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eq(Int, $T2)
eq($T1, Int)
eq($T3, Int)
eq(Int, $T2)
Slide 71
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&YBNQMFPG*OGFSFODF
eq($T1, $T2)
call(($T3) -> $T3, Int, $T2)
eq($T1, $T2)
eq($T3, Int)
eq($T3, $T2)
eq($T1, $T2)
eq($T3, Int)
eq(Int, $T2)
eq($T1, Int)
eq($T3, Int)
eq(Int, $T2)
Slide 72
Slide 72 text
&YBNQMFPG*OGFSFODF
eq($T1, $T2)
call(($T3) -> $T3, Int, $T2)
eq($T1, $T2)
eq($T3, Int)
eq($T3, $T2)
eq($T1, $T2)
eq($T3, Int)
eq(Int, $T2)
eq($T1, Int)
eq($T3, Int)
eq(Int, $T2)
Slide 73
Slide 73 text
&YBNQMFPG*OGFSFODF
eq($T1, $T2)
call(($T3) -> $T3, Int, $T2)
eq($T1, $T2)
eq($T3, Int)
eq($T3, $T2)
eq($T1, $T2)
eq($T3, Int)
eq(Int, $T2)
eq($T1, Int)
eq($T3, Int)
eq(Int, $T2)
Slide 74
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
Slide 76
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
Slide 77
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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eq($T3, Int)
7FSJGJDBUJPOPG*OGFSFODF3FTVMUT
eq($T1, Int)
eq(Int, $T2)
WBSEFDMB
DBMM
EFDMSFGJE EFDMSFGJ
$T1
$T2
($T3) -> $T3 Int
Int
Int
(Int) -> Int
func id(_ x: X) -> X
func main(i: Int) {
let a = id(i)
}
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$PNQMFUJPOPG5ZQF*OGFSFODF
w "MMUZQFWBSJBCMFTUZQFTBSFEFUFSNJOFEˠ5ZQFJOGFSFODFTVDDFTTGVM
w $POUSBEJDUJPOPDDVSTˠ5IFDPEFJTJODPSSFDU
w 6OLOPXOUZQFWBSJBCMFTSFNBJO
CVUJOGFSFODFDBOOPUQSPDFFEˠ5IF
DPEFTUZQFJTBNCJHVPVT
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#JEJSFDUJPOBMJUZ
func readInt() -> Int
func read() -> X
func main() {
let a = readInt()
let b: Int = read()
}
eq($T1, $T2)
eq(Int, $T3)
call(() -> $T4, $T4, $T3)
call(() -> Int, (), $T2)
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#JEJSFDUJPOBMJUZ
func readInt() -> Int
func read() -> X
func main() {
let a = readInt()
let b: Int = read()
}
eq($T1, $T2)
eq(Int, $T3)
call(() -> $T4, $T4, $T3)
call(() -> Int, (), $T2)
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#JEJSFDUJPOBMJUZ
func readInt() -> Int
func read() -> X
func main() {
let a = readInt()
let b: Int = read()
}
eq($T1, $T2)
eq(Int, $T3)
call(() -> $T4, $T4, $T3)
call(() -> Int, (), $T2)
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#JEJSFDUJPOBMJUZ
func readInt() -> Int
func read() -> X
func main() {
let a = readInt()
let b: Int = read()
}
eq($T1, $T2)
eq(Int, $T3)
call(() -> $T4, $T4, $T3)
call(() -> Int, (), $T2)
Slide 90
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&YUFOTJPOTGPS4XJGU
Slide 91
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*OUSPEVDUJPOPGDPOWFSTJPOSFMBUJPOTBOENPEJGJDBUJPOPGBTTJHONFOU
TUBUFNFOUDPOTUSBJOUT
w 4XJGUIBTJNQMJDJUUZQFDPOWFSTJPOT
func main(i: Int) {
let a: Int? = i
}
eq(Int?, Int) conv(Int, Int?)
