Swiftの型推論を学ぼう | Let's Learn About Type Inference in Swift

try! Swift Tokyo 2024 で発表しました。

スクリプトはこちら
https://speakerdeck.com/omochi/sukuriputo-swiftnoxing-tui-lun-woxue-bou

Transcript

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47. 6OJGJDBUJPO w 'JOE
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48. 6OJGJDBUJPO w 'JOE
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49. 6OJGJDBUJPO w 'JOE
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50. 6OJGJDBUJPO w 'JOE
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51. 4JNQMJGJDBUJPO
    PG
    FRVBM
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52. 4JNQMJGJDBUJPO
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53. 4JNQMJGJDBUJPO
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54. 4JNQMJGJDBUJPO
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55. 5IF
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56. 5IF
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57. 5IF
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58. 5IF
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59. 5IF
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60. 5IF
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61. 5IF
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62. 5IF
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    BOE
    TJNQMJGJDBUJPO call($T1, $T2, $T3) eq($T1, (Int) -> Bool) call((Int) -> Bool, $T2, $T3) eq($T1, (Int) -> Bool) eq(Int, $T2) eq($T1, (Int) -> Bool) eq(Bool, $T3)
63. 5IF
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64. &YBNQMF
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65. &YBNQMF
    PG
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66. &YBNQMF
    PG
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67. &YBNQMF
    PG
    *OGFSFODF eq($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, $T2)
68. &YBNQMF
    PG
    *OGFSFODF eq($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, $T2)
69. &YBNQMF
    PG
    *OGFSFODF eq($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, $T2)
70. &YBNQMF
    PG
    *OGFSFODF eq($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, $T2)
71. &YBNQMF
    PG
    *OGFSFODF eq($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, $T2)
72. &YBNQMF
    PG
    *OGFSFODF eq($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, $T2)
73. &YBNQMF
    PG
    *OGFSFODF eq($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, $T2)
74. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
75. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
76. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
77. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
78. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
79. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
80. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
81. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
82. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
83. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
84. eq($T3, Int) 7FSJGJDBUJPO
    PG
    *OGFSFODF
    3FTVMUT eq($T1, Int) eq(Int, $T2) WBS
    EFDM
    B DBMM EFDM
    SFG
    JE EFDM
    SFG
    J $T1 $T2 ($T3) -> $T3 Int Int Int (Int) -> Int func id<X>(_ x: X) -> X func main(i: Int) { let a = id(i) }
85. $PNQMFUJPO
    PG
    5ZQF
    *OGFSFODF w "MM
    UZQF
    WBSJBCMFT
    UZQFT
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86. #JEJSFDUJPOBMJUZ func readInt() -> Int func read<X>() -> X func main() { let a = readInt() let b: Int = read() } eq($T1, $T2) eq(Int, $T3) call(() -> $T4, $T4, $T3) call(() -> Int, (), $T2)
87. #JEJSFDUJPOBMJUZ func readInt() -> Int func read<X>() -> X func main() { let a = readInt() let b: Int = read() } eq($T1, $T2) eq(Int, $T3) call(() -> $T4, $T4, $T3) call(() -> Int, (), $T2)
88. #JEJSFDUJPOBMJUZ func readInt() -> Int func read<X>() -> X func main() { let a = readInt() let b: Int = read() } eq($T1, $T2) eq(Int, $T3) call(() -> $T4, $T4, $T3) call(() -> Int, (), $T2)
89. #JEJSFDUJPOBMJUZ func readInt() -> Int func read<X>() -> X func main() { let a = readInt() let b: Int = read() } eq($T1, $T2) eq(Int, $T3) call(() -> $T4, $T4, $T3) call(() -> Int, (), $T2)
90. &YUFOTJPOT
    GPS
    4XJGU
91. *OUSPEVDUJPO
    PG
    DPOWFSTJPO
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    DPOTUSBJOUT w 4XJGU
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92. 4JNQMJGJDBUJPO
    PG
    $POWFSTJPO
    $POTUSBJOUT conv((A) -> B, (C) -> D) conv(B, D) conv(C, A) 1BSBNFUFST
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93. .PEJGJDBUJPO
    PG
    TJNQMJGJDBUJPO
    PG
    GVODUJPO
    DBMMJOH
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94. 1SPCMFN
    PG
    $POWFSTJPO
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95. (FOFSBUJPO
    BOE
    "UUFNQU
    PG
    6OJGJDBUJPO
    $BOEJEBUFT conv(Int, $T1) eq($T1, Int) QPTTJCJMF func main(i: Int) { let a = i } func main(i: Int) { let a: Int = i }
96. &YBNQMF
    PG
    $BOEJEBUF
    4FBSDI conv($T1, Int?) conv(Int?, $T2) eq($T1, $T2) conv(Int, $T1) eq($T1, Int) eq($T1, Int?) eq($T2, Int?)
97. &YBNQMF
    PG
    4FBSDI
    1MBO 4UBSU 5
    
