How to reproduce:
1. Open Unity
2. Create a new project
3. Import tester-submitted shader (Test.shader)
4. Inspect shader syntax error pointing at line 102 (unexpected ';')
5. Switch to alternative shadow rendering mode at line 74
6. Notice shader syntax error disappear at line 102

Expected result: Unity compiles both shadow rendering modes correctly.
Actual result: Unity does not compile 'Forward Add' shadow rendering mode and complains about syntax errors

Reproducible with - 2018.1.0a1, 2018.1.0b6
Not reproducible with - 5.6.5p1, 2017.1.3p1, 2017.2.1p3, 2017.3.1p1

Verified in: 2018.2.0a5