For history buffs: https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_system https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_sy... was invented

For history buffs: https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_system https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_sy... was invented in 1969 (and rediscovered my Milner in 1978). AFAIK, that was the basis of type inference in many of the non-mainstream languages before they branched off into their own more powerful type systems.