Infer void for statement-less function bodies in isolatedDeclarations syntactic inference

internal/checker/pseudotypenodebuilder.go

@@ -171,6 +171,8 @@ func (b *NodeBuilderImpl) pseudoTypeToNode(t *pseudochecker.PseudoType) *ast.Nod
 		return b.f.NewLiteralTypeNode(b.f.NewKeywordExpression(ast.KindFalseKeyword))
 	case pseudochecker.PseudoTypeKindTrue:
 		return b.f.NewLiteralTypeNode(b.f.NewKeywordExpression(ast.KindTrueKeyword))
+	case pseudochecker.PseudoTypeKindVoid:
+		return b.f.NewKeywordTypeNode(ast.KindVoidKeyword)
 	case pseudochecker.PseudoTypeKindSingleCallSignature:
 		d := t.AsPseudoTypeSingleCallSignature()
 		signature := b.ch.getSignatureFromDeclaration(d.Signature)
@@ -744,6 +746,8 @@ func (b *NodeBuilderImpl) pseudoTypeToType(t *pseudochecker.PseudoType) *Type {
 		return b.ch.falseType
 	case pseudochecker.PseudoTypeKindTrue:
 		return b.ch.trueType
+	case pseudochecker.PseudoTypeKindVoid:
+		return b.ch.voidType
 	case pseudochecker.PseudoTypeKindStringLiteral, pseudochecker.PseudoTypeKindNumericLiteral, pseudochecker.PseudoTypeKindBigIntLiteral:
 		source := t.AsPseudoTypeLiteral().Node
 		return b.ch.getRegularTypeOfExpression(source) // big shortcut, uses cached expression types where possible

internal/fourslash/_scripts/failingTests.txt

@@ -63,10 +63,14 @@ TestCodeFixInferFromUsageRestParam3
 TestCodeFixInferFromUsageVariable3JS
 TestCodeFixMissingTypeAnnotationOnExports11
 TestCodeFixMissingTypeAnnotationOnExports16
+TestCodeFixMissingTypeAnnotationOnExports22_formatting
 TestCodeFixMissingTypeAnnotationOnExports23_heritage_formatting
 TestCodeFixMissingTypeAnnotationOnExports24_heritage_formatting_2
 TestCodeFixMissingTypeAnnotationOnExports25_heritage_formatting_3
 TestCodeFixMissingTypeAnnotationOnExports28_long_types
+TestCodeFixMissingTypeAnnotationOnExports33_methods
+TestCodeFixMissingTypeAnnotationOnExports43_expando_functions_2
+TestCodeFixMissingTypeAnnotationOnExports46_decorators_experimental
 TestCodeFixSpelling4
 TestCodeFixSpelling5
 TestCodeFixSpellingCaseSensitive1

internal/pseudochecker/lookup.go

@@ -226,6 +226,9 @@ func (ch *PseudoChecker) typeFromSingleReturnExpression(fn *ast.Node) *PseudoTyp
 
 		body := fn.Body()
 		if ast.IsBlock(body) {
+			if len(body.Statements()) == 0 {
+				return PseudoTypeVoid
+			}
 			ast.ForEachReturnStatement(body, func(stmt *ast.Node) bool {
 				if stmt.Parent != body { // Why bail on nested return statements?
 					candidateExpr = nil

internal/pseudochecker/type.go

@@ -33,6 +33,7 @@ const (
 	PseudoTypeKindBoolean
 	PseudoTypeKindFalse
 	PseudoTypeKindTrue
+	PseudoTypeKindVoid
 	PseudoTypeKindSingleCallSignature
 	PseudoTypeKindTuple
 	PseudoTypeKindObjectLiteral
@@ -77,6 +78,7 @@ var (
 	PseudoTypeBoolean   = newPseudoType(PseudoTypeKindBoolean, &PseudoTypeBase{})
 	PseudoTypeFalse     = newPseudoType(PseudoTypeKindFalse, &PseudoTypeBase{})
 	PseudoTypeTrue      = newPseudoType(PseudoTypeKindTrue, &PseudoTypeBase{})
+	PseudoTypeVoid      = newPseudoType(PseudoTypeKindVoid, &PseudoTypeBase{})
 )
 
 // PseudoTypeDirect directly encodes the type referred to by a given TypeNode

testdata/baselines/reference/submodule/compiler/isolatedDeclarationErrors.errors.txt

@@ -2,12 +2,11 @@ isolatedDeclarationErrors.ts(2,1): error TS9023: Assigning properties to functio
 isolatedDeclarationErrors.ts(2,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 isolatedDeclarationErrors.ts(5,1): error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
 isolatedDeclarationErrors.ts(5,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-isolatedDeclarationErrors.ts(7,30): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrors.ts(8,1): error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
 isolatedDeclarationErrors.ts(8,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 
 
