Allow return to be omitted from single expression functions. #23251

nate-chandler · 2019-03-12T23:06:39Z

Enables return to be omitted from function bodies which consist of only a single expression.

nate-chandler · 2019-03-12T23:06:54Z

@swift-ci please test source compatibility

nate-chandler · 2019-03-13T18:33:01Z

@swift-ci please test source compatibility

nate-chandler · 2019-03-14T19:06:59Z

@swift-ci please test source compatibility

lib/AST/ASTWalker.cpp

lib/AST/Decl.cpp

lib/Parse/ParseDecl.cpp

test/Parse/omit_return.swift

lib/Sema/TypeCheckStmt.cpp

jrose-apple · 2019-03-15T17:55:21Z

Forgot the summary at the top of "This looks pretty good; I'm glad it doesn't seem to take too many changes; good job listing out test cases."

Some other things to check:

code completion (as you mentioned)
what these look like when using SwiftSyntax

lib/Sema/TypeCheckStmt.cpp

lib/Parse/ParseDecl.cpp

nate-chandler · 2019-03-16T00:47:54Z

@swift-ci please test source compatibility

nate-chandler · 2019-03-18T21:42:41Z

@swift-ci please test source compatibility

nate-chandler · 2019-03-21T19:49:22Z

@swift-ci please test source compatibility

nate-chandler · 2019-03-22T17:22:08Z

@swift-ci please test source compatibility

test/FixCode/fixits-omit-return.swift

lib/Sema/TypeCheckStmt.cpp

nate-chandler · 2019-03-25T19:31:20Z

@swift-ci please test

swift-ci · 2019-03-25T19:33:38Z

Build failed
Swift Test Linux Platform
Git Sha - 0a5e8f7

swift-ci · 2019-03-25T19:35:47Z

Build failed
Swift Test OS X Platform
Git Sha - 0a5e8f7

nate-chandler · 2019-03-26T18:21:45Z

@swift-ci please test

swift-ci · 2019-03-26T18:24:05Z

Build failed
Swift Test Linux Platform
Git Sha - a7daf25

swift-ci · 2019-03-26T18:47:48Z

Build failed
Swift Test OS X Platform
Git Sha - a7daf25

nate-chandler · 2019-03-26T23:41:23Z

@swift-ci please test

swift-ci · 2019-03-26T23:43:29Z

Build failed
Swift Test Linux Platform
Git Sha - f0ef9e3

nate-chandler · 2019-03-26T23:50:53Z

@swift-ci please test source compatibility

Match the behavior of typeCheckExpressionImpl which simply calls solve and applySolution but never salvage.

When type-checking a return statement's result, pass a new ContextualTypePurpose when that return statement appears in a function with a single expression. When solving the corresponding constraint system, the conversion constraint will have a new ConstraintKind. When matching types, check whether the constraint kind is this new kind, meaning that the constraint is between a function's single expression and the function's result. If it is, allow a conversion from an uninhabited type (the expression's type) to anything (the function's result type) by adding an uninhabited upcast restriction to the vector of conversions. Finally, at coercion time, upon encountering this restriction, call coerceUninhabited, replacing the original expression with an UninhabitedUpcastExpr. Finally, at SILGen time, treat this UninhabitedUpcastExpr as a ForcedCheckedCastExpr. Eliminates the bare ConstraintSystem usage from typeCheckFunctionBodyUntil, ensuring that the same code path is followed for all function bodies.

Modified so that single-expression implicit return does not throw off tests.

Added objc_interop requirement to tests which require it and moved one test into file stating that requirement.

…l type of single expr function

…f single expr function

Corrected a number of diagnostic regressions.

nate-chandler · 2019-04-24T18:08:37Z

@swift-ci please test

swift-ci · 2019-04-24T18:10:57Z

Build failed
Swift Test Linux Platform
Git Sha - e30511bdb8d8b4f0adc1b75e0db66992f4e25a74

swift-ci · 2019-04-24T18:12:39Z

Build failed
Swift Test OS X Platform
Git Sha - e30511bdb8d8b4f0adc1b75e0db66992f4e25a74

nate-chandler · 2019-04-24T22:38:25Z

@swift-ci Please clean smoke test OS X platform

nate-chandler · 2019-04-24T23:38:10Z

@swift-ci please clean smoke test OS X platform

nate-chandler · 2019-04-25T00:41:27Z

@swift-ci please clean test OS X platform

compnerd · 2019-04-25T20:49:13Z

@nate-chandler this broke the Windows test suite!

plotfi · 2019-04-25T20:51:05Z

test/PlaygroundTransform/implicit_return_never.swift

+// RUN: cp %s %t/main.swift
+// RUN: %target-build-swift -Xfrontend -playground -Xfrontend -disable-playground-transform -o %t/main %t/main.swift
+// RUN: %target-codesign %t/main
+// RUN: ! %target-run %t/main --crash 2>&1 | %FileCheck -check-prefix=CRASH-CHECK %s


Please use not.py next time.

