Make anyFunctionType a subtype of all function types

[ahejlsberg]

Implements what I discuss here.

Fixes #1016.

[Copilot]

Pull Request Overview

Introduces anyFunctionType as a wildcard subtype of all other function types, updating signature relation logic and test baselines.

• Adds early-return logic in signaturesRelatedTo to treat anyFunctionType as a subtype (but not a supertype) of functions.
• Updates test baselines to reflect that callbacks inferred from useMemo now have parameter type any and trigger an implicit-any error.
• Adjusts symbol and error snapshots to expect any for parameter x.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
internal/checker/relater.go	Added checks to return TernaryTrue/TernaryFalse for anyFunctionType subtyping
testdata/baselines/reference/compiler/subtypeReductionWithAnyFunctionType.types	Updated expected type prints to (x: any) => boolean
testdata/baselines/reference/compiler/subtypeReductionWithAnyFunctionType.symbols	Adjusted symbol entries so x is declared with type any
testdata/baselines/reference/compiler/subtypeReductionWithAnyFunctionType.errors.txt	Now reports a TS7006 implicit-any error for parameter x

[Copilot]

The unconditional TernaryTrue when source is anyFunctionType bypasses signature checks (including return types), which could incorrectly mark incompatible function signatures as subtypes. Consider preserving return-type compatibility or narrowing the early return condition.

Suggested change

	if source == r.c.anyFunctionType {
	if source == r.c.anyFunctionType {
	sourceSignatures := r.c.getSignaturesOfType(source, kind)
	targetSignatures := r.c.getSignaturesOfType(target, kind)
	for _, s := range sourceSignatures {
	for _, t := range targetSignatures {
	if r.signatureRelatedTo(s, t, true /*erase*/, reportErrors, intersectionState) == TernaryFalse {
	return TernaryFalse
	}
	}
	}