    *OU 5
    
    *OU 5
    
    *OU 5
    
    *OU
98. 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)
99. 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)
100. 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)
101. 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)
102. 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)
103. 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)
104. 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)
105. 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?)
106. 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?)
107. 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?)
108. 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?)
109. 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?)
110. 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?)
111. 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?, $T2) conv(Int, Int?)
112. )BOEMJOH
     0WFSMPBET func foo() -> Bool func foo() -> Int func foo() -> String func main(i: Int) { let a: Int = foo() } call($T1, (), Int) eq($T1, () -> Bool) eq($T1, () -> Int) eq($T1, () -> String) QPTTJCJMF
     Y
113. )BOEMJOH
     0WFSMPBET func foo() -> Bool func foo() -> Int func foo() -> String func main(i: Int) { let a: Int = foo() } call($T1, (), Int) eq($T1, () -> Bool) eq($T1, () -> Int) eq($T1, () -> String) QPTTJCJMF
     Y
114. )BOEMJOH
     0WFSMPBET func foo() -> Bool func foo() -> Int func foo() -> String func main(i: Int) { let a: Int = foo() } call($T1, (), Int) eq($T1, () -> Bool) eq($T1, () -> Int) eq($T1, () -> String) QPTTJCJMF
     Y
115. )BOEMJOH
     0WFSMPBET func foo() -> Bool func foo() -> Int func foo() -> String func main(i: Int) { let a: Int = foo() } call($T1, (), Int) eq($T1, () -> Bool) eq($T1, () -> Int) eq($T1, () -> String) QPTTJCJMF
     Y
116. "UUFNQUT
     BOE
     $PNQVUBUJPOBM
     $PNQMFYJUZ w 5IF
     NFDIBOJTN
     PG
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     DBOEJEBUFTz
     IBT
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     FYQMPEF
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     DPNQVUBUJPOBM
     DPNQMFYJUZ 💣 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
117. -FBSOJOH
     GSPN
     UIF
     $PNQJMFS
118. .BLJOH
     UIF
     $PNQJMFS
     0VUQVU
     UIF
     0QFSBUJPOT
     PG
     5ZQF
     *OGFSFODF $ swiftc -Xfrontend -debug-constraints code.swift func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 0VUQVU
     FYDFFEJOH
     
     MJOFT
     🤯
119. *OGFSFODF
     QSPDFTT func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
120. *OGFSFODF
     QSPDFTT func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
121. *OGFSFODF
     QSPDFTT func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
122. *OGFSFODF
     QSPDFTT func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
123. *OGFSFODF
     QSPDFTT func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
124. *OGFSFODF
     QSPDFTT func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
125. *OGFSFODF
     QSPDFTT func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
126. *OGFSFODF
     QSPDFTT func foo() -> Int { 0 } func foo() -> Bool { true } func main() { let a: Int = foo() } 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
127. $ 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() } 0VUQVU
     GPS
     UIF
     &OUJSF
     $PEF
128. $ 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() } 0VUQVU
     GPS
     UIF
     &OUJSF
     $PEF
129. $ 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() } 0VUQVU
     GPS
     UIF
     &OUJSF
     $PEF
130. $ 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() } 0VUQVU
     GPS
     UIF
     &OUJSF
     $PEF
131. 0VUQVU
     GPS
     *OEJWJEVBM
     *OGFSFODFT ---Constraint solving at [code.swift:5:9 - line:5:22]--- ---Initial constraints for the given expression--- (Initial State of the AST) (Initial State of the Constraints) (Inference Process) ---Solution--- (Solution) ---Type-checked expression--- (Typed AST)
132. *OJUJBM
     4UBUF
     PG
     UIF
     "45 ---Initial constraints for the given expression— (call_expr type='$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 EFDM
     SFG
     JE $T0 $T1
133. *OJUJBM
     4UBUF
     PG
     UIF
     "45 ---Initial constraints for the given expression— (call_expr type='$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 EFDM
     SFG
     JE $T0 $T1
134. *OJUJBM
     4UBUF
     PG
     UIF
     "45 ---Initial constraints for the given expression— (call_expr type='$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 EFDM
     SFG
     JE $T0 $T1
135. *OJUJBM
     4UBUF
     PG
     UIF
     "45 ---Initial constraints for the given expression— (call_expr type='$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 EFDM
     SFG
     JE $T0 $T1
136. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
137. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
138. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
139. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
140. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
141. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
142. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
143. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
144. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
145. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
146. *OJUJBM
     4UBUF
     PG
     UIF
     $POTUSBJOUT Score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Contextual Type: Int at [code.swift:5:12 - line:5:12] Type Variables: $T0 [allows bindings to: lvalue, noescape] [attributes: delayed] [with possible bindings: <empty>] @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 [allows bindings to: noescape] [attributes: delayed] [with possible bindings: (subtypes of) Int] @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Inactive Constraints: disjunction @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift: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 [Call@code.swift:5:18 → apply function] $T1 conv Int @ locator@0x11b81aec8 [Call@code.swift:5:18 → contextual type]
147. *OGFSFODF
     1SPDFTT (attempting type variable binding $T1 := Int ... (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (found solution: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0>) ) (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (outcome: error) ) ) 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
148. *OGFSFODF
     1SPDFTT (attempting type variable binding $T1 := Int ... (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (found solution: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0>) ) (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (outcome: error) ) ) 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
149. *OGFSFODF
     1SPDFTT (attempting type variable binding $T1 := Int ... (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (found solution: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0>) ) (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (outcome: error) ) ) 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
150. *OGFSFODF
     1SPDFTT (attempting type variable binding $T1 := Int ... (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (found solution: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0>) ) (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (outcome: error) ) ) 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
151. *OGFSFODF
     1SPDFTT (attempting type variable binding $T1 := Int ... (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (found solution: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0>) ) (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (outcome: error) ) ) 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
152. *OGFSFODF
     1SPDFTT (attempting type variable binding $T1 := Int ... (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:1:6 : () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (found solution: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0>) ) (attempting disjunction choice $T0 bound to decl code. (file).foo()@code.swift:2:6 : () -> Bool @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] ... (outcome: error) ) ) 4UBSU 5
     
