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[Sema] Fix SR-1681 spurious "unused result" warning #4625

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Merged
merged 2 commits into from
Sep 6, 2016
Merged

[Sema] Fix SR-1681 spurious "unused result" warning #4625

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c97ebb0
[Sema] Fix SR-1681: spurious "unused result" warning in Swift 3
timbodeit Sep 4, 2016
7c0f9ae
[test] Add test cases for SR-1681 - spurious "unused result" warning
timbodeit Sep 4, 2016
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5 changes: 4 additions & 1 deletion lib/Sema/TypeCheckStmt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1080,9 +1080,12 @@ void TypeChecker::checkIgnoredExpr(Expr *E) {
// If we have an OptionalEvaluationExpr at the top level, then someone is
// "optional chaining" and ignoring the result. Produce a diagnostic if it
// doesn't make sense to ignore it.
if (auto *OEE = dyn_cast<OptionalEvaluationExpr>(valueE))
if (auto *OEE = dyn_cast<OptionalEvaluationExpr>(valueE)) {
if (auto *IIO = dyn_cast<InjectIntoOptionalExpr>(OEE->getSubExpr()))
return checkIgnoredExpr(IIO->getSubExpr());
if (auto *C = dyn_cast<CallExpr>(OEE->getSubExpr()))
return checkIgnoredExpr(C);
}

// Check if we have a call to a function not marked with
// '@discardableResult'.
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38 changes: 38 additions & 0 deletions test/attr/attr_discardableResult.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,11 @@ class C1 {

func f2() -> Int { }

@discardableResult
func f1Optional() -> Int? { }

func f2Optional() -> Int? { }

@discardableResult
func me() -> Self { return self }

Expand All @@ -68,6 +73,10 @@ func testFunctionsInClass(c1 : C1, c2: C2) {
c1.f2() // expected-warning {{result of call to 'f2()' is unused}}
_ = c1.f2() // okay

c1.f1Optional() // okay
c1.f2Optional() // expected-warning {{result of call to 'f2Optional()' is unused}}
_ = c1.f2Optional() // okay

c1.me() // okay
c2.me() // okay

Expand All @@ -91,6 +100,11 @@ struct S1 {
func f1() -> Int { }

func f2() -> Int { }

@discardableResult
func f1Optional() -> Int? { }

func f2Optional() -> Int? { }
}

func testFunctionsInStruct(s1 : S1) {
Expand All @@ -106,6 +120,10 @@ func testFunctionsInStruct(s1 : S1) {
s1.f1() // okay
s1.f2() // expected-warning {{result of call to 'f2()' is unused}}
_ = s1.f2() // okay

s1.f1Optional() // okay
s1.f2Optional() // expected-warning {{result of call to 'f2Optional()' is unused}}
_ = s1.f2Optional() // okay
}

protocol P1 {
Expand Down Expand Up @@ -138,3 +156,23 @@ class X {
@objc
func h() -> Int { }
}

func testOptionalChaining(c1: C1?, s1: S1?) {
c1?.f1() // okay
c1!.f1() // okay
c1?.f1Optional() // okay
c1!.f1Optional() // okay
c1?.f2() // expected-warning {{result of call to 'f2()' is unused}}
c1!.f2() // expected-warning {{result of call to 'f2()' is unused}}
c1?.f2Optional() // expected-warning {{result of call to 'f2Optional()' is unused}}
c1!.f2Optional() // expected-warning {{result of call to 'f2Optional()' is unused}}

s1?.f1() // okay
s1!.f1() // okay
s1?.f1Optional() // okay
s1!.f1Optional() // okay
s1?.f2() // expected-warning {{result of call to 'f2()' is unused}}
s1!.f2() // expected-warning {{result of call to 'f2()' is unused}}
s1?.f2Optional() // expected-warning {{result of call to 'f2Optional()' is unused}}
s1!.f2Optional() // expected-warning {{result of call to 'f2Optional()' is unused}}
}