-==== isolatedDeclarationErrors.ts (7 errors) ====
+==== isolatedDeclarationErrors.ts (6 errors) ====
     function errorOnAssignmentBelowDecl(): void {}
     errorOnAssignmentBelowDecl.a = "";
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -23,10 +22,6 @@ isolatedDeclarationErrors.ts(8,1): error TS9013: Expression type can't be inferr
 !!! error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 
     const errorOnMissingReturn = () => {}
-                                 ~~~~~~~~
-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9027 isolatedDeclarationErrors.ts:7:7: Add a type annotation to the variable errorOnMissingReturn.
-!!! related TS9030 isolatedDeclarationErrors.ts:7:30: Add a return type to the function expression.
     errorOnMissingReturn.a = "";
     ~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.

testdata/baselines/reference/submodule/compiler/isolatedDeclarationErrorsClasses.errors.txt

@@ -1,5 +1,4 @@
 isolatedDeclarationErrorsClasses.ts(3,5): error TS9012: Property must have an explicit type annotation with --isolatedDeclarations.
-isolatedDeclarationErrorsClasses.ts(4,5): error TS9008: Method must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsClasses.ts(8,18): error TS7006: Parameter 'p' implicitly has an 'any' type.
 isolatedDeclarationErrorsClasses.ts(8,18): error TS9011: Parameter must have an explicit type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsClasses.ts(9,23): error TS9011: Parameter must have an explicit type annotation with --isolatedDeclarations.
@@ -11,7 +10,6 @@ isolatedDeclarationErrorsClasses.ts(36,5): error TS9038: Computed property names
 isolatedDeclarationErrorsClasses.ts(36,6): error TS2304: Cannot find name 'missing'.
 isolatedDeclarationErrorsClasses.ts(38,5): error TS9038: Computed property names on class or object literals cannot be inferred with --isolatedDeclarations.
 isolatedDeclarationErrorsClasses.ts(40,5): error TS9038: Computed property names on class or object literals cannot be inferred with --isolatedDeclarations.
-isolatedDeclarationErrorsClasses.ts(42,5): error TS9008: Method must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsClasses.ts(42,5): error TS9038: Computed property names on class or object literals cannot be inferred with --isolatedDeclarations.
 isolatedDeclarationErrorsClasses.ts(44,5): error TS9038: Computed property names on class or object literals cannot be inferred with --isolatedDeclarations.
 isolatedDeclarationErrorsClasses.ts(44,35): error TS7006: Parameter 'v' implicitly has an 'any' type.
@@ -26,17 +24,14 @@ isolatedDeclarationErrorsClasses.ts(56,5): error TS7010: '[noAnnotationLiteralNa
 isolatedDeclarationErrorsClasses.ts(56,5): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 
 
-==== isolatedDeclarationErrorsClasses.ts (26 errors) ====
+==== isolatedDeclarationErrorsClasses.ts (24 errors) ====
     export class Cls {
 
         field = 1 + 1;
         ~~~~~
 !!! error TS9012: Property must have an explicit type annotation with --isolatedDeclarations.
 !!! related TS9029 isolatedDeclarationErrorsClasses.ts:3:5: Add a type annotation to the property field.
         method() {}
-        ~~~~~~
-!!! error TS9008: Method must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9034 isolatedDeclarationErrorsClasses.ts:4:5: Add a return type to the method
 
         methodOk(): void {}
 
@@ -103,9 +98,6 @@ isolatedDeclarationErrorsClasses.ts(56,5): error TS9013: Expression type can't b
 
         [noAnnotationStringName]() { }
         ~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS9008: Method must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9034 isolatedDeclarationErrorsClasses.ts:42:5: Add a return type to the method
-        ~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS9038: Computed property names on class or object literals cannot be inferred with --isolatedDeclarations.
 
         [noParamAnnotationStringName](v): void { }

testdata/baselines/reference/submodule/compiler/isolatedDeclarationErrorsExpandoFunctions.errors.txt

@@ -1,70 +1,46 @@
-isolatedDeclarationErrorsExpandoFunctions.ts(1,17): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsExpandoFunctions.ts(3,1): error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
 isolatedDeclarationErrorsExpandoFunctions.ts(3,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-isolatedDeclarationErrorsExpandoFunctions.ts(3,13): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsExpandoFunctions.ts(4,1): error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
 isolatedDeclarationErrorsExpandoFunctions.ts(4,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-isolatedDeclarationErrorsExpandoFunctions.ts(4,12): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsExpandoFunctions.ts(5,1): error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
 isolatedDeclarationErrorsExpandoFunctions.ts(5,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-isolatedDeclarationErrorsExpandoFunctions.ts(5,12): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsExpandoFunctions.ts(6,1): error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
 isolatedDeclarationErrorsExpandoFunctions.ts(6,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-isolatedDeclarationErrorsExpandoFunctions.ts(6,14): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsExpandoFunctions.ts(7,1): error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
 isolatedDeclarationErrorsExpandoFunctions.ts(7,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-isolatedDeclarationErrorsExpandoFunctions.ts(7,16): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsExpandoFunctions.ts(8,1): error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
 isolatedDeclarationErrorsExpandoFunctions.ts(8,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 isolatedDeclarationErrorsExpandoFunctions.ts(9,1): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 
 
