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Merged
Daniel Rosenwasser (DanielRosenwasser) merged 9 commits into from
Mar 17, 2023
Merged

Allow implicit return with explicit undefined return type #53092

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3bee8eb
Allow implicit return with explicit `undefined` return type
saschanaz Mar 4, 2023
17b43e5
Update tests/baselines/reference/functionsMissingReturnStatementsAndE…
saschanaz Mar 6, 2023
b267f96
Reflect feedback
saschanaz Mar 6, 2023
e38cd2d
allowUnreachableCode is redundant
saschanaz Mar 6, 2023
03c6cb5
Revise the error
saschanaz Mar 6, 2023
ec64119
Merge branch 'main' into return-undefined
saschanaz Mar 6, 2023
1eed970
Update baselines
saschanaz Mar 6, 2023
168fa04
Merge remote-tracking branch 'upstream/main' into return-undefined
saschanaz Mar 17, 2023
5632662
Split error messages
saschanaz Mar 17, 2023
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8 changes: 4 additions & 4 deletions src/compiler/checker.ts
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Expand Up @@ -35469,8 +35469,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
const functionFlags = getFunctionFlags(func);
const type = returnType && unwrapReturnType(returnType, functionFlags);

// Functions with with an explicitly specified 'void' or 'any' return type don't need any return expressions.
if (type && maybeTypeOfKind(type, TypeFlags.Any | TypeFlags.Void)) {
// Functions with an explicitly specified 'undefined, 'void' or 'any' return type don't need any return expressions.
if (type && maybeTypeOfKind(type, TypeFlags.Undefined | TypeFlags.Void | TypeFlags.Any)) {
return;
}

Expand All @@ -35489,9 +35489,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
else if (type && !hasExplicitReturn) {
// minimal check: function has syntactic return type annotation and no explicit return statements in the body
// this function does not conform to the specification.
error(errorNode, Diagnostics.A_function_whose_declared_type_is_neither_void_nor_any_must_return_a_value);
error(errorNode, Diagnostics.A_function_whose_declared_type_is_neither_void_nor_any_must_return_a_value_undefined_is_also_allowed_with_strictNullChecks);
}
else if (type && strictNullChecks && !isTypeAssignableTo(undefinedType, type)) {
else if (type && strictNullChecks) {
error(errorNode, Diagnostics.Function_lacks_ending_return_statement_and_return_type_does_not_include_undefined);
}
else if (compilerOptions.noImplicitReturns) {
Expand Down
4 changes: 2 additions & 2 deletions src/compiler/diagnosticMessages.json
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Expand Up @@ -1868,7 +1868,7 @@
"category": "Error",
"code": 2354
},
"A function whose declared type is neither 'void' nor 'any' must return a value.": {
"A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.": {

@jakebailey Jake Bailey (jakebailey) Mar 17, 2023

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I think I'd rather us duplicate this message to have two (Daniel Rosenwasser (@DanielRosenwasser) may be able to better write these):

A function whose declared type is neither 'void' nor 'any' must return a value.

A function whose declared type is not 'void', 'any', or 'undefined' must return a value.

Then, conditionally emit one based on the variable strictNullChecks.

Then below in codefixes/returnValueCorrect.ts, handle both.

"category": "Error",
"code": 2355
},
Expand Down Expand Up @@ -6706,7 +6706,7 @@
"category": "Suggestion",
"code": 80010
},

"Add missing 'super()' call": {
"category": "Message",
"code": 90001
Expand Down
4 changes: 2 additions & 2 deletions src/services/codefixes/returnValueCorrect.ts
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Expand Up @@ -51,7 +51,7 @@ const fixIdAddReturnStatement = "fixAddReturnStatement";
const fixRemoveBracesFromArrowFunctionBody = "fixRemoveBracesFromArrowFunctionBody";
const fixIdWrapTheBlockWithParen = "fixWrapTheBlockWithParen";
const errorCodes = [
Diagnostics.A_function_whose_declared_type_is_neither_void_nor_any_must_return_a_value.code,
Diagnostics.A_function_whose_declared_type_is_neither_void_nor_any_must_return_a_value_undefined_is_also_allowed_with_strictNullChecks.code,
Diagnostics.Type_0_is_not_assignable_to_type_1.code,
Diagnostics.Argument_of_type_0_is_not_assignable_to_parameter_of_type_1.code
];
Expand Down Expand Up @@ -213,7 +213,7 @@ function getInfo(checker: TypeChecker, sourceFile: SourceFile, position: number,

const declaration = findAncestor(node.parent, isFunctionLikeDeclaration);
switch (errorCode) {
case Diagnostics.A_function_whose_declared_type_is_neither_void_nor_any_must_return_a_value.code:
case Diagnostics.A_function_whose_declared_type_is_neither_void_nor_any_must_return_a_value_undefined_is_also_allowed_with_strictNullChecks.code:
if (!declaration || !declaration.body || !declaration.type || !rangeContainsRange(declaration.type, node)) return undefined;
return getFixInfo(checker, declaration, checker.getTypeFromTypeNode(declaration.type), /* isFunctionType */ false);
case Diagnostics.Argument_of_type_0_is_not_assignable_to_parameter_of_type_1.code:
Expand Down
4 changes: 2 additions & 2 deletions tests/baselines/reference/ParameterList5.errors.txt
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@@ -1,12 +1,12 @@
tests/cases/compiler/ParameterList5.ts(1,15): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/compiler/ParameterList5.ts(1,15): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
tests/cases/compiler/ParameterList5.ts(1,16): error TS2369: A parameter property is only allowed in a constructor implementation.
tests/cases/compiler/ParameterList5.ts(1,29): error TS2304: Cannot find name 'C'.


