How to reproduce:
1. Create a new project
2. Import the Shader Graph package from the Package Manager
3. In the Project window create any new Shader Graph (for example, Unlit Graph)
4. Open the newly created graph
5. Create a new Custom Function Node
6. Click the cogwheel icon in the newly created Node
7. Add an input 'a' and an output 'b' of type Vector 1 to the Custom Function
8. Change the Function Type to 'String'
9. Enter a Function Name that would have a whitespace symbol (for example, 'My Function' or 'MyFunction ')
10. Enter the function body as 'b = a;'

Expected results: the whitespace gets stripped and Custom Function compiles successfully or an informative error is thrown
Actual results: the Custom Function fails to compile giving the following error: syntax error: unexpected token '_float'

Reproducible with: 7.3.1 (2019.4.2f1), 8.1.0 (2020.1.0b13, 2020.2.0a15), 9.0.0-preview.14 (2020.2.0a15)
Could not test with: 2018.4.24f1 (could not create a Custom Function Node)

Notes:
The error message is unclear because the user does not write '_float' which is added to the end of the function name