❌ ✅
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4JNQMJGJDBUJPOPG$POWFSTJPO$POTUSBJOUT
conv((A) -> B, (C) -> D)
conv(B, D)
conv(C, A)
1BSBNFUFST 🙃DPOUSBWBSJBODF
3FUVSOWBMVFT 🙂DPWBSJBODF
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.PEJGJDBUJPOPGTJNQMJGJDBUJPOPGGVODUJPODBMMJOHDPOTUSBJOUT
call((A) -> B, C, D)
eq(B, D)
conv(C, A)
1BSBNFUFST 🙃
3FUVSOWBMVFT
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1SPCMFNPG$POWFSTJPO$POTUSBJOUT
func main(i: Int) {
let a = i
}
conv(Int, $T1)
🤷
eq($T1, Int)
eq($T1, Int?)
eq($T1, Any)
0,
0,
0,
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(FOFSBUJPOBOE"UUFNQUPG6OJGJDBUJPO$BOEJEBUFT
conv(Int, $T1) eq($T1, Int)
QPTTJCJMF
func main(i: Int) {
let a = i
}
func main(i: Int) {
let a: Int = i
}
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&YBNQMFPG$BOEJEBUF4FBSDI
conv($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
conv(Int, $T1) eq($T1, Int)
eq($T1, Int?)
eq($T2, Int?)
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&YBNQMFPG4FBSDI1MBO
4UBSU
5*OU
5*OU
5*OU
5*OU
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4UBSU
5*OU
5*OU
5*OU
5*OU
conv($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, $T2)
eq(Int, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, Int)
eq(Int, $T2)
eq($T1, Int)
Slide 99
Slide 99 text
4UBSU
5*OU
5*OU
5*OU
5*OU
conv($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, $T2)
eq(Int, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, Int)
eq(Int, $T2)
eq($T1, Int)
Slide 100
Slide 100 text
4UBSU
5*OU
5*OU
5*OU
5*OU
conv($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, $T2)
eq(Int, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, Int)
eq(Int, $T2)
eq($T1, Int)
Slide 101
Slide 101 text
4UBSU
5*OU
5*OU
5*OU
5*OU
conv($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, $T2)
eq(Int, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, Int)
eq(Int, $T2)
eq($T1, Int)
Slide 102
Slide 102 text
4UBSU
5*OU
5*OU
5*OU
5*OU
conv($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, $T2)
eq(Int, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, Int)
eq(Int, $T2)
eq($T1, Int)
Slide 103
Slide 103 text
4UBSU
5*OU
5*OU
5*OU
5*OU
conv($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, $T2)
eq(Int, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, Int)
eq(Int, $T2)
eq($T1, Int)
Slide 104
Slide 104 text
4UBSU
5*OU
5*OU
5*OU
5*OU
conv($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, $T2)
eq(Int, $T2)
eq($T1, Int)
conv(Int, Int?)
conv(Int?, Int)
eq(Int, $T2)
eq($T1, Int)
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Slide 105 text
4UBSU
5*OU
5*OU
5*OU
5*OU
❌
eq($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
conv(Int, $T1)
eq($T1, Int?)
conv(Int?, $T2)
eq(Int?, $T2)
conv(Int, Int?)
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conv(Int?, Int?)
eq(Int?, $T2)
conv(Int, Int?)
Slide 106
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4UBSU
5*OU
5*OU
5*OU
5*OU
❌
eq($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
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eq(Int?, $T2)
conv(Int, Int?)
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conv(Int?, Int?)
eq(Int?, $T2)
conv(Int, Int?)
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4UBSU
5*OU
5*OU
5*OU
5*OU
❌
eq($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
conv(Int, $T1)
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eq(Int?, $T2)
conv(Int, Int?)
eq($T1, Int?)
conv(Int?, Int?)
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conv(Int, Int?)
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4UBSU
5*OU
5*OU
5*OU
5*OU
❌
eq($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
conv(Int, $T1)
eq($T1, Int?)
conv(Int?, $T2)
eq(Int?, $T2)
conv(Int, Int?)
eq($T1, Int?)
conv(Int?, Int?)
eq(Int?, $T2)
conv(Int, Int?)
Slide 109
Slide 109 text
4UBSU
5*OU
5*OU
5*OU
5*OU
❌
eq($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
conv(Int, $T1)
eq($T1, Int?)
conv(Int?, $T2)
eq(Int?, $T2)
conv(Int, Int?)
eq($T1, Int?)
conv(Int?, Int?)
eq(Int?, $T2)
conv(Int, Int?)
Slide 110
Slide 110 text
4UBSU
5*OU
5*OU
5*OU
5*OU
❌
eq($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
conv(Int, $T1)
eq($T1, Int?)
conv(Int?, $T2)
eq(Int?, $T2)
conv(Int, Int?)
eq($T1, Int?)
conv(Int?, Int?)
eq(Int?, $T2)
conv(Int, Int?)
