src/vs/editor/contrib/parameterHints/browser/parameterHintsModel.ts/ParameterHintsModel/onDidType
class ParameterHintsModel:	private onDidType(text: string) {
		if (!this.triggerOnType) {
			return;
		}

		const lastCharIndex = text.length - 1;
		const triggerCharCode = text.charCodeAt(lastCharIndex);

		if (this.triggerChars.has(triggerCharCode) || this.isTriggered && this.retriggerChars.has(triggerCharCode)) {
			this.trigger({
				triggerKind: languages.SignatureHelpTriggerKind.TriggerCharacter,
				triggerCharacter: text.charAt(lastCharIndex),
			});
		}
	}