I think we prefer LLVM's not --crash.

slavapestov · 2019-05-03T20:25:45Z

lib/SILOptimizer/Mandatory/DataflowDiagnostics.cpp

+  if (numElements > 0) {
+    auto element = BS->getElement(numElements - 1);
+    if (auto expr = element.dyn_cast<Expr *>()) {
+      if (expr->getType()->getCanonicalType() == ResTy->getCanonicalType()) {


TypeBase::isEqual() is a shortcut for comparing getCanonicalType()s

PR with a fix at #24546 .

slavapestov · 2019-05-03T20:26:58Z

lib/Parse/ParseDecl.cpp

+      auto Element = BS->getElement(0);
+      if (auto *stmt = Element.dyn_cast<Stmt *>()) {
+        auto kind = AFD->getKind();
+        if (kind == DeclKind::Var || kind == DeclKind::Subscript ||


AFD is an AbstractFunctionDecl so it will never have a kind that is Var or Subscript. In general we prefer to use isa<> instead of checking the kind directly

PR with a fix at #24546 .

nate-chandler changed the title ~~WIP: Allow return to be omitted from single expression functions.~~ [WIP] Allow return to be omitted from single expression functions. Mar 13, 2019

AnnaZaks requested review from jrose-apple and DougGregor March 15, 2019 17:26

jrose-apple reviewed Mar 15, 2019

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jrose-apple reviewed Mar 16, 2019

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benlangmuir reviewed Mar 16, 2019

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nate-chandler changed the title ~~[WIP] Allow return to be omitted from single expression functions.~~ Allow return to be omitted from single expression functions. Mar 21, 2019

nate-chandler marked this pull request as ready for review March 21, 2019 22:10

fassko mentioned this pull request Mar 22, 2019

[131] Issue #131 - April 4, 2019 SwiftWeekly/swiftweekly.github.io#448

Closed

harlanhaskins reviewed Mar 22, 2019

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test/FixCode/fixits-omit-return.swift Outdated Show resolved Hide resolved

jrose-apple reviewed Mar 22, 2019

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nate-chandler force-pushed the nate/omit-return branch from 3d5bb41 to a42c2c1 Compare March 26, 2019 23:40

benlangmuir mentioned this pull request Mar 27, 2019

[code-completion] Add type context for single-expression function bodies #23587

Merged

nate-chandler and others added 17 commits April 24, 2019 09:59

Used expected-error to test fixit.

859ffdc

Added PlaygroundTransform tests on implicit return.

717e5e4

Don't attempt to apply solution from salvage.

92998f7

Match the behavior of typeCheckExpressionImpl which simply calls solve and applySolution but never salvage.

Tested implicit non/conversion from uninhabited.

5c1537f

Don't add an implicit () after return for initializers.

0b528ae

Corrected tests by removing implicit returns.

c21678d

Replaced superseded test.

1071d97

Tweaked remaining failing tests.

3139d3e

Modified so that single-expression implicit return does not throw off tests.

Fixed up return omission test cases for Linux.

cca301a

Added objc_interop requirement to tests which require it and moved one test into file stating that requirement.

[ConstraintLocator] Add a special locator element to denote contextua…

448e04e

…l type of single expr function

[ConstraintSystem] Use special locator for expr representing return o…

ca6cf0c

…f single expr function

Eliminated conversion from uninhabited.

b2ad562

Don't implicitly return assignments.

a09a964

Corrected a number of diagnostic regressions.

Reverted unneeded test change.

39bbce1

Removed old comment.

843ac0b

Corrected off-by-one error.

f8ef213

nate-chandler force-pushed the nate/omit-return branch from 23ad54a to f8ef213 Compare April 24, 2019 18:08

nate-chandler merged commit 155a155 into swiftlang:master Apr 25, 2019

plotfi reviewed Apr 25, 2019

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slavapestov reviewed May 3, 2019

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maustinstar mentioned this pull request Oct 30, 2020

[SR-11711] [Parse] Single-expression implicit returns within #if declarations #34510

Merged

nate-chandler deleted the nate/omit-return branch July 5, 2023 23:33

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Allow return to be omitted from single expression functions. #23251

Allow return to be omitted from single expression functions. #23251

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Allow return to be omitted from single expression functions. #23251

Allow return to be omitted from single expression functions. #23251

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