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4UBSU
5*OU
5*OU
5*OU
5*OU
❌
eq($T1, Int?)
conv(Int?, $T2)
eq($T1, $T2)
conv(Int, $T1)
eq($T1, Int?)
conv(Int?, $T2)
eq(Int?, $T2)
conv(Int, Int?)
eq($T1, Int?)
conv(Int?, Int?)
eq(Int?, $T2)
conv(Int, Int?)
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)BOEMJOH0WFSMPBET
func foo() -> Bool
func foo() -> Int
func foo() -> String
func main(i: Int) {
let a: Int = foo()
}
call($T1, (), Int)
eq($T1, () -> Bool)
eq($T1, () -> Int)
eq($T1, () -> String)
QPTTJCJMFY
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)BOEMJOH0WFSMPBET
func foo() -> Bool
func foo() -> Int
func foo() -> String
func main(i: Int) {
let a: Int = foo()
}
call($T1, (), Int)
eq($T1, () -> Bool)
eq($T1, () -> Int)
eq($T1, () -> String)
QPTTJCJMFY
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)BOEMJOH0WFSMPBET
func foo() -> Bool
func foo() -> Int
func foo() -> String
func main(i: Int) {
let a: Int = foo()
}
call($T1, (), Int)
eq($T1, () -> Bool)
eq($T1, () -> Int)
eq($T1, () -> String)
QPTTJCJMFY
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)BOEMJOH0WFSMPBET
func foo() -> Bool
func foo() -> Int
func foo() -> String
func main(i: Int) {
let a: Int = foo()
}
call($T1, (), Int)
eq($T1, () -> Bool)
eq($T1, () -> Int)
eq($T1, () -> String)
QPTTJCJMFY
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"UUFNQUTBOE$PNQVUBUJPOBM$PNQMFYJUZ
w 5IFNFDIBOJTNPGlBUUFNQUDBOEJEBUFTzIBTUIFQPUFOUJBMUPFYQMPEF
JODPNQVUBUJPOBMDPNQMFYJUZ
💣
code.swift:11:9: error: the compiler is unable to type-check this
expression in reasonable time; try breaking up the expression
into distinct sub-expressions
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-FBSOJOHGSPNUIF$PNQJMFS
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.BLJOHUIF$PNQJMFS0VUQVUUIF0QFSBUJPOTPG5ZQF*OGFSFODF
$ swiftc -Xfrontend -debug-constraints code.swift
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
0VUQVUFYDFFEJOHMJOFT🤯
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*OGFSFODFQSPDFTT
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODFQSPDFTT
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODFQSPDFTT
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODFQSPDFTT
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODFQSPDFTT
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODFQSPDFTT
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODFQSPDFTT
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODFQSPDFTT
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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$ swiftc -Xfrontend -debug-constraints code.swift
---Constraint solving at [code.swift:1:21 - line:1:21]---
(…)
---Constraint solving at [code.swift:2:22 - line:2:22]---
(…)
---Constraint solving at [code.swift:5:9 - line:5:22]---
(…)
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
0VUQVUGPSUIF&OUJSF$PEF
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$ swiftc -Xfrontend -debug-constraints code.swift
---Constraint solving at [code.swift:1:21 - line:1:21]---
(…)
---Constraint solving at [code.swift:2:22 - line:2:22]---
(…)
---Constraint solving at [code.swift:5:9 - line:5:22]---
(…)
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
0VUQVUGPSUIF&OUJSF$PEF
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$ swiftc -Xfrontend -debug-constraints code.swift
---Constraint solving at [code.swift:1:21 - line:1:21]---
(…)
---Constraint solving at [code.swift:2:22 - line:2:22]---
(…)
---Constraint solving at [code.swift:5:9 - line:5:22]---
(…)
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
0VUQVUGPSUIF&OUJSF$PEF
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$ swiftc -Xfrontend -debug-constraints code.swift
---Constraint solving at [code.swift:1:21 - line:1:21]---
(…)
---Constraint solving at [code.swift:2:22 - line:2:22]---
(…)
---Constraint solving at [code.swift:5:9 - line:5:22]---
(…)
func foo() -> Int { 0 }
func foo() -> Bool { true }
func main() {
let a: Int = foo()
}
0VUQVUGPSUIF&OUJSF$PEF
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0VUQVUGPS*OEJWJEVBM*OGFSFODFT
---Constraint solving at [code.swift:5:9 - line:5:22]---
---Initial constraints for the given expression---
(Initial State of the AST)
(Initial State of the Constraints)
(Inference Process)
---Solution---
(Solution)
---Type-checked expression---
(Typed AST)
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*OJUJBM4UBUFPGUIF"45
---Initial constraints for the given expression—
(call_expr type='$T1'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:22]
isolationCrossing=none
(overloaded_decl_ref_expr type='$T0'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:18]
name=foo number_of_decls=2 function_ref=single
decls=[
code.(file).foo()@code.swift:1:6,
code.(file).foo()@code.swift:2:6])