-==== isolatedDeclarationErrorsExpandoFunctions.ts (19 errors) ====
+==== isolatedDeclarationErrorsExpandoFunctions.ts (13 errors) ====
     export function foo() {}
-                    ~~~
-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9031 isolatedDeclarationErrorsExpandoFunctions.ts:1:17: Add a return type to the function declaration.
 
     foo.apply = () => {}
     ~~~~~~~~~
 !!! error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-                ~~~~~~~~
-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9030 isolatedDeclarationErrorsExpandoFunctions.ts:3:13: Add a return type to the function expression.
     foo.call = ()=> {}
     ~~~~~~~~
 !!! error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
     ~~~~~~~~~~~~~~~~~~
 !!! error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-               ~~~~~~~
-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9030 isolatedDeclarationErrorsExpandoFunctions.ts:4:12: Add a return type to the function expression.
     foo.bind = ()=> {}
     ~~~~~~~~
 !!! error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
     ~~~~~~~~~~~~~~~~~~
 !!! error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-               ~~~~~~~
-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9030 isolatedDeclarationErrorsExpandoFunctions.ts:5:12: Add a return type to the function expression.
     foo.caller = ()=> {}
     ~~~~~~~~~~
 !!! error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
     ~~~~~~~~~~~~~~~~~~~~
 !!! error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-                 ~~~~~~~
-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9030 isolatedDeclarationErrorsExpandoFunctions.ts:6:14: Add a return type to the function expression.
     foo.toString = ()=> {}
     ~~~~~~~~~~~~
 !!! error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.
     ~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS9013: Expression type can't be inferred with --isolatedDeclarations.
-                   ~~~~~~~
-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9030 isolatedDeclarationErrorsExpandoFunctions.ts:7:16: Add a return type to the function expression.
     foo.length = 10
     ~~~~~~~~~~
 !!! error TS9023: Assigning properties to functions without declaring them is not supported with --isolatedDeclarations. Add an explicit declaration for the properties assigned to this function.

testdata/baselines/reference/submodule/compiler/isolatedDeclarationErrorsFunctionDeclarations.errors.txt

@@ -1,16 +1,12 @@
-isolatedDeclarationErrorsFunctionDeclarations.ts(1,17): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsFunctionDeclarations.ts(3,35): error TS9011: Parameter must have an explicit type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsFunctionDeclarations.ts(7,49): error TS9011: Parameter must have an explicit type annotation with --isolatedDeclarations.
 isolatedDeclarationErrorsFunctionDeclarations.ts(7,66): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 isolatedDeclarationErrorsFunctionDeclarations.ts(7,81): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 isolatedDeclarationErrorsFunctionDeclarations.ts(9,55): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
 
 
-==== isolatedDeclarationErrorsFunctionDeclarations.ts (6 errors) ====
+==== isolatedDeclarationErrorsFunctionDeclarations.ts (5 errors) ====
     export function noReturn() {}
-                    ~~~~~~~~
-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
-!!! related TS9031 isolatedDeclarationErrorsFunctionDeclarations.ts:1:17: Add a return type to the function declaration.
 
     export function noParamAnnotation(p): void {}
                                       ~

testdata/baselines/reference/submodule/compiler/isolatedDeclarationErrorsFunctionDeclarations.errors.txt.diff

@@ -0,0 +1,20 @@
+--- old.isolatedDeclarationErrorsFunctionDeclarations.errors.txt
++++ new.isolatedDeclarationErrorsFunctionDeclarations.errors.txt
+@@= skipped -0, +0 lines =@@
+-isolatedDeclarationErrorsFunctionDeclarations.ts(1,17): error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
+ isolatedDeclarationErrorsFunctionDeclarations.ts(3,35): error TS9011: Parameter must have an explicit type annotation with --isolatedDeclarations.
+ isolatedDeclarationErrorsFunctionDeclarations.ts(7,49): error TS9011: Parameter must have an explicit type annotation with --isolatedDeclarations.
+ isolatedDeclarationErrorsFunctionDeclarations.ts(7,66): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
+@@= skipped -5, +4 lines =@@
+ isolatedDeclarationErrorsFunctionDeclarations.ts(9,55): error TS9013: Expression type can't be inferred with --isolatedDeclarations.
+
+
+-==== isolatedDeclarationErrorsFunctionDeclarations.ts (6 errors) ====
++==== isolatedDeclarationErrorsFunctionDeclarations.ts (5 errors) ====
+     export function noReturn() {}
+-                    ~~~~~~~~
+-!!! error TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
+-!!! related TS9031 isolatedDeclarationErrorsFunctionDeclarations.ts:1:17: Add a return type to the function declaration.
+
+     export function noParamAnnotation(p): void {}
+                                       ~