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

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

$ swiftc -Xfrontend -debug-constraints code.swift ---Constraint solving at [code.swift:1:21 -

0VUQVUGPSOEJWJEVBMOGFSFODFT ---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)

*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

*OJUJBM4UBUFPGUIF"45 ---Initial constraints for the given expression— (call_expr type='$T1' location=code.swift:5:18

*OJUJBM4UBUFPGUIF$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 [[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]

*OJUJBM4UBUFPGUIF$POTUSBJOUT Score: <default 0 0 0 0 0 0 0

*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: <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 [[email protected]:5:18] ... (outcome: error) ) ) 4UBSU 5*OU 5 *OU 5 #PPM 4VDDFTT 'BJMVSF

*OGFSFODF1SPDFTT (attempting type variable binding $T1 := Int ... (attempting

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 [[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

4PMVUJPO ---Solution--- Fixed score: <default 0 0 0 0 0

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

5ZQFE"45 ---Type-checked expression--- (call_expr type=‘Int' location=code.swift:5:18 range=[code.swift:5:18 - line:5:22] isolationCrossing=none

3FDBQ w 5IFCBTJDTPGUZQFJOGFSFODFBSFVOJ fi DBUJPOBOETJNQMJ fi DBUJPOPG DPOTUSBJOUT w 4XJGUFYUFOETJUCZBEEJOHTFBSDIUPUIFQSPDFTT

w 8FDBOVOEFSTUBOEJUTPQFSBUJPOTCZMPPLJOHBUUIFDPNQJMFSTPVUQVU

/FYU4UFQT w JNQMFNFOUJOHUZQFJOGFSFODF https://stackoverflow.com/questions/415532/implementing-type- inference w 5ZQF$IFDLFS%FTJHOBOENQMFNFOUBUJPO https://github.com/apple/swift/blob/main/docs/TypeChecker.md w 4XJGU5ZQFOGFSFODF)BOET0O

https://github.com/omochi/SwiftTypeInferenceHandsOn w $PNQJMJOH4XJGUHFOFSJDT 1BSU* https://forums.swift.org/t/compiling-swift-generics-part-i/60898

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

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

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