(argument_list))
let a: Int = foo()
DBMM
EFDMSFGJE
$T0
$T1
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*OJUJBM4UBUFPGUIF"45
---Initial constraints for the given expression—
(call_expr type='$T1'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:22]
isolationCrossing=none
(overloaded_decl_ref_expr type='$T0'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:18]
name=foo number_of_decls=2 function_ref=single
decls=[
code.(file).foo()@code.swift:1:6,
code.(file).foo()@code.swift:2:6])
(argument_list))
let a: Int = foo()
DBMM
EFDMSFGJE
$T0
$T1
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*OJUJBM4UBUFPGUIF"45
---Initial constraints for the given expression—
(call_expr type='$T1'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:22]
isolationCrossing=none
(overloaded_decl_ref_expr type='$T0'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:18]
name=foo number_of_decls=2 function_ref=single
decls=[
code.(file).foo()@code.swift:1:6,
code.(file).foo()@code.swift:2:6])
(argument_list))
let a: Int = foo()
DBMM
EFDMSFGJE
$T0
$T1
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*OJUJBM4UBUFPGUIF"45
---Initial constraints for the given expression—
(call_expr type='$T1'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:22]
isolationCrossing=none
(overloaded_decl_ref_expr type='$T0'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:18]
name=foo number_of_decls=2 function_ref=single
decls=[
code.(file).foo()@code.swift:1:6,
code.(file).foo()@code.swift:2:6])
(argument_list))
let a: Int = foo()
DBMM
EFDMSFGJE
$T0
$T1
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
Slide 139
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
Slide 142
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
Slide 143
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
Slide 145
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
Slide 146
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*OJUJBM4UBUFPGUIF$POTUSBJOUT
Score:
Contextual Type: Int at [code.swift:5:12 - line:5:12]
Type Variables:
$T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings:
] @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes
of) Int] @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern match →
pattern match → named pattern decl]
Inactive Constraints:
disjunction @ locator@0x11b81ac00 [[email protected]:5:18]:
> $T0 bound to decl code.(file).foo()@code.swift:1:6 : () -> Int
> $T0 bound to decl code.(file).foo()@code.swift:2:6 : () -> Bool
() -> $T1 applicable fn $T0 @ locator@0x11b81ae30 [[email protected]:5:18 → apply function]
$T1 conv Int @ locator@0x11b81aec8 [[email protected]:5:18 → contextual type]
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*OGFSFODF1SPDFTT
(attempting type variable binding $T1 := Int
...
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00
[[email protected]:5:18]
...
(found solution: )
)
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00
[[email protected]:5:18]
...
(outcome: error)
)
)
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODF1SPDFTT
(attempting type variable binding $T1 := Int
...
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00
[[email protected]:5:18]
...
(found solution: )
)
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00
[[email protected]:5:18]
...
(outcome: error)
)
)
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
Slide 149
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*OGFSFODF1SPDFTT
(attempting type variable binding $T1 := Int
...
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00
[[email protected]:5:18]
...
(found solution: )
)
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00
[[email protected]:5:18]
...
(outcome: error)
)
)
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODF1SPDFTT
(attempting type variable binding $T1 := Int
...
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00
[[email protected]:5:18]
...
(found solution: )
)
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00
[[email protected]:5:18]
...
(outcome: error)
)
)
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODF1SPDFTT
(attempting type variable binding $T1 := Int
...
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00
[[email protected]:5:18]
...
(found solution: )
)
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00
[[email protected]:5:18]
...
(outcome: error)
)
)
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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*OGFSFODF1SPDFTT
(attempting type variable binding $T1 := Int
...
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00
[[email protected]:5:18]
...
(found solution: )
)
(attempting disjunction choice $T0 bound to decl code.
(file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00
[[email protected]:5:18]
...
