. Change the Type to “String”
7. Add “New = 1;” to “Body”
8. Observe the Node

Expected result: No error
Actual result: “Validation: Source file does not exist. A valid .hlsl, .cginc, or .cg file must be referenced at line 0“ error appears

Reproducible with: 12.0.0 (2021.2.0a16), 12.1.9 (2021.2.19f1), 12.1.11 (2021.3.26f1), 14.0.7 (2022.2.21f1), 15.0.5 (2023.1.0b18), 16.0.1 (2023.2.0a16)
Not reproducible with: 10.10.1 (2020.3.48f1), 12.0.0 (2021.2.0a15)

Reproduced on: macOS 13.2.1 (Intel)

Note: Not reproducible if setting type to “string” before adding output