Type inference impact on Swift 2.2 code compile time.

CurryBench.swift

// CurryLight.swift

func curry<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, T23, T24, T25, U>(f: (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, T23, T24, T25) -> U) -> (T1) -> (T2) -> (T3) -> (T4) -> (T5) -> (T6) -> (T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U {
    return { (x1: T1) -> (T2) -> (T3) -> (T4) -> (T5) -> (T6) -> (T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x2: T2) -> (T3) -> (T4) -> (T5) -> (T6) -> (T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x3: T3) -> (T4) -> (T5) -> (T6) -> (T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x4: T4) -> (T5) -> (T6) -> (T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x5: T5) -> (T6) -> (T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x6: T6) -> (T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x7: T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x8: T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x9: T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x10: T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x11: T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x12: T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x13: T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x14: T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x15: T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x16: T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x17: T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x18: T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x19: T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x20: T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x21: T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U in { (x22: T22) -> (T23) -> (T24) -> (T25) -> U in { (x23: T23) -> (T24) -> (T25) -> U in { (x24: T24) -> (T25) -> U in { (x25: T25) -> U in f(x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25) } } } } } } } } } } } } } } } } } } } } } } } } }
}

// CurryHard.swift

func curry<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, T23, T24, T25, U>(f: (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, T23, T24, T25) -> U) -> (T1) -> (T2) -> (T3) -> (T4) -> (T5) -> (T6) -> (T7) -> (T8) -> (T9) -> (T10) -> (T11) -> (T12) -> (T13) -> (T14) -> (T15) -> (T16) -> (T17) -> (T18) -> (T19) -> (T20) -> (T21) -> (T22) -> (T23) -> (T24) -> (T25) -> U {
    return { x1 in { x2 in { x3 in { x4 in { x5 in { x6 in { x7 in { x8 in { x9 in { x10 in { x11 in { x12 in { x13 in { x14 in { x15 in { x16 in { x17 in { x18 in { x19 in { x20 in { x21 in { x22 in { x23 in { x24 in { x25 in f(x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25) } } } } } } } } } } } } } } } } } } } } } } } } }
}

/*
$ time swiftc CurryLight.swift && time swiftc CurryHard.swift

real	0m3.648s
user	0m3.617s
sys	0m0.021s

real	8m47.694s
user	8m28.325s
sys	0m18.097s

$ swift --version
Apple Swift version 2.2 (swiftlang-703.0.18.8 clang-703.0.31)
Target: x86_64-apple-macosx10.9
*/

See also Generating curry function in Swift 2.2.