(outcome: error)
)
)
4UBSU
5*OU
5
*OU 5
#PPM
4VDDFTT 'BJMVSF
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4PMVUJPO
---Solution---
Fixed score:
Type variables:
$T0 as () -> Int @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 as Int @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern
match → pattern match → named pattern decl]
Overload choices:
locator@0x11b81ac00 [[email protected]:5:18] with code.
(file).foo()@code.swift:1:6 as foo: () -> Int
Trailing closure matching:
locator@0x11b81afe8 [[email protected]:5:18 → apply argument]: forward
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4PMVUJPO
---Solution---
Fixed score:
Type variables:
$T0 as () -> Int @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 as Int @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern
match → pattern match → named pattern decl]
Overload choices:
locator@0x11b81ac00 [[email protected]:5:18] with code.
(file).foo()@code.swift:1:6 as foo: () -> Int
Trailing closure matching:
locator@0x11b81afe8 [[email protected]:5:18 → apply argument]: forward
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4PMVUJPO
---Solution---
Fixed score:
Type variables:
$T0 as () -> Int @ locator@0x11b81ac00 [[email protected]:5:18]
$T1 as Int @ locator@0x11b81adb0 [[email protected]:5:18 → function result]
$T2 as Int @ locator@0x11b81aef0 [[email protected]:5:18 → contextual type → pattern
match → pattern match → named pattern decl]
Overload choices:
locator@0x11b81ac00 [[email protected]:5:18] with code.
(file).foo()@code.swift:1:6 as foo: () -> Int
Trailing closure matching:
locator@0x11b81afe8 [[email protected]:5:18 → apply argument]: forward
Slide 156
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5ZQFE"45
---Type-checked expression---
(call_expr type=‘Int'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:22]
isolationCrossing=none
(declref_expr type='() -> Int’
location=code.swift:5:18
range=[code.swift:5:18 - line:5:18]
decl=code.(file).foo()@code.swift:1:6
function_ref=single)
(argument_list))
let a: Int = foo()
DBMM
EFDMSFGJE
() -> Int
Int
Slide 157
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5ZQFE"45
---Type-checked expression---
(call_expr type=‘Int'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:22]
isolationCrossing=none
(declref_expr type='() -> Int’
location=code.swift:5:18
range=[code.swift:5:18 - line:5:18]
decl=code.(file).foo()@code.swift:1:6
function_ref=single)
(argument_list))
let a: Int = foo()
DBMM
EFDMSFGJE
() -> Int
Int
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5ZQFE"45
---Type-checked expression---
(call_expr type=‘Int'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:22]
isolationCrossing=none
(declref_expr type='() -> Int’
location=code.swift:5:18
range=[code.swift:5:18 - line:5:18]
decl=code.(file).foo()@code.swift:1:6
function_ref=single)
(argument_list))
let a: Int = foo()
DBMM
EFDMSFGJE
() -> Int
Int
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5ZQFE"45
---Type-checked expression---
(call_expr type=‘Int'
location=code.swift:5:18
range=[code.swift:5:18 - line:5:22]
isolationCrossing=none
(declref_expr type='() -> Int’
location=code.swift:5:18
range=[code.swift:5:18 - line:5:18]
decl=code.(file).foo()@code.swift:1:6
function_ref=single)
(argument_list))
let a: Int = foo()
DBMM
EFDMSFGJE
() -> Int
Int
Slide 160
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3FDBQ
w 5IFCBTJDTPGUZQFJOGFSFODFBSFVOJ
fi
DBUJPOBOETJNQMJ
fi
DBUJPOPG
DPOTUSBJOUT
w 4XJGUFYUFOETJUCZBEEJOHTFBSDIUPUIFQSPDFTT
w 8FDBOVOEFSTUBOEJUTPQFSBUJPOTCZMPPLJOHBUUIFDPNQJMFSTPVUQVU
Slide 161
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/FYU4UFQT
w JNQMFNFOUJOHUZQFJOGFSFODF
https://stackoverflow.com/questions/415532/implementing-type-
inference
w 5ZQF$IFDLFS%FTJHOBOE*NQMFNFOUBUJPO
https://github.com/apple/swift/blob/main/docs/TypeChecker.md
w 4XJGU5ZQF*OGFSFODF)BOET0O
https://github.com/omochi/SwiftTypeInferenceHandsOn
w $PNQJMJOH4XJGUHFOFSJDT
1BSU*
https://forums.swift.org/t/compiling-swift-generics-part-i/60898