     *OU 5
     
     
     
     *OU 5
     
     
     
     #PPM 4VDDFTT 'BJMVSF
153. 4PMVUJPO ---Solution--- Fixed score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Type variables: $T0 as () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 as Int @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Overload choices: locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] with code. (file).foo()@code.swift:1:6 as foo: () -> Int Trailing closure matching: locator@0x11b81afe8 [Call@code.swift:5:18 → apply argument]: forward
154. 4PMVUJPO ---Solution--- Fixed score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Type variables: $T0 as () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 as Int @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Overload choices: locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] with code. (file).foo()@code.swift:1:6 as foo: () -> Int Trailing closure matching: locator@0x11b81afe8 [Call@code.swift:5:18 → apply argument]: forward
155. 4PMVUJPO ---Solution--- Fixed score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0> Type variables: $T0 as () -> Int @ locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] $T1 as Int @ locator@0x11b81adb0 [Call@code.swift:5:18 → function result] $T2 as Int @ locator@0x11b81aef0 [Call@code.swift:5:18 → contextual type → pattern match → pattern match → named pattern decl] Overload choices: locator@0x11b81ac00 [OverloadedDeclRef@code.swift:5:18] with code. (file).foo()@code.swift:1:6 as foo: () -> Int Trailing closure matching: locator@0x11b81afe8 [Call@code.swift:5:18 → apply argument]: forward
156. 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 EFDM
     SFG
     JE () -> Int Int
157. 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 EFDM
     SFG
     JE () -> Int Int
158. 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 EFDM
     SFG
     JE () -> Int Int
159. 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 EFDM
     SFG
     JE () -> Int Int
160. 3FDBQ w 5IF
     CBTJDT
     PG
     UZQF
     JOGFSFODF
     BSF
     VOJ fi DBUJPO
     BOE
     TJNQMJ fi DBUJPO
     PG
     DPOTUSBJOUT
     w 4XJGU
     FYUFOET
     JU
     CZ
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     TFBSDI
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     w 8F
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161. /FYU
     4UFQT w JNQMFNFOUJOH
     UZQF
     JOGFSFODF
     https://stackoverflow.com/questions/415532/implementing-type- inference
     w 5ZQF
     $IFDLFS
     %FTJHO
     BOE
     *NQMFNFOUBUJPO
     https://github.com/apple/swift/blob/main/docs/TypeChecker.md
     w 4XJGU5ZQF*OGFSFODF)BOET0O
     https://github.com/omochi/SwiftTypeInferenceHandsOn w $PNQJMJOH
     4XJGU
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     *
     https://forums.swift.org/t/compiling-swift-generics-part-i/60898