==== tests/cases/compiler/ParameterList5.ts (3 errors) ====
function A(): (public B) => C {
~~~~~~~~~~~~~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
~~~~~~~~
!!! error TS2369: A parameter property is only allowed in a constructor implementation.
~
Expand Down
8 changes: 4 additions & 4 deletions tests/baselines/reference/asyncFunctionDeclaration15_es5.errors.txt
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@@ -1,8 +1,8 @@
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(6,23): error TS1055: Type '{}' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(6,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(6,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(7,23): error TS1055: Type 'any' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(8,23): error TS1055: Type 'number' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(8,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(8,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(9,23): error TS1055: Type 'PromiseLike' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration15_es5.ts(10,23): error TS1055: Type 'typeof Thenable' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
Construct signature return types 'Thenable' and 'PromiseLike<T>' are incompatible.
Expand All @@ -22,15 +22,15 @@ tests/cases/conformance/async/es5/functionDeclarations/asyncFunctionDeclaration1
~~~
!!! error TS1055: Type '{}' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
async function fn3(): any { } // error
~~~
!!! error TS1055: Type 'any' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
async function fn4(): number { } // error
~~~~~~
!!! error TS1055: Type 'number' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
~~~~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
async function fn5(): PromiseLike<void> { } // error
~~~~~~~~~~~~~~~~~
!!! error TS1055: Type 'PromiseLike' is not a valid async function return type in ES5/ES3 because it does not refer to a Promise-compatible constructor value.
Expand Down
8 changes: 4 additions & 4 deletions tests/baselines/reference/asyncFunctionDeclaration15_es6.errors.txt
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@@ -1,8 +1,8 @@
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(6,23): error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<{}>'?
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(6,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(6,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(7,23): error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<any>'?
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(8,23): error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<number>'?
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(8,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(8,23): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(9,23): error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<void>'?
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(10,23): error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<void>'?
tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(17,16): error TS1058: The return type of an async function must either be a valid promise or must not contain a callable 'then' member.
Expand All @@ -19,15 +19,15 @@ tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration1
~~~
!!! error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<{}>'?
~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
async function fn3(): any { } // error
~~~
!!! error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<any>'?
async function fn4(): number { } // error
~~~~~~
!!! error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<number>'?
~~~~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
async function fn5(): PromiseLike<void> { } // error
~~~~~~~~~~~~~~~~~
!!! error TS1064: The return type of an async function or method must be the global Promise<T> type. Did you mean to write 'Promise<void>'?
Expand Down
8 changes: 4 additions & 4 deletions tests/baselines/reference/conflictingTypeAnnotatedVar.errors.txt
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@@ -1,10 +1,10 @@
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(1,5): error TS2300: Duplicate identifier 'foo'.
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(2,10): error TS2300: Duplicate identifier 'foo'.
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(2,10): error TS2393: Duplicate function implementation.
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(2,17): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(2,17): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(3,10): error TS2300: Duplicate identifier 'foo'.
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(3,10): error TS2393: Duplicate function implementation.
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(3,17): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/compiler/conflictingTypeAnnotatedVar.ts(3,17): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.


==== tests/cases/compiler/conflictingTypeAnnotatedVar.ts (7 errors) ====
Expand All @@ -17,11 +17,11 @@ tests/cases/compiler/conflictingTypeAnnotatedVar.ts(3,17): error TS2355: A funct
~~~
!!! error TS2393: Duplicate function implementation.
~~~~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
function foo(): number { }
~~~
!!! error TS2300: Duplicate identifier 'foo'.
~~~
!!! error TS2393: Duplicate function implementation.
~~~~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
4 changes: 2 additions & 2 deletions tests/baselines/reference/controlFlowGenericTypes.errors.txt
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Expand Up @@ -2,7 +2,7 @@ tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(49,15): error TS2
tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(55,15): error TS2345: Argument of type 'undefined' is not assignable to parameter of type 'Box<unknown>'.
tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(81,11): error TS2339: Property 'foo' does not exist on type 'MyUnion'.
Property 'foo' does not exist on type 'AA'.
tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(90,44): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(90,44): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(91,11): error TS2339: Property 'foo' does not exist on type 'MyUnion'.
Property 'foo' does not exist on type 'AA'.
tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(156,16): error TS18048: 'obj' is possibly 'undefined'.
Expand Down Expand Up @@ -109,7 +109,7 @@ tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(168,9): error TS1

const fn2 = <T extends MyUnion>(value: T): MyUnion => {
~~~~~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.
value.foo; // Error
~~~
!!! error TS2339: Property 'foo' does not exist on type 'MyUnion'.
Expand Down
4 changes: 2 additions & 2 deletions tests/baselines/reference/errorOnContextuallyTypedReturnType.errors.txt
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@@ -1,6 +1,6 @@
tests/cases/compiler/errorOnContextuallyTypedReturnType.ts(1,5): error TS2322: Type '() => void' is not assignable to type '() => boolean'.
Type 'void' is not assignable to type 'boolean'.
tests/cases/compiler/errorOnContextuallyTypedReturnType.ts(2,37): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
tests/cases/compiler/errorOnContextuallyTypedReturnType.ts(2,37): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.


==== tests/cases/compiler/errorOnContextuallyTypedReturnType.ts (2 errors) ====
Expand All @@ -10,5 +10,5 @@ tests/cases/compiler/errorOnContextuallyTypedReturnType.ts(2,37): error TS2355:
!!! error TS2322: Type 'void' is not assignable to type 'boolean'.
var n2: () => boolean = function ():boolean { }; // expect an error here
~~~~~~~
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value.
!!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. 'undefined' is also allowed with --strictNullChecks.

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